Optoelectronics and Fiber Optic Technology [1st ed.] 9780750653701, 0750653701

Citation preview

Optoelectronic and Fiber Optic

Technology

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About the Author

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Ray Tricker (MSc, IEng, FIIE (elec), FinstM, FIQA, MIRSE) as well as being the Principal Consultant and Managing Director of Herne European Consultancy Ltd - a company specializing in ISO 9000 and ISO 14000 Management Systems - is also an established Butterworth-Heinemann author. He served with the Royal Corps of Signals (for a total of 37 years) during which time he held various managerial posts culminating in being appointed as the Chief Engineer of NATO ACE COMSEC. Most of Ray's work since joining Herne has centred on the European railways. He has held a number of posts with the Union International des Chemins de fer (UIC) (e.g. Quality Manager of the European Train Control System (ETCS), European Union (EU) T500 Review Team Leader, European Rail Traffic Management System (ERTMS) Users Group Project Co-ordinator, HEROE Project Co-ordinator) and currently (as well as writing books for Butterworth-Heinemann) he has prepared a complete Quality Management System for the European Rail Research Institute (ERRI) in Holland, and in assisting them in gaining ISO 9000 accreditation. He is also consultant to the Association of American Railroads (AAR) and Transportation Technology Centre Inc. (TTCI) advising them on ISO 9001:2000 compliance and has recently been appointed as a member of a Notified Body (for the harmonization of the trans-European, high speed, railway network).

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To Claire

Optoelectronic and Fiber Optic Technology Ray Tricker

Newnes

OXFORD AMSTERDAM BOSTON LONDON NEW YORK PARIS SAN DIEGO SAN FF~NCISCO SINGAPORE SYDNEY TOKYO

Newnes An i m p r i n t of Elsevier Science Linacre House, Jordan Hill, Oxford OX2 8DP 225 W i l d w o o d Avenue, Woburn, MA 01801-2041 First p u b l i s h e d 2002 C o p y r i g h t 9 2002, Ray Tricker. All rights reserved. The right of Ray Tricker to be identified as the a u t h o r of this w o r k has been asserted in accordance with the Copyright, Designs and Patents Act 1988 All rights reserved. No part of this publication may be reproduced in any material form (including photocopying or storing in any medium by electronic means and whether or not transiently or incidentally to some other use of this publication) without the written permission of the copyright holder except in accordance with the provisions of the Copyright, Designs and Patents Act 1988 or under the terms of a licence issued by the Copyright Licensing Agency Ltd, 90 Tottenham Court Road, London, England W1T 4LP. Applications for the copyright holder's written permission to reproduce any part of this publication should be addressed to the publishers

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British Library Cataloguing in Publication Data

A catalogue record for this book is available from the British Library

Library of Congress Cataloging in Publication Data A catalogue record for this book is available from the Library of Congress ISBN 0 7506 5370 1 For information on all N e w n e s publications visit our website at www. new nespress, com

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Contents Foreword Preface

Acknowledgements 1

xiii xv

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The history of fiber optics

1.1 Background 1.2 Basic principles of optical line transmission 1.3 Advantages of optical fibers and optoelectronic signalling 1.3.1 Immunity to electrical and magnetic fields 1.3.2 Low attenuation 1.3.3 Wide transmission bandwidth 1.3.4 Small physical size and weight 1.3.5 Increased flexibility 1.3.6 Electrical insulation 1.3.7 Immunity to electromagnetic interference and interception 1.3.8 Electrical protection 1.3.9 Analog and digital transmission 1.3.10 Receiver sensitivity 1.4 Disadvantages of optical fibers and optoelectronic signalling 1.4.1 Cost 1.4.2 Jointing and test procedures 1.4.3 Tensile stress 1.4.4 Short links 1.4.5 Fiber losses 1.4.6 Other losses 1.5 Practical applications of optoelectronics 1.5.1 Telephone networks 1.5.2 Urban broadband service networks 1.6 The future of optoelectronics 1.6.1 All-optical network 1.6.2 Computers 1.6.3 Transmission speed 1.6.4 Integration

1 19 23 24 25 25 25 26 27

27 28 28 28 29 29 29 30 30 30 31 32 32 32 33 33 34 34 34

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Contents

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Theory 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 2.10

2.11

2.12 2.13 2.14

2.15 2.16

2.17

2.18

Reflection and refraction Refractive index Total internal reflection 2.3.1 Shell's law Angle of incidence Critical angle Acceptance cone Acceptance angle Numerical aperture Structure of a fiber Modes 2.10.1 Multimode step index 2.10.2 Multimode graded index 2.10.3 Single-mode step index Losses 2.11.1 Attenuation 2.11.2 Absorption 2.11.3 Scattering 2.11.4 Bending losses Optical power and power density Optical fiber input power Dispersion losses 2.14.1 Material dispersion 2.14.2 Waveguide dispersion 2.14.3 Chromatic dispersion Optical transitions in semiconductors 2.15.1 Semiconductor optical transitional mechanisms Usable b a n d w i d t h of optoelectronic transmission systems 2.16.1 Cut-off frequency of an optical fiber 2.16.2 Fiber bandwidth Modulation and demodulation of the subcarrier 2.17.1 Modulation techniques 2.17.2 Frequency modulation 2.17.3 Intensity (power) modulation Signal-to-noise ratio 2.18.1 Optical receiver thermal noise 2.18.2 Quantum noise (of light) 2.18.3 Dark current noise 2.18.4 Laser noise 2.18.5 Mode partition noise 2.18.6 Modal noise (in multimode fibers)

38 39 39 41 45 46 47 48 49 49 51 51 52 52 53 53 53 54 55 57 57 58 58 58 59 61 61

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2.19 Types 2.19.1 2.19.2 2.19.3 2.20 Types 2.20.1 2.20.2 2.20.3 2.20.4 2.20.5 3

of mixers End fire mixers Transmissive mixer Biconical tapered transmissive mixer of multiplexing Fiber multiplexing Electrical multiplexing Wavelength division multiplexing Dense wavelength division multiplexing Time division multiplexing

Fibers and cables 3.1 3.2

3.3 3.4

3.5 3.6

3.7

3.8 3.9 3.10

3.11

Single-mode fiber Multimode fiber 3.2.1 Multimode step index fiber 3.2.2 Multimode graded index fiber Manufacturing processes and designs of optical waveguides Manufacturing techniques 3.4.1 Preparation of the glass preform 3.4.2 Forming the glass rod 3.4.3 Rare earth-doped fibers 3.4.4 Cap sealing Plastic fiber optic cables Cable characteristics and specifications 3.6.1 Tensile strength of the cable 3.6.2 Buffered fiber Types of cable 3.7.1 Tight buffered cable 3.7.2 Loose tube 3.7.3 Slotted core cable Fiber optic cable ducts 3.8.1 Tube identification Cable construction Types of ducted cable 3.10.1 External duct cable 3.10.2 Universal duct cable 3.10.3 Universal ruggedized cable 3.10.4 Water protection 3.10.5 Rodent protection 3.10.6 Metallic armouring 3.10.7 Hazardous environmental cable Installation possibilities 3.11.1 Training

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70 70 71 71 71 72 72 72 74 74

76 77 79 79 81 82 85 85 85 90 90 91 92 93 93 95 95 95 96 97 97 98 99 99 100 100 101 101 102 103 104 105

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4

5

Contents

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T r a n s m i t t e r s - light emitting diodes and lasers

106

4.1 Light source 4.2 Conversion of electrical energy into light waves 4.3 Light emitting diodes 4.3.1 LED preparation 4.4 Types of LED 4.4.1 Edge emitting diodes 4.4.2 High radiance light emitting diodes 4.4.3 Diffused gallium arsenide LEDs emitting at 900 nm 4.4.4 Aluminium gallium arsenide/gallium arsenide (A1GaAs/GaAs) high radiance LEDs emitting a t 830 nm 4.4.5 InGaAsP/InP high radiance LEDs emitting at 1300nm 4.4.6 Indium phosphide 4.5 Laser diodes 4.5.1 Advantages 4.5.2 Disadvantages 4.5.3 Design of a laser diode 4.6 Basic differences between gain-guided (current-induced) and index-guided (built-in waveguide) laser diodes 4.6.1 Types of laser diodes 4.6.2 Microdisks 4.6.3 Multiple signalling

106 106 107 110 111 111 112 112

124 126 128 129

R e c e i v e r s - photodiodes

132

5.1 Conversion of light waves into electrical energy 5.2 Design characteristics of an optical receiver 5.2.1 The PIN photodiode 5.2.2 Avalanche photodiodes 5.2.3 Silicon photodiodes 5.2.4 Germanium photodiodes 5.2.5 Indium gallium arsenide photodiodes 5.3 Types of receiver 5.3.1 Analog fiber optic receiver 5.3.2 Digital fiber optic receiver 5.4 Fiber amplifiers 5.4.1 Laser amplifier repeater 5.4.2 Erbium-doped fiber amplifiers 5.4.3 Erbium-doped fluoride fiber amplifiers 5.4.4 Erbium-doped tellurite fiber amplifiers 5.4.5 Praseodymium-doped fluoride fiber amplifiers 5.4.6 Semiconductor optical amplifier

132 134 134 135 135 136 137 137 137 137 138 139 139 139 140 141 141

113 114 115 116 119 120 122

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6

Connectors and couplers

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142

6.1 Connectors 6.1.1 Connector requirements 6.1.2 Quality of the connector 6.1.3 Connector attenuation 6.1.4 Types of connector 6.2 Couplers 6.2.1 End fire coupling 6.2.2 Lens coupling 6.2.3 Multiport couplers 6.2.4 Coupling losses 6.2.5 Attaching a fiber to a connector 6.2.6 Connecting an optical fiber cable to an LED 6.2.7 Connecting a fiber cable to an integrated circuit 6.3 Fiber jointing techniques 6.3.1 Epoxy splices 6.3.2 Heat-cured epoxy 6.3.3 Room temperature-cured epoxy 6.3.4 Pre-injected epoxy 6.3.5 UV adhesive 6.3.6 Cyanoacrylate adhesive 6.3.7 Anaerobic adhesive 6.3.8 Acrylic adhesive 6.3.9 Crimping 6.3.10 No epoxy and no crimping 6.3.11 Advantages and disadvantages of various types of termination methods 6.4 Splicing 6.4.1 Splice losses 6.4.2 Alignment errors during splicing 6.4.3 Mechanical splicing 6.4.4 Fusion splicing 6.4.5 Closures for fiber optic cables 6.4.6 Repeaters and regenerators

142 143 143 144 145 152 153 154 154 158 160 161 162 165 166 166 167 167 167 167 167 168 168 169

Communication systems

183

7.1 7.2 7.3 7.4

184 187 187 188 189 189 191

Local networks Long-distance networks Telephone networks Data networks 7.4.1 Local area network 7.4.2 Metropolitan area network 7.4.3 Wide area network

169 169 169 171 172 174 179 180

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9

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Contents

7.5 Designing an optical fiber cable system 7.5.1 Fiber versus cable 7.5.2 Digital or analog 7.5.3 ATM versus fast Ethernet 7.5.4 Multiplexing 7.5.5 Channel and cable capacity 7.5.6 Fiber loss 7.5.7 Cable routing 7.5.8 Distribution frames 7.6 Optical path loss budget 7.7 Installation techniques 7.7.1 Storage and handling 7.7.2 Cable laying 7.7.3 Installing fiber optic cables in buildings 7.7.4 Blown optical fiber

191 192 193 194 194 196 196 197 201 201 204 205 206 209 211

Optoelectronic test techniques

216

8.1 Testing fiber optics 8.1.1 Production testing 8.1.2 Installation testing 8.1.3 In-service field testing 8.2 Examples of test equipment 8.2.1 Production test kits 8.2.2 Laser light sources 8.2.3 Power meters 8.2.4 Fiber optic tracers 8.2.5 Power and attenuation measuring test sets 8.2.6 Other field testers 8.2.7 Optical time domain reflectometer 8.2.8 Optical fault locator 8.2.9 OFL versus OTDR 8.2.10 Bandwidth measuring test sets

216 217 218 219 219 22O 220 221 221 223 224 225 23O 231 231

Future developments

233

9.1 9.2 9.3

The global market UK market Development trends 9.3.1 Porous silicon 9.3.2 Ballistic transport 9.3.3 Fluoride glasses

233 235 236 237 237 237

Contents

9.4

9.5

9.6 9.7

9.8

9.9

9.3.4 Polarization 9.3.5 Synchronous optical network 9.3.6 Solitron pulses Lasers and amplifiers 9.4.1 Distributed feedback laser 9.4.2 Tuneable lasers 9.4.3 Rare earth-doped fiber lasers and amplifiers 9.4.4 Modular laser source 9.4.5 Erbium-doped fiber amplifier Fiber cables 9.5.1 Re-emergence of multimode fibers 9.5.2 Moulded-clad single-mode fibers 9.5.3 Multi-core fibers 9.5.4 Encapsulated fibers Moveable fibers 9.6.1 Optical bus Transmission systems 9.7.1 Development trends in higher-order optical fiber transmission systems 9.7.2 Transmitters and receivers 9.7.3 Fiberless transmission 9.7.4 Optical Ether 9.7.5 Optical radio Industry 9.8.1 Leak detection 9.8.2 Optical fiber drill bit temperature monitor 9.8.3 Optical fiber soldering iron 9.8.4 Optical computing 9.8.5 Optical multiplexers 9.8.60pto-isolators 9.8.70ptoelectronic switches 9.8.8 High speed optical switches Military 9.9.1 Laser dazzler 9.9.2 Plastic opto-chips 9.9.3 Fiber optic gyroscope Local government 9.10.1 Optical sensors 9.10.2 Office lighting 9.10.3 Decorations 9.10.4 Fiber optic road signs Medicine 9.11.1 Lasers - medical uses 9.11.2 Flexible fiber optic curvature sensors

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238 238 238 239 240 240 240 241 243 243 243 243 243 244 246 246 246 246 247 248 249 250 250 250 251 251 251 252 252 252 252 253 253 253 255 256 256 256 257 257 258 258 259

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9.10

9.11

xii

Contents

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9.12 Other possibilities 9.12.1 9.12.2 9.12.3 9.12.4

Internet Cars and planes Optical processing and computing Mining

9.13 Conclusion

259 259 260 260 261 261

Appendix A

Optoelectronic and fiber optic standards

263

Appendix B

Fiber optic chronology

276

Glossary

278

Acronyms and abbreviations

290

Books by the same author

300

Useful links

301

Index

305

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Foreword

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During the last couple of decades, fiber optics has become increasingly popular in both commercial and military environments and although optoelectronics is based on a comparatively simple technology, it is nevertheless essential for today's engineers to be aware of the basic fundamentals and capabilities of this modern technique. In order to understand new electronic engineering principles, however, it is usually necessary for the reader to have a thorough technical foundation and for the author to derive and explain mathematical theories and progressively develop formulae, etc. to enable the reader to continue his studies with a complete understanding of the fundamentals surrounding this new technology. Although an understanding of the mathematical principles applicable to optoelectronics is of course necessary, it is the aim of this book to provide only a basic introduction to the basics of optoelectronics. A book that introduces the topic, and then leaves it up to others to provide a more in-depth explanation. A book that is easy to read, hard to put down(!) and (bearing in mind the saying that a picture is worth a thousand words) has lots of diagrams, pictures and graphics to aid understanding. As well as being a background reference manual for practising electronic and telecommunications engineers, technicians and students, it will also serve as a user-friendly overview of this increasingly popular subject, especially to those who would like to get to grips with this new area of communications technology.

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Preface

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For over a century, telegraph and telephone systems have been interconnected via copper cables and radio links and these have formed the basis of all suburban, urban and national telecommunication networks. But although the possibility of using a dielectric rod as a waveguide had been studied during the late 1800s and a paper had actually been written about it in the 1920s, it was not until 1966 that Charles Kao and George Hockham patented the principle of 'information transmission through a transparent dielectric medium' (i.e. glass fiber), that the use of glass fibers actually became a viable proposition. Since then, the development of optical fibers and their enormous bandwidth capability has meant that more and more communication systems are now using fibers to pass optical signals over long distances with very little l o s s - especially when compared with the losses experienced by electrical signals over copper lines. Without doubt this technology, following the development of laser diodes, has now become the preferred method for cable communication. However, in the very early days of fiber it was not evident just how dramatic optoelectronic and fiber optic technology would become, or to what extent it would impact on national and global economies. Indeed, a single glass fiber the thickness of a h u m a n hair can now carry the equivalent of 300 million simultaneous telephone c a l l s - roughly all the phone calls going on in America at any one time. But even though computer capacity is anticipated to increase by 1000-fold in the next decade (and 1 000 000-fold in the decade that follows) it is highly unlikely that an optoelectronic system would be incapable of satisfying these new requirements. In less than 20 years optical fiber has revolutionized the global telecommunications network. With the aim of providing a user-friendly background to this increasingly important technology, this book is structured as follows: Chapter 1 - a description of the history surrounding fiber optics and an introduction to some of the people who were involved in its discovery, use and development. Chapter 2 - an overview of the theory behind optoelectronics. Chapter 3 - a description of the different types of fiber that are available (e.g. single mode, multimode, step index, graded index, glass or plastic),

xvi

Preface

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the manufacturing processes and techniques, cable characteristics and specifications and a look at some of the installation possibilities. Chapter 4 - a description of the optoelectronic transmitter (e.g. LED and laser) used to convert electrical signals into optical energy so that they can be propagated down an optical waveguide. Chapter 5 - a look at the other end of the fiber to see how light energy is received and converted back into an electrical signal by an optoelectronic receiver. Chapter 6 - a look at the method used to connect fibers to transceivers and how fibers can be joined a n d / o r spliced together. Chapter 7 - an overview of how fiber optics are utilized in local, long distance and global telecommunication networks. How an optical fiber cable system is designed and the installation techniques used. Chapter 8 - a look at installation and in-service testing techniques and some of the test equipment that is currently available for installers and system engineers. Chapter 9 - a look into the near and future possibilities associated with optoelectronic and fiber optic technology. New and perceived developments are described and an indication of how government, military and industry are increasingly making use of fiber optics is discussed. These chapters are supported by appendices that list some of the European and International standards currently available and concludes with a list of all the main acronyms and abbreviations associated with the optoelectronic and fiber optic technology, together with a detailed glossary of terms and a full index.

Acknowledgements

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Whilst every effort has been made to contact the copyright holders of the pictures, diagrams and drawings used to illustrate this book, it has not proved possible to make contact in all cases. If we have used your images in this book without permission, then we apologize and would request that you please contact us so that we can ensure that you are given due credit in the next reprint.

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The history of fiber optics

1.1 Background

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For over a century, telegraph and telephone systems have been interconnected via copper cables and radio links and these have formed the basis of all suburban, urban and national telecommunication networks. Although line transmission technology has improved over the years, it was not until the last few decades when revolutionary innovations caused by the development of semiconductors, digitalization and optoelectronics dramatically altered the method, technology and cost effectiveness of communication systems. Of course, the transmission of information by visual means is not an entirely new concept, as man has been sending messages optically for centuries and I suspect that the first form of optical communication was the caveman shaking his fist (an action which left no doubt as to its meaning!). This effective communication used the sun as a light source, the hand as the modulator and the eye as the detector. Optical communication then progressed to flags and smoke signals, which enabled messages to be passed over greater distances.

2 Optoelectronics and Fiber Optic Technology

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From a military perspective, all sorts of signalling techniques have been used by armies in the field. The Greeks had the torch telegraph, the Phoenicians water telegraphs, and the Roman army used coloured smoke as a means of communication. The Greeks and Phoenicians also used reflected light from mirrors to communicate by code between watchtowers. Ship captains used both mirrors and lanterns to communicate with their fleets and army generals frequently used shields to signal troop movements. In the sixth century BC, legend has it that Aeschylus (Figure 1.1) (the 'Father of Tragedy', who apparently met his death when an eagle mistook his bald head for a rock and dropped a tortoise on it!) used a long chain of bonfires from Asia Minor to Argos to pass on the news of Troy's downfall.

Figure 1.1 Aeschylus (525-456 BC) In the second century BC, Polybius (a Greek historian, born in Megalopolis) developed a two digit, five level code by which the whole of the Greek alphabet could be transmitted. It is perhaps interesting to note that it is this last method that is generally recognized as being the first example of optoelectronic signalling. The Chinese, when threatened by the Tartars, lit signal fires along the boarders of their empire, increasing brightness by artificial means to penetrate fog and rain. Genghis Khan (1115-1227) (Figure 1.2) controlled and checked his horsemen by flag telegraphy. During the next few decades, a number of experiments were carried out utilizing various other visual methods. For example, in 1633 the Marquis of Worcester developed long distance communication systems using black and white signs, and in the papers of John Norris of Hughenden Manor in Buckinghamshire there is an enigmatic comment: '3 June 1778. Did this day heliograph intelligence from Dr Franklin in

The history of fiber optics 3

Figure 1.2 Genghis Khan (1167-1227)

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Paris to Wycombe.' In 1781, Norris also built a 30m tower on a hill at Camberley, Surrey, from the top of which he used to signal and place bets by heliograph with Lord le Despencer at West Wycombe. Turning the pages of history once again, it was in 1795 that the Reverend Lord George Murray (the fourth son of the Duke of Athol) was commissioned to supervise the installation of a chain of shutter stations stretching from Plymouth to London (Figure 1.3).

Figure 1.3 Admiralty shutter telegraph relay station sites ( i courtesy of the Royal Corps of Signals Museum, Blandford)

4 Optoelectronics and Fiber Optic Technology

Figure 1.4 The Admiralty shutter telegraph system (artist's impression of a relay station, J. courtesy of the Royal Corps of Signals Museum, Blandford)

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These stations formed the Admiralty shutter telegraph system (Figure 1.4) and consisted of a wood frame 20 feet high by 12 feet wide, containing 3 foot square shutters arranged two by two vertically, which pivoted about their horizontal axis and were operated from the building beneath by ropes and pulleys. By careful positioning of the shutters, 63 changes were possible: sufficient to cater for the whole of the alphabet, the ten numerals, as well as a number of selected phrases - for example: 9 all shutters open - station not at work; 9 all shutters shut - station about to work; next station standby to answer. The stations were normally manned by three men (one to operate the shutters, the other two to act as telescope observers or 'glassmen', see Figure 1.5) and it is recorded that an average message passed from London

The history of fiber optics 5

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Figure 1.5 Model of the inside of the Blandford Camp shutter telegraph station ( i courtesy of the Royal Corps of Signals, Blandford)

to Portsmouth in 15 minutes whereas a prearranged signal could be sent between London and Plymouth and acknowledged back in three minutes. Across the channel and a few years before the Admiralty scheme (i.e. 1792), Claude Chapp6 (a French engineer and cleric who converted an old idea into a reality by inventing the 'semaphore visual telegraph') had succeeded in passing a message between Paris and Strasburg (a distance of over 400 km) using movable signal elements. Chapp6's device (the T-type t e l e g r a p h - Figure 1.6) consisted of two side wings mounted at right angles to a main wing that was positioned at the top of a mast. Changing the position of the main wing with respect to the mast and varying the attitude of the side wings to the main wing by 45 degree steps could give 196 different and easily distinguishable signals. These signals were observed from nearby stations using telescopes and then passed on to the next relay station in a similar manner (Figure 1.7). It was far more efficient than hand-carried messages, but by the m i d nineteenth century it had been replaced by the electric telegraph and all that remains today are a few 'telegraph hills' scattered about. But Chapp6's semaphore system was not the only one in existence. Similar systems were being used in Denmark, Norway, Finland and Holland (Curacao) as shown in Figure 1.8.

6 Optoelectronicsand Fiber Optic Technology

Figure 1.6 Chappe's semaphore visual telegraph (courtesy of Telemuseum.se)

Figure 1.7 Telegraph post at Conde in November 1794 (courtesy of Telemuseum.se)

The history of fiber optics 7

One of the systems used in Denmark between 1794 and 1862.

The Norwegian signalling system used on the of the mountain tops Lyderhorn and Ilsfjellet.

Dutch optical telegraph system on the island of Curacao in the early/ mid-nineteenth century.

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Figure 1.8 Examples of some of the other earlier opto-signalling devices (courtesy of Telemuseum.se)

Turn the pages of history once more and it is Napoleon (1760-1821) who, having quickly recognized the importance of optical signalling, established telegraph stations in the countries in which he was campaigning and equipped his armies with optical telegraph equipment (telegraph ambutantes), similar to Col. John Macdonald's anthropological telegraph illustrated in Figure 1.9. In Prussia, General Freiherr von Muffling carried out a number of trials during the period 1819 to 1830 utilizing optical telegraph systems. The success of these studies led to the construction of the first telegraph line between Berlin and Potsdam. During this time various heliograph

8 Optoelectronicsand Fiber Optic Technology

Figure 1.9 Napoleon I (Emperor of France 1769-1821) and CoL John Macdonald's anthropological telegraph ( ,~ courtesy of the Royal Corps of Signals Museum, Blandford)

Figure 1.10 Typical heliograph

The history of fiber optics 9

(Figure 1.10) and signal lamp systems were also developed enabling signalling over distances of around 100 kilometres. The heliograph was primarily used by armies for signalling to a distant point. It comprised a wooden tripod and a mirror assembly, the back of which was covered by a brass plate with a brass stump and pivot that connected to the Morse key via a brass tube. By adjusting the knurled tube and a Morse key the signaller could signal in Morse, by sunlight, to his distant observer. By the 1850s, heliograph systems were widely used by the military (Figure 1.11).

Figure 1.11 Heliograph operators in India (..,~..courtesy of the Royal Corps of Signals, Blandford) The size of the heliograph mirror depended on its intended use. The largest (which was primarily used by headquarters and garrisons) had a mirror 12 inches in diameter, but other standard sizes included the 5-inch mirror for infantry units and the lighter 3-inch instruments for cavalry units. The range of operation depended upon the strength of the sunlight and visibility. Under normal conditions, ranges of 20-30 miles with a 3-inch mirror, 30-40 miles with a 5-inch mirror and 80-90 miles with 12-inch mirror could be expected, but these ranges were frequently exceeded in practice.

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10 Optoelectronics and Fiber Optic Technology

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Heliographs had one unfortunate problem, however, they could only be used on cloudless days! This problem was largely overcome by inventors such as Henry Coxwell who developed balloon signalling. Figure 1.12 represents Coxwell's method of adapting semaphore arms of various shapes and symbols to convey, according to a preconcerted arrangement, any required information to those on the ground.

Figure 1.12 Henry Coxwell's balloon signalling (courtesy of London Illustrated News, 8 October 1879)

In the 1840s, a Swiss physicist (Daniel Collodon) and a French physicist (Jacques Babinet) showed that light could be guided along jets of water for fountain displays. Then in 1850, John Tyndall (Figure 1.13), a schoolteacher, noted that light could be guided inside a clear material, and by using water that flowed from one container to another and a beam of light, he demonstrated that light used internal reflection to follow a specific path. The principle was very simple, as the water flowed from the first container, Tyndall directed a beam of light at the path of water and the light followed a zigzag path inside the curved path of water. This simple experiment marked the first research into the guided transmission of light. But it was not until the 1880s that Alexander Graham Bell (in conjunction with Sununer Tainter) patented an optical telephone system, which he called the photophone, and successfully modulated a beam of sunlight using a diaphragm mirror. This is generally recognized as the

The history of fiber optics 11

Figure 1.13 John Tyndall, British scientist (1830-1893)

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first mobile phone! The action of the photophone is very simple (Figure 1.14a). Rays of sunlight (or a powerful light source) are reflected by a flat mirror (h) into a system of lenses (a and b) that form a beam of light on to a silver-coated glass plate (H). A person speaking into the mouthpiece of the transmitter (see Figure 1.14b) causes the silver-coated plate to vibrate which in turn causes the reflecting surface of the plate to change shape. This affects the strength of the light rays, which are compressed by a second set of lenses (c), and then reflected to the receiver. At the distinct end (see Figure 1.14c), the light rays are received by a silver-coated copper parabolic reflecting mirror (P). By using a sensitive selenium-photoresistor (S) (comprising a cylinder of copper plates, separated by strips of mica and filled with s e l e n i u m - whose resistance varies according to the quantity of light that strikes it), connected to a battery and a telephone instrument (t), the system is able to reproduce the speaker's voice. On a good day, when the weather was sunny, the photophone had an effective range of over 200 m, but it did not work at night or when the weather was cloudy. The transmission distance was increased to 2 km when Bell incorporated the use of an electric globe following Edison's invention of the light bulb, but the user still had to carry a fairly cumbersome piece of equipment around, with two such devices being needed for two-way communication. Alexander Graham Bell's earlier invention, the telephone, proved to be a far more practical proposition, therefore, and although he dreamed of sending signals through the air, he found that the atmosphere didn't transmit light nearly as reliably as wires could carry electricity.

12 Optoelectronics and Fiber Optic Technology

Key h

Flat mirror

Very thin mirror

b

Lens

Parabolic reflector

Allun cell lens to cut off heat rays

Selenium photoresistor

c

Compression lens

Figure 1.14

t

Alexander Graham Bell's photophone

Telephone earpiece

The history of fiber optics 13 Table 1.1

Patent number 235,199

Details of the photophone's US patent registration Type Inventor

U

Bell

Appfied

G r a n t e d Claims P a g e s

08/28/1880

12/07/1880

18

13

09/25/1880

12/14/1880

3

3

Alexander Graham

235,496

U

Bell

Alexander Graham and Tainter, Sununer

Description

Apparatus for Signalling and Communicating, Called 'Photophone'

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PhotophoneTransmitter

All of these methods were of course affected by the visual transparency of the medium through which they were being propagated (i.e. air), and fog, rain, storms, cloud and snow were some of the problems to be contended with. Another major problem that affected these early lightwave communication systems was the inability of lightwaves to go around corners, and avoid trees, buildings and mountains. The transmission path, therefore, had to be an unobstructed line of sight between transmitter and receiver. In the same period, William Wheeler invented a system of light pipes which were lined with a highly reflective coating, and by using light from an electric arc lamp placed in the cellar, he was able to illuminate almost the whole of the house by directing the light around the home via the pipes. Later on in 1888, the medical team of Roth and Reuss of Vienna used bent glass rods to illuminate body cavities and in 1895, the French engineer Henry Saint-Rene designed a system of bent glass rods for guiding light i m a g e s - in an attempt at early television. In 1898, American David Smith applied for a patent on a bent glass rod device to be used as a surgical lamp. By the turn of the century, however, several inventors had realized that bent quartz rods could carry light, and had patented them as dental illuminators, and many doctors were using illuminated plexiglass tongue depressors. But whilst all this was happening, a new technology was slowly developing that would eventually overcome the problem of optical transmission. This technology depended on a phenomenon called 'total internal reflection', which could confine light in a material that was

14 Optoelectronicsand Fiber Optic Technology

Figure 1.15 John Logie Baird (1888-1946)

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surrounded by another material with a lower refractive index, for example glass in air. During the 1920s, the famous English inventor John Logie Baird (Figure 1.15) (remembered as being an inventor of mechanical television - an earlier version of today's television- and inventions related to radar and fiber optics) and an American (called Clarence Hansell) patented the idea of using bundles of hollow pipes or transparent rods to transmit images for television a n d / o r facsimile systems. In Munich during the 1930s a German medical student (Heinrich Lamm), whilst trying to find a way of looking at inaccessible parts of the human body, successfully demonstrated, with the aid of a 'light-stick', that by shining a light bulb filament on to an image, that image could be transmitted through a short bundle of optical fibers. However, the image transmitted by the unclad fibers was very poor and his effort to file a patent was denied because of Baird's previous British patent. Later on (i.e. in 1951), Holger Hansen also applied for a Danish patent for fiber optic imaging but was turned down by the Danish patent office because of existing Baird and Hansell patents. Hansen tried to interest some companies in his invention but without success. Historically, nothing else appears to have happened concerning the use of fiber bundles until 1954, when a Dutch scientist (Abraham van Heel) from the Technical University of Delft produced a paper concerning imaging bundles in the popular British journal, Nature. He had

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proved that instead of using 'bare' fibers with total internal reflection at the glass-air interface, if the bare fiber (glass or plastic) was covered with a transparent cladding of lower refractive index, the reflective surface would be protected from contamination, and 'crosstalk' (i.e. the leakage of signal from one fiber to another) was greatly reduced between them. Figure 1.16 above shows the difference of a ray of light entering at a small angle (1) compared with another ray that enters at a different angle (2). The result is that different rays (or modes) of light will reach the end of the fiber at different times, even though the original light source was the same. Van Heel's experiments eventually led to the development of glass-clad fibers with an attenuation of less than one decibel per metre, which, whilst it was all right for medical imaging, was much too high for the telecommunications industry. Indeed, with an exponential growth rate in telephone traffic, television and the perceived use of videotelephony even in those days, telecommunications engineers were already asking for more transmission bandwidth. The use of higher optical frequencies seemed the best possible solution and with the invention of the laser (light amplification by stimulated emission~radiation) in 1960 came the announcement in the July 22 issue of Electronics that 'Usable communications channels in the electromagnetic spectrum may be extended by development of an experimental optical-frequency amplifier.' With the emergence of the continuous wave helium-neon laser this announcement quickly became a reality. By 1965, however, there were still technical barriers to the use of lasers, and optical waveguides were also proving to be a problem. This was mainly because, although optical fibers were very similar to the plastic dielectric waveguides that were used in certain microwave applications, the core of the drawn fibers was so small that they carried light in only one waveguide mode. Another problem was that most of the telecommunications industry had already discarded the use of fibers as being too lossy! So whilst attenuation of a decibel per metre was all

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16 Optoelectronicsand Fiber Optic Technology

Figure 1.17

Charles Kao

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right for medical purposes (e.g. for looking inside the body), telecommunications, which had a requirement for operating over long distances, could only accept a maximum loss of 10 or 20 decibels per kilometre. Help was around the corner, however, as a team from Standard Telecommunications Laboratories (STL) headed by a young Shanghai engineer called Charles K. Kao (Figure 1.17) and another young STL engineer who specialized in antenna theory, called George Hockham, were trying to find a way around fiber attenuation. With samples collected from a whole host of fiber manufacturers, they gradually built up a database of their (i.e. fiber's) properties, which enabled them to reach the conclusion that most of the high losses in early fibers were due to impurities and not to the silica glass itself! They were convinced that with careful manufacturing, these fiber losses could be reduced below 20 decibels per kilometre. Together Kao and Hockham presented a paper at a London meeting of the Institution of Electrical Engineers containing a proposal for longdistance communications over single-mode fibers. This was reported in the 1 April, 1966 issue of Laser Focus as follows:

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Dr C. K. Kao observed that short-distance runs have shown that the experimental optical waveguide developed by Standard Telecommunications Laboratories (STL) has an information-carrying capacity of one gigacycle, or equivalent to about 200 TV channels or more than 200 000 telephone channels. He described STUs device as

The history of fiber optics 17

consisting of a glass core about three or four microns in diameter, clad with a coaxial layer of another glass having a refractive index about one percent smaller than that of the core. Total diameter of the waveguide is between 300 and 400 microns. Surface optical waves are propagated along the interface between the two types of glass. According to Dr Kao, the fiber is relatively strong and can be easily supported. Also, the guidance surface is protected from external influences and the waveguide has a mechanical bending radius low enough to make the fiber almost completely flexible. Despite the fact that the best readily available low-loss material has a loss of about 1000 dB/km, STL believes that materials having losses of only tens of decibels per kilometre will eventually be developed. Based on Kao and Hockham's presentation, the British Post Office set up a new research fund of s million pounds to study ways to decrease fiber loss and in a similar manner, many institutes and laboratories from around the world were also actively investigating ways of trying to reduce fiber loss. Most of this research centred on an attempt to purify the glass used for optical fibers but at the Corning Glass Works, three researchers (Robert Maurer, Donald Keck and Peter Schultz, Figure 1.18) were experimenting

Figure 1.18 The original three Coming researchers

with fused silica, a material that could be made extremely pure, but which had a high melting point and a low refractive index. By carefully adding controlled levels of dopants, the Corning researchers managed to increase the refractive index of the core slightly above that of the cladding, but without raising the attenuation dramatically. The Corning researchers' experiments came to fruition in September 1970 when they announced that they had made a single-mode fiber with

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18 Optoelectronics and Fiber Optic Technology

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an attenuation of below 20 d B / k m in a 633-nanometer h e l i u m - n e o n line. This breakthrough is generally recognized as the start of fiber-optic communications and opened the door to the commercialization of fiber optics, first for long-distance telephone service and later for computerrelated telecommunications (such as the Internet) and even medical devices (like the modern endoscope). This fiber optic wire or 'optical waveguide fiber' was patented by Corning (patent number 3,711,262) and was capable of carrying 65000 times more information than copper wire, via a pattern of light waves which could be decoded at a destination even a thousand miles away. The team had solved the problems presented by Dr Kao and it is now an accepted fact that fiber optic communications is one of the 10 most outstanding engineering achievements of the last 25 years. It is extremely doubtful (certainly not in my lifetime!) whether a superior method for long-distance information transfer will be discovered in the near future. In the same year that Corning patented the optical waveguide fibre (i.e. 1970), Bell Labs in America and a team from the Loffe Physical Institute in St Petersburg manufactured semiconductor diode lasers capable of emitting a continuous wave at room temperature. With the emergence of better manufacturing practices and the use of longer wavelengths, fibers were gradually being produced with even lower attenuation and in 1976 telephone field trials were conducted by AT&T using these types of fibers to transmit light (at 850 nanometers) with the aid of gallium aluminium arsenide laser diodes, for several k i l o m e t r e s - without repeaters. By then losses of less than 2 d B / k m were the accepted norm, but this was rapidly reduced to about 0 . 5 d B / k m when the new lnGaAsP lasers working in the 1300 nanometer range were introduced. So, although the possibility of using a dielectric rod as a waveguide had been studied during the late 1800s and a paper had actually been written about it in the 1920s, it was not until 1966 that Charles Kao and George Hockham patented the principle of 'information transmission through a transparent dielectric m e d i u m ' (i.e. glass fiber), that the use of glass fibers actually became a viable proposition. Since the development of optical fibers, more and more communication systems are now using fibers to pass optical signals over long distances with very little loss (compared to the losses experienced by electrical signals over copper lines). Following the development of laser diodes, the use of optoelectronics has now become the preferred method for cable communication. Indeed, a single glass fiber the thickness of a h u m a n hair (see Figure 1.19) can carry the equivalent of 300 million simultaneous telephone calls - roughly all the phone calls going on in America at any one time.

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1.2 Basic principles of optical line transmission

Some crystals, for example gallium arsenide (GaAs), emit light at a wavelength very close to visible light when an electric current is passed through them. Figure 1.20 shows the frequency and wavelength of rays and light making up the electromagnetic spectrum. As can be seen from Figure 1.20, visible light (with wavelengths in the 400 nm to 750 nm range) is only a small part of the light spectrum. Above this is the near infrared region (i.e. 750 nm to 1600 nm) which fiber optic transmission u s e s - primarily because the fiber propagates the light much more efficiently at these wavelengths. This light emission is produced by the release of energy (photons) from the atoms of a material and is caused when the atoms are excited by heat, chemical reaction or some other means. Today's low-loss glass fiber optic cable can offer almost unlimited bandwidth and has many advantages over previous transmission media. In a fiber optic system, the sound waves are converted to electrical signals, which are coded as a series of pulses fed as a rapid burst of laser light through the fiber optic cable. At the other end they are received, decoded and converted back to sound waves. A lightwave system (Figure 1.21), therefore, is composed of four basic parts: a transmitter, fiber optic cable, regenerator and a receiver. The transmitter is the light source, which can be a light emitting diode (LED) or a laser. This source is modulated (i.e. turned on or off in a digital system) to represent the binary digits (ls and 0s) it receives from an electrical transmission system. The transmitter then converts the electrical analog or digital signal into a corresponding optical signal.

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Also contained in the laser module is a drive circuit, which is used to regenerate the amplitude of the signal and supply the modulation current for the laser diode. Biasing, to permit the light pulse rise-time being delayed with respect to the drive current pulse is also normal. Regulation of the modulation depth and optical power is achieved with control loops and an alarm circuit is incorporated to ensure the laser diode is not overloaded. The receiver, on the other hand, normally uses an avalanche photodiode to convert the received optical signal into an electrical signal. The current pulses of the photodiode are converted into voltage pulses by a gain-controlled preamplifier called a transimpedance amplifier. This is followed by a dual-gated field effect transistor (FET) amplifier. A lowpass filter provides band limiting. Such an optical receiver is shown in block diagram form in Figure 9.10.

Figure 9.10

Functional diagram of an optical receiver

It is not uncommon to find PIN photodiode, FET and bipolar transistors integrated on a ceramic substrate. Normally, germanium avalanche photodiodes are used for wavelengths between 840 to 880 nm, while PIN photodiode with GaAs FETs are usually used for 1300 nm. 9.7.3 Fiberless transmission

Using fiber optics for communications purposes has many advantages particularly with regard to their enormous data carrying capacity. LANs can be made virtually futureproof by maximizing available bandwidth whilst at ttie same time leaving the majority of the existing infrastructure unchanged. This is all right, of course, provided that you already have fiber optic cable running throughout your building. Having to install an optical network based on an anticipated growth rate could well prove too expensive for many businesses.

Future developments 249

During 2000, Bell Lab demonstrated an optical system called OpticAir that uses similar technology to that found in a normal fiber network except that it transmits the photons through the open air. According to Kathy Zheleg, Vice President of Marketing for Lucent's optical networking group, only 5 per cent of the buildings in the USA have a fiber network installed. Just as the main m e m o r y requirements of a PC are forever increasing, the amount of data passed around the network is unlikely to drop and the need for additional b a n d w i d t h will always be there. OpticAir employs the same lasers as used in a fiber link, based around 1550nm, but uses special optics to reduce the power density. Lucent Technologies claims this gives a line of sight, point-to-point communication link that can reach twice visibility. 'If you can see for a mile, you should get a reliable link over two miles.' Their experts tell us the system uses state-of-the-art lasers, amplifiers and receivers that can be placed on rooftops or in office windows to transmit voice, data or video traffic from point to point through the air. It makes use of DWDM technology to increase network capacity in metropolitan areas and campus environments where cost, geography or other constraints may make fiber connections impractical. While there are no requirements for a licence to operate an optical communications link in the open air, there are rules against firing a laser across a city. To comply with UK and US laws, the power density is downgraded to less than 100 m W / c m 2 using a diffusion lens on the output of the transmitter, to split the beam into two as it leaves. This is in contrast with the traditional fiber beam former, which concentrates the laser w i n d o w energy to maximize the distance between repeaters. The divergent beam and lower power means if someone inadvertently peers into the transmitter they should not be blinded. Because this system is designed for short-range transmission, the reduced power density does not present a problem. Potential applications for the OpticAir system include transmitting data between high-rise office buildings, enabling naval ships to share huge amounts of information while in port and establishing temporary, high capacity data links for special events.

9.7.4 Optical Ether The concept of an 'Optical Ether' that exploits the b a n d w i d t h of fiber in a similar manner to the radio spectrum has been demonstrated in the laboratory with a number of terminals capable of switching 100 G b i t / s capacities. Related studies have shown that this approach could be extended to the replacement of the central office for up to 200 000 lines with a 100 per cent non-blocking capability and with a potential for

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improving them to four million lines. At today's service levels and with a similar level of call/service blocking, up to 20 million lines could then be accommodated, with a potential for significantly more. Beyond this level the need for conventional switching of some kind becomes necessary again. The key problems and limitations now hinge on the availability of sufficiently miniature and reliable electro-optics, memory capacity, control systems and wavelength standards. Commercialization is not anticipated before 2010.

9.7.5 Optical radio Another interesting prospect for transparent networks concerns customer mobility. As it is possible to transport raw microwave signals over fiber with only a single stage of frequency translation at each end, a radio cell can therefore be replicated over several remote and diverse locations to give the illusion of a single location. Effectively six dispersed company locations would, therefore, appear as one to the individual user. The certainty of this prospect increases with the realization that optical wireless is also being developed for in-building and street use for both telephony and broadband services.

9.8 Industry The increased use of microelectronics in industrial controls has resulted in extremely high signalling rates being present in the system. The problem, of course, with high signalling rates is the requirement for low signalling voltages and this is one of the main reasons why industry is turning to optical fibers and a few of these applications are described below.

9.8.1 Leak detection Whiteman Controls Corporation of America has designed and installed a leak detection method for double-walled piping systems containing hazardous fluids. The theory behind this is very simple but extremely effective and consists of a number of minute pressure sensors, which are placed at regular intervals along the pipe. The sensors are joined to an electro-optical connector and the light is passed via the optical fiber cable to an optoelectronic interface located some 2 to 3 km away from the hazardous area.

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9.8.2 Optical fiber drill bit temperature monitor

An optical fiber drill bit temperature monitor has been designed by Vanzetti Systems for use with printed circuit board laminate drill bits. An optical fiber infrared detector head, connected to an optical fiber cable looks directly at, and measures the temperature of, the drill bit. The infrared head is capable of detecting overheating of drill bits (due to dulling or overuse), and details are then passed, as a signal, to an alarm circuit via the fiber cable.

9.8.3 Optical fiber soldering iron Although still very much at the drawing board stage, the development of an optical fiber soldering iron that can be used for field maintenance as well as in the laboratory is well advanced.

9.8.4 Optical computing The fastest computer in the world used to be (probably still is?) the BBC Andromeda, but even this has to rely on step processing or sequential functions which severely restricts its capability. Light can emit hundreds of modes in parallel without interference and, in the late 1990s, American SDI research investigated the possibility of an optical switch. This was effectively the first step towards optical computing which can be achieved by optically multiplexing many signals together and then switching one or any number of information channels in parallel. As described by David Larner in New Electronics, August 1999, mainstream optical components generally fall into two groups, those that emit light and those that detect light. There is a third group of optical components, h o w e v e r - those that direct light. Since the discovery of nonlinear crystals, which have the ability to change their refractive index when an electric field is applied, scientists have dreamed of building the optical computer. An advanced research initiative has set a 10-year design window for achieving a petaflops supercomputer, a system 1000 times faster than today's leading edge, teraflops supercomputing technology based on hybrid technology multi-threading. The central processor will be built with low temperature superconducting circuits. High speed RAMs will use CMOS chips cooled by liquid nitrogen. System interconnect will be optical, rather than electronic, three-dimensional holographic crystals will enable fast, high volume storage. In addition, the heterogeneous hardware will be tied together with an innovative software system blending such concepts as threaded execution, data flow processing and object oriented programming.

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For the time being, optical computers will have to remain a fascination because the functional elements, such as flip-flops, gates and latches take up far more space than the equivalent electronic devices. Second, because the means of switching optical signals around often relies on micro-machined mirrors, they have a mass which limits the switching speed.

9.8.5 Optical multiplexers It is strange, but true, that the material used to make an optical fiber is silica (Si) whilst the material used as the insulator in the manufacture of integrated circuits is silicon dioxide (SiO2)! This fact has not gone unnoticed by researchers around the world and the possibility of building optical multiplexers using semiconductor production techniques is currently being investigated.

9.8.60pto-isolators Opto-isolators provide a low-cost, space-efficient, easy-to-use solution to high voltage isolation requirements. With careful printed circuit board (PCB) design, the input circuit can be electrically isolated from the output stage for up to 7500 volts peak differential.

9.8.70ptoelectronic switches Optoelectronic switches operate on the principle that objects opaque to infrared will interrupt the transmission of light between an infrared emitting diode and a photosensor. Similarly, photoreflective switches operate by detecting light transmitted from an infrared emitting diode with a photosensor positioned to sense a reflective object positioned at a point of optimum response. Optical switches provide non-contact sensing of linear or rotary motion, and have many different individual applications such as in printers, photocopiers, weighing, measuring, automotive and entertainment equipment. Unlike conventional mechanical solutions, optoelectronic switches are not subject to wear or corrosion and they can interface directly to, and with, electronic control circuitry.

9.8.8 High speed optical switches Researchers at Glasgow University have demonstrated a high speed optical switch based on a semiconductor waveguide. The Scottish researchers claim the aluminium gallium arsenide waveguide can carry light pulses of less than ten picoseconds in duration and could lead the

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way to optical telephone systems capable of handling 1.2 million simultaneous telephone calls. On the other side of 'The Pond', scientists at Bell Labs have built a microscopic optical switch that works like a child's seesaw and demonstrates the first practical optical switching technology using micro electromechanical systems (MEMS). The seesaw in the experimental switch is a tiny, pivoting bar with a gold-plated mirror on one end. The mirrored end fits in a space about one-tenth as wide as a human hair, between two optical fibers. In the rest position (i.e. when the switch is off) the mirror rests below the cores of the two fibers, allowing light to travel from one to the other. To turn the switch on, a voltage is applied at the other end of the pivoting bar which generates an electrostatic force sufficient to lift the mirror, reflecting the light away from the fiber cores. MEMS devices are built in much the same way as integrated circuits with various films, such as polysilicon, silicon nitride, silicon dioxide and gold, deposited and patterned to produce multiplayer, three-dimensional structures. The major difference is a release step at the end of fabrication.

9.9 Military In the early 1960s, optical fiber technology, along with semiconductor and laser technology, became a particularly attractive possibility for strategic and tactical military applications. The military has always been concerned with radiation of energy from the transmission media and the susceptibility of communication systems to high energy electromagnetic radiation especially from nuclear weapons. Unfortunately, cost and doubtful performance factors have limited large-scale military implementation. With the emergence of more cost-effective manufacturing techniques, together with increased reliability, the military is now actively upgrading existing copper systems with optical fiber cables and extending digital ISDNs and LANs for fixed installations. In keeping with this general trend, the American forces are now replacing a microwave system with a single-mode optical fiber backbone transmission cable in the Republic of Korea. 9.9.1 Laser dazzler

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in their May 1998 edition that the US Defence Advanced Research Projects Agency (DARPA) and the National Institute of Justice (NIJ) had developed advanced technology (which they are now seeking to commercialize) into the 'laser dazzler', a device that could be widely used by the military enforcement communities as a nonlethal weapon.

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The technology is being incorporated into a 250 milliwatt 532nm greenlaser hand-held flashlight. The laser dazzler device includes a miniature laser and power supply and has output optics that can temporarily expand the eye-safe laser into a blinding light. It can also penetrate smoke and fog at more than twice the distance of white light. DARPA and the NIJ believe the market for the technology will include military security personnel, law enforcement, border control, crowd control and underwater surveillance.

9.9.2 Plastic opto-chips Currently, most fiber optic networks employ WDM technology. Each system accommodates large numbers of optical wavelengths, each of which is modulated and carrying data. To place even more optical data modulated wavelengths that are on a fiber will require devices such as an opto-chip to allow modulation of each wavelength component at a much wider bandwidth and with lower signal power. As reported by AFCEA (signal Jul 2000), a new polymer-based electrooptic modulator (that serves as the interface for placing electronic data on to an optical carrier for transmission across a fiber optic network) could also be used to increase the bandwidth of fiber optic networks and clear the way for applications ranging from broadband |nternet access to fullscale holographic projection currently found in science fiction television programmes! Developed in a joint research effort by scientists at the University of Southern California, Los Angeles, and the University of Washington, Settle, this new technology also uses less power than present-generation modulators and features low noise disturbance. The universities have now succeeded in integrating polymeric materials with semiconductors. This has been achieved in both horizontal and vertical integration, where polymeric electro-optic circuits have been produced on top of very-large-scale chips. The fabrication process involves placing a layer of planarizing polymer with an optical-quality surface on top of a chip. Reactive ion etching techniques handle deep interconnections. The same etching technology can be teamed with shadow ion etching or grey scale etching to build three-dimensional, vertically integrated passive/active optical circuits which will allow an optical waveguide to be constructed that vertically links different chip layers. The competing technology for these polymer devices currently is lithium niobate, a crystalline technology that has been used for several decades. Lithium niobate modulators are limited to a speed of between 10 and 20 gigabits per second, however, and each requires an operating voltage of between 4 and 5 volts. The current polymer modulators have a drive requirement of less than 1 volt and can operate from 40 to 80

Future developments 255

gigabits per second. This lower power consumption also results in reduced heat. Whilst it is not anticipated that these polymer devices will replace all lithium niobate systems - especially those in standard, single modulator device a p p l i c a t i o n s - preliminary tests have indicated that a single modulator measuring about 1 micron can provide more than 300 gigahertz of bandwidth, enough to carry all of a major military unit's telecommunications, computer, television and satellite traffic. The new modulator technology is not bound to its current polymer make-up, however. Chemists are actively pursuing development of even better materials. From a military perspective, near-term benefits could be realized in systems such as large communications networks, radar and electronic countermeasures, electrically-steered antennas and radar transmitters as well as optical gyroscopes in airborne guidance systems. In the commercial sector, both satellite and fiber optic telecommunications could be prime beneficiaries and the first commercial customers of these modulators would likely be firms that operate fiber optic systems, such as the regional and international telecommunications companies. The long-term view is that the technology has the potential to open up many new applications, similar to those that emerged from the development of silicon semiconductors some 30 years ago. The next step for the researchers is to move these modulators from the laboratory into the commercial marketplace. Commercializing the technology will require significant long-term testing, for temperature and photostability and funding (!) - but this work is underway.

9.9.3 Fiber optic gyroscope The fiber optic gyroscope (Figure 9.11) consists of a long length of fiber w o u n d into a coil. Laser light is sent into both ends of the fiber using a beam splitter, which reflects 50 per cent of the light and transmits the remaining 50 cent. Light travelling clockwise round the coil emerges from the end of the fiber with the same phase as the light travelling in the

Figure 9.11 Fiber optic gyroscope

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anticlockwise direction. This is because both have travelled exactly the same distance. If the gyroscope is now rotated, say, in the clockwise direction, then the light travelling round the fiber coil in the clockwise direction will take longer to reach the end of the fiber because the end is always moving away from the light. In a similar manner, light travelling in the anticlockwise direction will take less time to reach the other end because that end is moving towards the light. This introduces a phase difference between the two emerging beams of light, which is proportional to the rate of rotation of the gyroscope.

9.10 Local government Within local government, fiber optic cables and optoelectronic systems are now becoming commonplace, as shown in the following examples.

9.10.1 Optical sensors Military researchers have long dominated 'smart structure' work, with most of their efforts devoted to embedding fiber sensors in composite materials used in aircraft. Now the car industry is looking at optical sensors to monitor and control tomorrow's family car. At Liverpool University, a group of scientists is currently testing a new approach to sensing temperature, pressure, linear and rotational movement, voltage and current. The project concerns fiber sensors that measure the change in colour of light (i.e. chromatic modulation) as it passes through, or is reflected by, a suitable modulator such as glass. Conventional electronic sensors can provide some data, but they make only point measurements. Fiber sensors, including multimode sensors (based on mode-distribution statistics and single-mode polarization sensors), on the other hand, can evaluate stresses throughout structural elements. In construction projects, optical sensors are now being used to measure stress during construction. This is extremely important, because buildings typically experience their heaviest structural loading prior to completion. Goals include evaluating stresses during construction, monitoring vibrations in the building once it is completed and observing how well the fiber sensors survive construction.

9.10.2 Office lighting As well as being used for communications systems and data transfer, fiber optics have also been used for decoration and in mainstream lighting. Indeed, it is anticipated that increased energy costs will drive the need for more energy efficient fiber optic systems.

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For example, in Australia in a temperate climate, air conditioning is calculated on the basis that 70 per cent of total building energy for air conditioning, and 50 per cent of the air conditioning load is used to combat the lighting system! As fiber optics do not generate any heat into the air-conditioned load area, this provides a potential energy saving of 35 per cent of the total building energy load. The office of the future will be dramatically different. Once all offices were illuminated with levels of illumination around 400-800 lux depending on the country, and this illumination was on the total horizontal and vertical surfaces. This was driven by the types of tasks one carried out in the office, wide desk and table top areas for the pyramids of paper spread all around. But the new computerized office is radically different and the screen and the keyboard dominate office tasks. As the screen is already illuminated only the keyboard and local task areas in a booth will require localized light, light that has no electricity, no radiation and no h e a t - fiber optic light. The surrounding areas to contrast correctly will have low levels of 100-150 lux for simple movement within the area.

9.10.3 Decorations Instead of using hundreds of tiny bulbs to simulate the firework display over the Euro Disney castle during the millennium celebrations in London, the effect was achieved from 400 fibers transmitting light from one 150 W metal halide light source. A multi-colour wheel in the optics created a kaleidoscope of intense moving colours, bringing the tableau dramatically to life. The entire display consisted of ten 60 ft wide, 22 ft high double-sided garlands, suspended across Regent Street. All were additionally highlighted with 500 W tungsten halogen haline floodlights to uplight the characters from their mounting positions at the base of each tableau display.

9.10.4 Fiber optic road signs A range of designs such as speed-activated 'slow down' signs, 'overheight' warnings for installation at low bridges and messages such as 'queue ahead', 'flooding' and 'overweight vehicle' are increasingly used on today's highways. The fiber optic sign houses tungstenhalogen lamps that transmit light through glass filaments, the legend being formed by their intensely illuminated terminals. Normally blank, the 'secret' sign is either switched on manually or automatically activated by a triggering mechanism, such as a speed or infrared detector.

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The latest Department of Transport (DOT) specification requires that the illuminated message shall be continuously dimmed over the full range of ambient light, by means of an electronic 'contrast control' device, rather than a single light/dark setting previously allowed. This is normally achieved by incorporating two photocells in the sign head, which automatically adjust the luminous intensity across the complete brightness scale, reacting from brilliant sunlight (40000 lux) down to virtual total darkness (40 lux). The new specification also stipulates that the design should provide for full remote monitoring of all sign functions, safeguarding against lamp failure a n d / o r displaying the message at an inappropriate time. Equipment must also incorporate provision for manual switching and electrical interlocking to prohibit the simultaneous display of two legends, as well as a thermostat-controlled anti-condensation heater, to prevent the clear polycarbonate face misting up in low ambient temperatures.

9.11 Medicine In medicine, recent growth in the use of optics technology for biomedical research and health care has been explosive. Using fiber optics in medical procedures allows things like magnetic resonance imaging (MRI) and position emission tomography (PET) images to be transmitted to anyone, anywhere. Using fiber optic equipment during surgery also means using less invasive procedures, which in turn reduces recovery time, is less traumatic on the body and costs less for the procedure. 9.11.1

Lasers

- medical

uses

Lasers have been expanding into the medical arena and improving clinical results since the mid-1960s. These intense beams of light are used to photocoagulate, cut a n d / o r vaporize tissue and, in many types of surgery, have replaced the scalpel. It is estimated that approximately 5 per cent of the half-million doctors who are candidates to use the laser, employ it actively and this number is expected to grow to 25 per cent over the next five years. From brain surgery to kidney stones, eye surgery, gall bladder operations, oral surgery and irradiating cancer cells, the laser is redefining surgical procedures. It has become a tool the surgeon must master and use, not just to improve his own techniques but because his patients are increasingly asking for it. Medical lasers deliver either pulsed or continuous wave beams to tissue. When the beam is absorbed by tissue, localized heating occurs, which produces the desired surgical effect. As tissue temperatures rise,

Future developments 259

the tissue blanches white as it coagulates, shrivels as it desiccates and turns to steam and vapour as it vaporizes. The wavelength of the laser and the spectral absorption characteristics of the tissue determine how effectively the heat of the beam is transferred to the tissue. The three primary surgical LASERs used today are the carbon dioxide laser, emitting at 10.6 ]am, the Nd:YAG laser, emitting at 1.06 ]Jm and the misnamed argon/KTP laser (actually lasers), emitting in the green at 488, 514 and 532 nm. Recently, interest in the excimer lasers has been renewed for ophthalmology and two new solid-state l a s e r s - Ho:YAG and er:YAG - are being made available for specialized surgery. 9.11.2 Flexible fiber optic curvature sensors

Measurement sensors mounted on tape or attached to small subassemblies are frequently used to measure angular positions or movements on humans or machines. They are capable of detecting every movement and produce an output voltage that is proportional to the curvature or displacement of the sensor. A typical measurement sensor will respond to any curvature as a form of interference with the linear, bipolar modulation of light that is being transmitted through specially treated fiber optic loops and they will produce a linear, stable, high level output voltage in response to the bending or displacement of the sensor and where the output can be used to form real time computer images and data collection corresponding to complex shapes. Measurement sensors can be used to measure the angle of any small movement but they need to be robust enough to withstand millions of bends and at the same time possess attributes such as low cost, inherent safety, high speed and great flexibility. Applications include biometrics, CAD input, virtual reality (VR), crash testing, medical visualization and deformation studies.

9.12 Other possibilities The opportunities of photonics worldwide are immense and the global photonics industry is expected to be worth around s billion by 2010. Some 6000 new photonics R&D and manufacturing jobs have recently been announced in the UK, including major UK expansion plans by a number of multinationals. One immediate application for lasers in bringing optical communications to the desktop will be in distributing data around office buildings. lasers will be used in the risers, which take data around the buildings, but the drop to the desk will be handled by LEDs over multimode fiber.

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260

Optoelectronicsand Fiber Optic Technology

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Bringing fiber to the home is a more difficult task than bringing fiber to the office, however. The problem is more economical than technical and as soon as homes start to be wired for this new technique, the market will open up. If users want broadcast quality video, there will be the need for more sophisticated technology. As far as fiber to the home is concerned, cost is seen as one of the main barriers. The major cost is installing the fiber itself and this dominates the cost of components.

9.12.1 Internet It is a recognized fact that the speed of components used by telecommunications networks doubles roughly every 18 months, and the cost per bit of data they transmit halves. Compared to telecommunications, the use of the Internet doubles every 100 days! The use of optoelectronics and fiber cables to provide a backbone for this ever-increasing need for speed and connectivity is now widely accepted and with its virtually limitless bandwidth, single fibers can carry thousands upon thousands of simultaneous transmissions. Indeed, Time Warner Telecom in the US has recently asked industry to provide a North American fiber optic telecommunications network that will be fast enough to allow everyone in the US and Canada to simultaneously send a one page e-mail across the n e t w o r k - assuming, that is, that they ever wanted to!

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9.12.2 Cars and planes Today's cars have bulky lighting systems. With fiber optic cable being small enough to manoeuvre around, car designers can be given more freedom to design their vehicles. Optical systems used in cars can also control things like stereo, heat and airconditioners. In airlines, fiber optic cable is light, so there is no need for heavier cables to be used on board and this enables load savings. With the use of fiber optics, airplanes can have internal communication systems which are not exposed to outside elements and pilots will be able to see damage to certain parts of the plane without having to wait to land.

9.12.3 Optical processing and computing The use of optical technology in storage and signal processing is n o w becoming commonplace in certain application areas and the increased availability of optical hard disks for personal computers and domestic CD players is phenomenal. The impact of optical processing on telecommunications has not been so dramatic but it is anticipated that optical processing will provide a major input to neural network

Future developments 261

development. Many research-level neural networks are being produced with optical components. The main reason for this is the ability of optics to offer massive parallelism and interconnections. Since these parameters are fundamental to the principles of neural computing, optics is clearly suitable, so much so that the technologies are likely to develop very closely.

9.12.4 Mining Modern underground or open-cast mines use fiber optic transmission systems to monitor and control (from the surface) safety systems, fire and gas alarms, water, compressed air and electrical networks. Fiber optics can also be used in support of underground and surface services such as voice, data, LAN and video.

9.13 Conclusion Often optoelectronics is depicted, especially by those who are afraid of it as a competing technology, as a science in its infancy, with inevitable teething problems. As the costs of cables and connectors are reduced, however, the non-electrical nature of fibers will result in optoelectronics becoming more and more popular. In less than 20 years, optical fiber has revolutionized the global telecommunications network. During the next 20 years optical fiber technology can be expected to impact even more prominently by realizing new and revolutionary networks, services and applications. The provision of network facilities and capacities on a scale that is hardly imaginable today will be essential to meet the demand for both fixed and mobile telecommunications. It is anticipated, for example, that the computer will increase by 1000-fold in the next decade, and 1 000 000 fold in the decade that follows. At the same time, clock rates will increase by 10- and 100-fold respectively. But distributed computing is only effective with the availability of wide bandwidth channels between computers. Channels that are capable of data transfer rates on a par with the speed of the computers they serve. The future of fiber optics is the future of communications. With fibers, you have high bandwidth and almost unlimited potential for upgrading. Applications like multimedia and videoconferencing make high bandwidth very essential. Over wide area networks, the installed fiber optic infrastructure can be expanded to accommodate almost unlimited traffic. CATV (community antenna television or 'cable TV') operators are installing fibers very fast, since advanced digital TV will thrive in a fiberbased environment. Even wireless communications need fiber, connecting local low power cellular or PCS transceivers to the switching matrix.

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262

Optoelectronicsand Fiber Optic Technology

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During the 1990s, the use of optical fibers has increased considerably in both commercial and military environments. Without doubt, optoelectronics will become the dominating technology of the next decade.

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Appendix A Optoelectronic and fiber optic standards

The following are summarized details of some of the most important standards available today. These details have been extracted from ILI's (Infonorme London Information) Standards Infobase with their kind permission. For further details of these and other standards, the reader is recommended to visit their website at www.ili.co.uk.

Standard No.

Title

Date

Summary

EN 181000

Harmonized system of quality assessment for electronic components Generic specification fiber optic branching devices

1994

Gives a generic specification that classifies fiber optic branching devices by wavelength dependence into two sub families: wavelength selective devices and non wavelength selective devices. Coverage includes: climatic category, materials, packaging, ordering information, package marking, symbols, component marking, crush resistance, mould growth, salt mist, dry heat, cleaning of optical services, solar radiation, quality assessment procedures, and change of temperature. Also gives detailed definitions and annexes.

EN 186000 PT1

Generic specification: Connector sets for optical fibers and cables Requirements, test methods and qualification approval procedures

1993

Applies to fiber optic connector sets for optical fibers and cables. Coverage includes definitions, environmental category, gauges, corrosion resistance, component marking, package marking, spectral loss, cable torsion, cable pulling, static load, nuclear radiation, solar radiation, spectral loss, axial compression and industrial atmosphere.

EN 187102

Optical aerial telecommunication cables

1995

Covers optical aerial telecommunication cables.

EN 187200

Sectional specification Optical cables to be used along electrical power lines (OCEPL)

2001

Describes the requirements of single-mode and graded index optical fiber cables for OCEPL.

-

264

Optoelectronics and Fiber Optic Technology

Standard No.

Title

Date

Summary

EN 50173

Information Technology Generic cabling systems

1995

Specifies generic cabling for use within commercial premises that may comprise single or multiple buildings on a campus. Covers balances, copper cabling and optical fiber cabling. Specifies the structure and minimum configuration for generic cabling; implementation requirements; conformance requirements and verification procedures; performance requirements for individual cabling links.

EN 50174-1

Information Technology - Cabling installation - Part 1: Specification and quality assurance

2000

EN 50174-2

Information Technology - cabling installation installation planning and practices inside buildings

2000

This standard describes the basic requirements for the planning and operation of information technology cabling using balanced copper and optical fiber cabling. This standard is applicable to cabling designed to support particular analogue and digital telecommunications services including voice services and general cabling systems designed and intended to support a wide range of telecommunications services.

EN 50174-2

Information Technology - Cabling installation Installation planning and practices inside buildings

2000

This standard describes the basic requirements for the planning and operation of information technology cabling using balanced copper and optical fiber cabling. This standard is applicable to cabling designed to support particular analogue and digital telecommunications services including voice services and general cabling systems designed and intended to support a wide range of telecommunications services.

EN 60794 PT3

Optical fiber c a b l e s Duct, buried and aerial cablesSectional specification

1998

Gives requirements of single-mode optical fiber cables intended for use mainly in public telecommunications networks, and considers other types of applications requiring similar cable types. Particularly applies to cables for use in ducts or for directly buried application and aerial cables. Excludes submarine cables.

Appendix A - Optoelectronic and fiber optic standards

265

Standard No.

Title

Date

Summary

EN 60794-1-1

Optical fiber c a b l e s Part 1-1 - Generic specification General

1999

Applicable to optical fiber cables used with telecommunications equipment and devices which employ similar techniques. Also applies to cables consisting of electrical conductors and optical fibers. Defines uniform generic requirements for the transmission, geometric, mechanical, material, ageing (environmental exposure) and climatic properties of optical fiber cables, and electrical requirements where appropriate.

EN 60794-1-2

Optical fiber c a b l e s Part 1-2 - Generic specification - Basic optical cable test procedures

1999

Deals with optical fiber cables to be used with telecommunication equipment and devices using similar techniques, and to cables with a combination of both electrical conductors and optical fibers. Specifies methods to establish requirements for the material, transmission, geometrical, mechanical, ageing and climatic properties of cables, and electrical requirements.

EN 60825 PT2

Safety of laser products - Part 2: Safety of optical fiber communication systems

2000

Provides requirements and specific guidance for the safe use of optical fiber and/or control communication systems where optical power may be accessible at great distance from the optical source. Coverage includes: cable design, cable connectors, automatic power reduction and labelling. Also gives detailed annexes.

EN 60869-1

Fiber optic attenuators Part 1 - Generic specification

2000

Applicable to fiber optic attenuators, which are passive because they do not contain any opto-electronic or other transducing elements, have two ports for transmitting optical power and attenuate the transmitted power in a variable or fixed fashion, and that the ports are optical fibers or optical fiber connectors. Determines uniform requirements for attenuator requirements and quality assessment methods. Does not include test and measurement methods which are covered in IEC 61300-1.

266

Optoelectronics and Fiber Optic Technology

Standard No.

Title

Date

Summary

EN 60874-1

Connectors for optical fibers and cables- Part 1 Generic specification

1999

Deals with fiber optic connectors sets and single components, eg. plugs, sockets and adaptors, for all kinds, sizes and structures of cables and fibers. Covers connector set criteria and quality assessment procedures. Test and measuring methods are not included.

EN 60875-1

Fiber optic branching devices - Generic specification

2001

Applicable to fiber optic branching devices, which are passive, have three or more ports for entry/exit of optical power and share optical power in a predetermined fashion, and where the ports are optical fibers or optical fiber connectors.

EN 61202-1

Fiber optic isolatorsGeneric specification

2000

Applicable to isolators used in the field of fiber optics which have the following features: passive components which contain no opto-electronic or other transducing elements; non-reciprocal optical devices where each port is an optical fiber or optical fiber connector, or they have two optical ports for directionally transmitting optical power. Establishes uniform requirements for fiber optic isolator requirements and quality assessment procedures.

EN 61269 PT1

Fiber optic terminus sets - Generic specification

1997

Applicable to fiber optic terminus sets for all types, sizes and structures of fibers and cables, including terminus set requirements and quality assessment procedures.

EN 61274 PT1

Fiber optic adaptors - Generic specification

1997

Applies to requirements and quality assessment procedures for individual fiber optic adaptors of various types.

EN 61280-4-2

Fiber optic communication subsystem basic test procedures - Fiber optic cable plantsingle-mode fiber optic cable plant attenuation

1999

Covers methods for measurement of the optical attenuation (loss) performance in installed single-mode fiber optic cable plants. Not meant for component testing and does not specify the installation elements requiring measurement.

Appendix A - Optoelectronic and fiber optic standards

267

Standard No.

Title

Date

Summary

EN 61281-1

Fiber optic communication subsystems Generic specifications

1999

Defines a generic specification for fiber optic communication subsystems (FOCSs), and is structured according to the IEC Quality Assessment System (IECQ). Subsystems are classified by having a common sectional specification. Each are supplemented by blank detail specifications, and those appropriate to the specific individual type or types of subsystems. These parameters form a minimum set of specifications that are common to all fiber optic subsystems. Additional parameters may be needed depending on the particular application and technology. These will be in the relevant sectional specification and/or detail specification, as appropriate. Each parameter may be measured using one of these test procedures.

EN 61754 PT1

Fiber optic connector interfaces - General and guidance

1997

Describes general information on the subject of fiber optic connector interfaces, including references, definitions and rules for creating and interpreting of the standard drawings.

EN 61757-1

Fiber optic sensorsGeneric specification

1999

Defines a generic specification covering optical fibers, sub-assemblies and components as they pertain specifically to sensing application, in those aspects not already addressed by previous or concurrent standardization efforts. A sensor contains an optical or optically powered sensing element where the information is created by reaction of light to a measurand. The object is to classify, define and provide the framework for specifying fiber optic sensors, and their specific components and subassemblies, fiber optic sensors are devices for extracting information from the environment using fiber optic technology.

EN 62077

Fiber optic circulators - Generic specification

2001

268

Optoelectronics and Fiber Optic Technology

Standard No.

Title

Date

Summary

IEC 60331-25

Tests for electric cables under fire conditions - Circuit integrity Procedures and requirements Optical fiber cables

1999

Gives test procedure and the performance requirement, including a recommended flame application time, for optical fiber cables that are needed to maintain circuit integrity when subjected to fire under specified conditions. Describes continuity checking arrangements, optical testing procedure, sample preparation, the method of burning the cables and gives requirements for evaluating test results.

IEC 60747 PT5

Semiconductor devices. Discrete devices Optoelectronic devices

1995

Gives standards for the following categories or sub-categories of devices: - semiconductor photoemitters; semiconductor photosensitive devices; photocouplers, optocouplers.

IEC 60793 PT1-3

Optical fibersPart 1-3: Generic specification Measuring methods for mechanical characteristics

2000

Applicable to the tests of mechanical strength, ease of handling or the recognition of physical defects or primary coated or primary buffered optical glass fibers. The methods are to be used for inspecting fibers for commercial purposes. The aim of this part is to establish uniform requirements for mechanical characteristics of optical fibers.

IEC 60794 PT1

Optical fiber c a b l e s Generic specification

1996

Applies to optical fiber cables for use with telecommunication equipment and devices employing similar techniques and to cables having a combination of both optical fibers and electrical conductors. Presents requirements for the geometrical, transmission, mechanical and climatic characteristics of optical fiber cables, and electrical requirements. This entirely revised edition contains new measuring methods which were previously under consideration, such as torsion, snatch, kink, cable bend, temperature cycling, sheath integrity and water penetration. Temperature cycling measuring method (IEC 794-1-F1) is substituted. A guide for optical cables for short distance links is added in an annex.

Appendix A - Optoelectronic and fiber optic standards

Title

Date

Summary

60794

Optical fiber cablesProduct specifications (indoor cable)

1998

Provides product specifications for single-fiber and dual-fiber cables. Describes single-fiber optical cables for indoor use with applications such as transmission equipment, telephone equipment, data processing equipment and communication and transmission networks.

60794

Optical fiber cablesDuct, buried and aerial cablesSectional specification

1998

Specifies the requirements of single-mode optical fiber cables which are intended to be used primarily in public telecommunications networks. Other types of applications requiring similar types of cables can be considered. In particular, requirements for cables to be used in ducts or for directly buried application and aerial cables are included in this standard. Underwater cables for lakes and river crossings and cable for indoor applications will be incorporated in this standard at a later stage. For aerial applications, this standard does not cover all functional aspects of cables installed in the vicinity of overhead power lines. In the case of such applications additional requirements and test methods may be necessary.

Optical fiber cablesPart 1-1: Generic specification General

2000

Applicable to optical fiber cables for use with telecommunication equipment and devices that employ similar techniques, and to cables that are combined with both optical fibers and electrical conductors. The aim of this is to establish uniform generic requirements for the geometrical, transmission, material, mechanical, ageing (environmental exposure) and climatic properties where appropriate, of optical fiber cables and electrical requirements. Annex A - information pertinent to short-distance links for many of the cables of this specification set. Annex B - guidance for users of this specification set in procuring optical cables compliant with these specifications. Annex C - guide to the installation of optical fiber cables.

Standard No. IEC

PT2

IEC

269

PT3

IEC 60794-1-1

270

Optoelectronics and Fiber Optic Technology

Standard No.

Title

Date

Summary

IEC 60794-1-2

Optical fiber c a b l e s Generic specification Basic optical fiber test procedures

1999

Deals with optical fiber cables to be used with telecommunication equipment and devices using similar techniques, and to cables with a combination of both electrical conductors and optical fibers. Specifies methods to establish requirements for the material, transmission, geometrical, mechanical, ageing and climatic properties of cables, and electrical requirements.

IEC 60794-4-1

Optical fiber cablesAerial optical cables for high-voltage power lines

1999

IEC 60825-2

Safety of laser products Part 2: Safety of optical fiber communication systems

2000

Provides requirements and specific guidance for the safe use of optical fiber and/or control communication systems where optical power may be accessible at great distance from the optical source. Helps to protect people from optical radiation and helps to ensure adequate warning of hazards associated with optical fiber communication systems through signs, labels and instructions. Lays down requirements for manufacturers and operating organizations. Helps to reduce the possibility of injury by minimizing unnecessary accessible radiation.

IEC 60874 PT1

Connectors for optical fibers and cables - Generic specification

1999

Deals with fiber optic connectors and single components, e.g. sockets, plugs and adaptors, for all kinds, sizes and structures of cables and fibers. Covers connector set criteria and quality assessment procedures. Test and measuring methods are not included.

IEC 60875 PT1

Non-wavelengthselective fiber optic branching devicesPart 1: Generic specification

2000

Applicable to non-wavelength-selective fiber optic branching devices. It establishes uniform requirements for branching devices requirements and quality assessment procedures.

IEC 61073 PT1

Mechanical splices and fusion splice protectors for optical fibers and cablesPart 1: Generic specification

1999

Deals with fiber optic splice hardware (protection parts, alignment parts, etc) for optical fibers and cables and covers fiber optic splice hardware criteria and quality assessment methods. Test and measuring methods are detailed in IEC 61300-1, IEC 61300-2 and IEC 61300-3.

-

Appendix A - Optoelectronic and fiber optic standards

271

Standard No.

Title

Date

Summary

IEC 61073 PT2

Splices for optical fibers and cablesSectional specification- Splice organizers and closures for optical fibers and cables

1993

Covers the general requirements and the minimum quality assessment procedure for splice organizers and closures. All dimensional, mechanical and environmental requirements are to be defined in the detail specification.

IEC 61202 PT1

Fiber optic isolatorsPart 1: Generic specification

2000

Also bears the number QC 830000 which is the specification number in the IEC Quality Assessment System for Electronic Components (IECQ). Applies to the family of isolators used in the field of fiber optics, which have all of the following general features: they are non reciprocal optical devices; they are passive components in that they contain no optoelectronic or other transducing elements; they have two optical ports for directional transmission of optical power; usually they are optical fiber connectors or optical windows; they are wavelength sensitive. The object of this publication is to establish uniform requirements for the following: optical, mechanical and environmental properties of performance parameters; classification; quality assessment procedures; test and measuring methods.

IEC 61274 PT1

Fiber optic adaptors - Generic specification

1994

Relates to individual fiber optic adaptors such as: adaptors for connecting a plug to an identical type of plug adaptor; adaptors for connecting one type of plug to a different type of plug connector; adaptors for connecting a fiber optic connector to their optical devices such as LEDs, switches etc. The specification includes: adaptor requirements; quality assessment procedures.

IEC 61281-1

Fiber optic communication subsystems Part 1: Generic specification

1999

Covers a generic specification for fiber optic communication subsystems (FOCSs) which is structured according to the (IECQ), IEC Quality Assessment System. These are classified in families having a common sectional specification, each supplemented by blank detail and detailed specifications appropriate to the specific individual type or types of subsystems.

272

Optoelectronics and Fiber Optic Technology

Standard No.

Title

Date

Summary

IEC 61291-1

Optical fiber amplifiers- Part 1 Generic specification

1998

Applicable to optical fiber amplifiers (OFAs) and optically amplified, elementary subsystems using active fibers and containing rare-earth dopants. Sets out uniform requirements for transmission, operation, reliability and environmental properties of OFAs and supplies assistance to the purchaser in the selection of consistently high-quality OFA products for his especial applications.

IEC 61315

Calibration of fiber optic power meters

1995

IEC 61663-1

Lightning protectionTelecommunication lines - fiber optic installations

1999

This part is concerned with the lightning protection of telecommunication lines in fiber optic installations. Its aim is to limit the number of possible primary failures which occur in the optical fiber cable in a specified installation within values which are lower than or equal to the limit value and defined as the tolerable frequency of primary failures.

IEC 61753-1-1

Fiber optic interconnecting devices and passive components performance standard Part 1-1: General and guidanceInterconnecting devices (connectors)

2000

Gives general information on fiber optic connector performance standards. It includes references, definitions and rules for creating a performance standard. It also includes additional information pertinent to the subject.

IEC 61757-1

Fiber optic sensorsGeneric specification

1998

Gives a generic specification that covers optical fibers, components and sub-assemblies as they pertain specifically to sensing applications, in those aspects that are not already addressed by previous or concurrent standardization efforts.

IEC 61935-1

Generic cabling systems Specification for the testing of balanced communication cabling in accordance with ISO/IEC 11801 Part 1: Installed cabling

2000

Gives reference measurement methods for cabling parameters and the requirements for field tester accuracy to measure cabling parameters identified in ISO/IEC 11801. Applies when the cable assemblies are constructed of cables conforming to IEC 61156-1, IEC 61156-2, IEC 61156-3 or IEC 61156-4, and of connecting hardware as defined in IEC 60603-7 or IEC 60807-8.

Appendix A - Optoelectronic and fiber optic standards

273

Standard No.

Title

Date

Summary

IEC 61978-1

Fiber optic passive dispersion compensators Part 1: Generic specification

2000

Defines fiber optic passive dispersion compensators that are wavelength sensitive and may be polarization sensitive. Establishes quality assessment and uniform requirement procedures.

IEC 62005-1

Reliability of fiber optic interconnecting devices and passive components Part 1: Introductory guide and definitions

2001

Handbook for assessing the reliability interconnecting devices and passive components. Applicable to all types of fiber optic interconnecting devices and passive optical components.

IEC 62077

Fiber optic circulators - Generic specification

2001

Applicable to circulators used in the field of fiber optics bearing following features: - non-reciprocal optical devices, in which each port is either an optical fiber or optical fiber connector;passive components containing no opto-electronic or other transducing elements; - three or more ports for directionally transmitting optical power.

IEC 62099

Fiber optic wavelength switches - Generic specification

2001

Applicable to fiber optic wavelength switches. It covers devices and assemblies with following attributes:While the switch actuation means is by necessity active, the optical paths through the switch are passive.- The switch function is restricted to the routing of light rather than intentional power division plus routing.- They have two or more ports for the transmission of optical power and have two or more states in which power may be routed or blocked between these ports. - The ports are optical fibers or optical fiber connectors.

ISO 11149

Optics and optical instruments -lasers and laser-related equipment Fiber optic connectors for nontelecommunication laser applications

1997

Defines information for provision by a supplier of connectors between laser devices and optical fiber and optical cable assemblies.

274

Optoelectronics and Fiber Optic Technology

Standard No.

Title

Date

Summary

ISO TR 11802/4

Information Technology Telecommunications and information exchange between systems - Local and metropolitan area networks- technical reports and guidelines

1994

This publication provides the functional, electrical, optical and mechanical characteristics of a fiber optic interface for connecting a 4- or 16-Mbit/s token ring station to the trunk coupling unit (TCU) of a token ring.

ISO TR 9578

Information Technology Communication interface connectors used in local area networks

1990

Specifies the physical layer connection device for local area networks, sometimes referred to as the medium interface connector and is used between the terminal equipment and the trunk coupling unit for the trunk cable. The connectors described in this document were proposed by ISO/IEC JTC1 SC 6, SC 13, SC 83, IEC TC 46, IEC TC 48 and IEC TC 86. This document brings together the work of these groups into one collection which describes the physical devices which are currently available in the standards world.

ISO/IEC 11801

Information Technology Generic cabling for customer premises

2000

Specifies generic cabling for use within commercial premises having a geographical span of up to 3000m, with up to 1 000000 m squared of office space and a population between 50 and 50000 persons. It covers the structure and minimum configuration for generic cabling, implementation requirements, performance requirements for individual cabling links, and conformance requirements and verification procedures.

ISO/IEC 14763-1

Information Technology Implementation and operation of customer premises cabling Part 1: Administration

2001

Appendix A - Optoelectronic and fiber optic standards

275

Standard No.

Title

Date

Summary

ISO/IEC TR 14763-2

Information Technology Implementation and operation of customer premises cabling Part 2: Planning and installation

2000

Requirements are defined and provide general considerations for the planning, specification, quality assurance and installation of new cabling in accordance with ISO/IEC 11801.

ISO/IEC TR 14763-3

Information Technology Implementation and operation of customer premises cabling Part 3: Testing of optical fiber cabling

2000

The test procedures used to ensure that optical fiber cabling, designed in accordance with ISO/IEC 11801 and installed according to the recommendation of ISO/IEC 14763-2 is outlined in this report and is capable of delivering the level of transmission performance specified in ISO/IEC 11801.

Appendix B Fiber optic chronology 2500 BC: Earliest known glass.

z

800 BC:

Glass is drawn into fibers.

1790s:

Claude Chapp6 invents 'optical telegraph' in France.

1854:

John Tyndall demonstrates light guiding in water jets.

1880:

Alexander Graham Bell invents Photophone, Washington.

1880:

William Wheeler invents system of light pipes to illuminate homes from an electric arc lamp in basement, Concord, Mass.

1926:

John Logie Baird applies for British patent on an array of parallel glass rods or hollow tubes to carry image in a mechanical television. He later built an array of hollow tubes.

1930:

Heinrich Lamm, a medical student, assembles first bundle of transparent fibers to carry an image (of an electric lamp filament) in Munich. His effort to file a patent is denied because of Hansell's British patent.

1952:

Harold Horace Hopkins applies for a grant from the Royal Society to develop bundles of glass fibers for use as an endoscope at Imperial College of Science and Technology. Hires Narinder S. Kapany as an assistant when he receives grant.

1962:

Alec Reeves at Standard Telecommunications Laboratories in Harlow, UK, commissions a group to study optical waveguide communications under Antoni E. Karbowiak. One system they study is optical fiber.

1964:

Charles K. Kao takes over STL optical communication programme when Karbowiak leaves to become chair of electrical engineering at the University of New South Wales. Kao and George Hockham soon abandon Karbowiak's thin-film waveguide in favour of single-mode optical fiber.

1966:

1966:

zy zyxwvutsrq Kao tells Institution of Electrical Engineers in London that fiber loss could be reduced below 20 decibels per kilometre for interoffice communications. Kao and Hockham publish paper outlining their proposal in the

Proceedings of the Institution of Electrical Engineers.

Appendix B - Fiber optic chronology 277

1967:

British Post Office allocates an extra s some goes to fiber optics.

1972:

Maurer, Keck and Schultz make multimode germania-doped fiber with 4 decibel per kilometre loss and much greater strength than titania-doped fiber.

1975:

First non-experimental fiber optic link installed by Dorset (UK) police after lightning knocks out their communication system.

1977:

AT&T and other telephone companies settle on 850 nanometre gallium arsenide light sources and graded index fibers for commercial systems operating at 45 million bits per second.

1978:

AT&T, British Post Office and STL commit to developing a single-mode transatlantic fiber cable, using the new 1.3 micrometre window, to be operational by 1988. By the end of the year, Bell Labs abandons development of new coaxial cables for submarine systems.

1982:

MCI leases right of way to install single-mode fiber from New York to Washington. The system will operate at 400 million bits per second at 1.3 micrometres. This starts the shift to singlemode fiber in America.

1984:

British Telecom lays first submarine fiber to carry regular traffic to the Isle of Wight.

1986:

First fiber optic cable across the English Channel begins service.

1986:

AT&T sends 1.7 billion bits per second through single-mode fibers originally installed to carry 400 million bits per second.

1988: 1996:

zy

million to research;

zyxwvutsrq TAT-8 begins service of first transatlantic fiber optic cable, using 1.3 micrometre lasers and single-mode fiber.

Fujitsu, NTT Labs, and Bell Labs all report sending one trillion bits per second through single optical fibers in separate experiments using different techniques.

Glossary

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Because of their 'international acceptability' many of these definitions and terms have specific meanings and applications as opposed to generic definitions that are normally to be found in dictionaries.

Absorption: Loss of power in a fiber optic cable resulting from conversion of optical power into heat. Principally caused by impurities, such as transition metals and hydroxyl ions, it can also be caused by exposure to nuclear radiation. Acceptance angle: The half angle of the cone which incident light is totally, internally, reflected by the fiber core. It is the angle over which the core of an optical fiber accepts incoming light, usually measured from the fiber axis. It is equal to the arcsine (NA) where NA is the numerical aperture. Acceptance cone: A cone describing the complete envelope of light rays that will be propagated along an optical fiber. Active area: The area of a detector with greatest response. Amplitude modulation: A transmission technique in which the amplitude of a carrier is varied in sympathy with the information being communicated. Analog: A format that uses continuous physical parameters (such as voltage amplitude and carrier frequency) to transmit information. Angle of deviation: The angle between the original incident ray and the emergent ray. Angle of incidence: The angle between an incident ray and the normal to a reflecting or refracting surface. Angular misalignment loss: The optical power loss caused by angular deviation from the optimum alignment of source to optical fiber. Angular tilt: The angle formed by the axes of two fibers to be joined. Angular tilt causes an extrinsic loss that depends upon the joining hardware and method. Aramid yarn: Strength element used to provide support and additional protection of the fiber optic cable bundles. Kevlar is a particular brand of Aramid yarn. Armour: Extra cable protection to improve resistance to crushing, cutting and shearing forces. The usual form is a braided steel outer jacket but tough plastic with steel or plastic strengtheners is also used in many modem cable designs.

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ASCII: American Standard Code for Information Interchange. An 8-bit code in which letters, numbers and symbols are represented by 7-bit binary characters. The 8th bit is often used as a parity check. Note: The decimal numbers 0 to 47 code are used for symbols and computer commands. Decimal numbers 48 to 57 code for the numerals (0-9), decimal numbers 65 to 90 code for capital letters (A-Z), and decimal numbers 97 to 122 code for lower case letters (a-z). For example, in a computer using the ASCII code, 'A' is represented by the decimal number 65. The computer 'reads' this as the binary n u m b e r 01000001 and encodes the letter A. Most computers use an 8-bit code (extended ASCII) which produces 256 different combinations to represent symbols. In addition to the regular character set represented by ASCII (in the decimal range from 0 to 127), extended ASCII has an additional 128 codes that can be used to represent additional symbols (e.g. non-English characters or graphical symbols). Asynchronous transmission: A free-running transmission mode in which the time intervals between characters may be unequal. Attenuation: The reduction in optical power as it passes along a fiber, usually expressed in decibels (dB). See Optical loss. Attenuator: A device used to increase the attenuation of an optical fiber link, generally used to ensure that the signal at the receive end is not too strong. Avalanche photodiode (APD): A photodiode that exhibits internal amplification of photocurrent accomplished by avalanche multiplication of carriers in the junction region. As the reverse-bias voltage approaches the breakdown voltage, electron-hole pairs created by absorbed photons acquire sufficient energy to create additional electron-hole pairs when they collide with ions. A multiplication or signal gain is thereby achieved. Average power: The average level of power in a signal that varies with time. Axial ray: A light ray that travels along the axis of a fiber optic cable. Back reflection: Light reflected from the cleaved or polished end of a fiber caused by the difference of refractive indices of air and glass. Note: Typically 4 per cent of the incident light. Expressed in dB relative to incident power. Backscattering: The return of a portion of scattered light to the input end of a fiber optic cable. It is the scattering of light in the direction opposite to its original direction of propagation. Backscattering: The scattering of light in a fiber back toward the source, used to make OTDR measurements. Bandpass: A range of wavelengths over which a component will meet specifications.

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Bandwidth: 1 The information capacity of a fiber optic cable. 2 The range of signal frequencies or bit rate within which a fiber optic component, link or network will operate. 3 The difference between the lower and upper frequencies which can be sent along a communication channel. Note: When used in radio engineering, bandwidth is quoted in cycles per second (hertz, or Hz) but the word 'bandwidth' is now also used to specify digital data transmission channels and Hz then refers to bits per second. The bandwidth of Ethernet, for example, is 10 MHz (megahertz). Bandwidth-limited operation: The condition in a fiber optic-cable based communications link when bandwidth, rather than received signal power, limits performance. This condition is reached when the signal becomes distorted (principally by dispersion) beyond specified limits. Baseband: A method of communication in which a signal is transmitted at its original frequency rather than being impressed upon a carrier frequency. Baud: A unit of data transmission signalling speed equal to the number of signal symbols per second. Note: With binary modulation systems this is the same as the data transmission rate in bits per second. However, it is different with nonbinary modulation systems. Beam splitter: An optical device, such as a partially reflecting mirror, for dividing an optical beam in two or more separate beams. It can be used in a fiber optic cable data link as a directional coupler. Bend loss: Attenuation to an optical signal that occurs when an optical fiber is bent round a tight radius. Light effectively 'spills out' from the core and is lost in the cladding. Bend radius: The minimum radius around which a fiber may be curved without risk of permanent damage resulting in excessive attenuation, or even breakage. Biconic: A connector type which has a taper sleeve which would be fixed to the fiber optic cable. This was one of the earliest connectors used in fiber optic systems but is in little use at present. Binary code: A digital coding system that uses a sequence of only two types of symbols (e.g. 0 and 1) to represent data. The two symbols are called bits (an abbreviation for binary digits). Bit" A binary digit which is generally either '0' or '1.' It is the smallest representation of information in a communications a n d / o r computing system. Bit error rate (BER): 1 The percentage of bits that are incorrectly received. 2 The fraction of data bits transmitted that are received in error.

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Bit rate: The number of bits of data transmitted per second over a communications link. Bit transfer rate: The bit transfer rate is expressed as bits per second or bps. Break out cable: Same as a fan out cable. This is a multiple fiber optic cable constructed in the tight buffered design and designed for ease of connecting rugged applications a n d / o r intra-building and interbuilding requirements. Broadband: The transmission of digital data streams over a wide b a n d w i d t h channel using modulated analog signals. Several data streams can be carried simultaneously by using different carrier frequencies. Broadcast: A communication strategy in which a single communication channel is used by all the nodes in a network. Messages from any source node are received by all other nodes, but will be ignored by nodes to which they are not specifically addressed. Buffer" A protective layer over the fiber optic cable, such as a coating, an inner jacket, or a hard tube. Buffer coating: A protective layer, such as an acrylic polymer, applied over the fiber optic cable cladding. Buffer tube: A hard plastic tube, having an inside diameter several times that of a fiber optic cable, that holds one or more fiber optic cables. Buffered fiber: Fiber optic cable protected with an additional material, usually hytrel or nylon, to provide ease in handling, connecting and increased tensile strength. Bundle- Many individual fiber optic cables within a single jacket or buffer tube a n d / o r a group of buffered fiber optic cables distinguished in some fashion from another group in the same cable core. Bus" C o m m o n l y called data bus. The term is used to describe the physical linkage between stations on a network sharing a common communication. Bus network: A network topology in which all of the terminals are attached to a transmission m e d i u m serving as a bus in which all other terminals receive all signals transmitted from a terminal connected to that bus. Byte" A unit of 8 bits. Cable: One or more fibers enclosed in protective coverings and strength members. Cable assembly" Fiber optic cable that has connectors installed on one or both ends, used to interconnect multimode and single-mode fiber optic cable systems and optoelectronic equipment. Note: If connectors are attached to only one end of the cable, it is known as a pigtail. If connectors are attached to both ends, it is known as a jumper.

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Cable bend radius: During installation this infers that the cable is experiencing a tensile load. Carrier sense multiple access (CSMA): A network access procedure whereby before transmitting to the network a station checks for the presence of a carrier signal showing that the network is already being used. Transmission only starts if no other carrier is detected. Carrier sense multiple access with collision detection (CSMA/CD): A technique employed in Ethernet-based LANs to control the transmission channel. It assures that there is no conflict between terminals that wish to transmit. Carrier sense multiple access with collision detection (CSMA/CD): A type of network (e.g. Ethernet) in which all connected devices monitor continuously. If a transmitted message overwrites one already on the network, a collision is detected and the message is retransmitted. Centre wavelength: The wavelength of an optical source that might be considered its middle. Central member: The centre component of a fiber optic cable that serves as an anti-buckling element to resist temperature-induced ( a n d / o r a strength element). The central member is composed of steel, fibreglass or glass-reinforced plastic. Central office: The place where communications common carriers terminate customer lines and locate switching equipment that interconnects those lines. Centro-symmetrical reflective optics: An optical technique in which a concave mirror is used to control coupling of light from one fiber optic cable to another. Channel: 1 A communications path derived from a specific transmission medium, for example fiber optic cables. The channel supports the endto-end communications of an information source and destination. Note: Besides the transmission m e d i u m a channel needs to have a transmitter/receiver (transceiver) and a m o d u l a t o r / d e m o d u l a t o r (modem). By multiplexing, several channels can share the same specific transmission medium. Channel is s y n o n y m o u s with link. The term channel is usually employed within the context of m u l t i p l e x i n g but not always. 2 A communication path for transmission of data between two points. Chromatic bandwidth: The inverse of the chromatic dispersion. Chromatic dispersion: The temporal spreading of a pulse in an optical waveguide caused by the wavelength dependence of the velocities of light. Cladding: A low refractive index glass or plastic that surrounds the core of the fiber optic cable. Cladding mode: A mode that is confined to the cladding.

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Cleaving: The controlled breaking of a fiber so that its end surface is smooth. Coating: A material put on a fiber optic cable during the drawing process to protect if from the environment. Coherent light or light waves: Light where all parameters are predictable and correlated at any point into time or space, particularly over an area perpendicular to the direction of propagation or over time at a particular point in space. Concentrator: A multi-port repeater. Conduit: Pipe or tubing through which cables can be pulled or housed. Connector: Termination component installed on ends of fiber optic cables. It provides physical attachment and optical coupling to further cables, transmitters, receivers and other devices. Core: The centre of the optical fiber through which light is transmitted. Core eccentricity: A measure of the displacement of the centre of the core relative to the cladding centre. Coupler: An optical device that splits or combines light from more than one fiber. Coupling efficiency: The efficiency of optical power transfer between two components. Coupling losses: The power loss suffered when coupling light from one optical device to another. Coupling ratio: The percentage of light transferred to a receiving output port with respect to the total power of all output ports. Critical angle: The limiting angle at which a light ray will be totally internally reflected. Crosstalk: The pickup in one particular fiber optic cable of unwanted light from another fiber optic cable. Cut-off wavelength: The wavelength beyond which single-mode fiber only supports one mode of propagation. Dark current: The noise current generated by a photodiode when it is not exposed to any light. Data link: A transmitter, optical fiber cable and receiver that transmits digital data between two points. Data rate: The number of bits of information sent per second in a data communications transmission system. dB: Decibel, a measure of loss or equivalently attenuation. In fiber optics the ratio is power and defined by: dB = 10 lOgl0(P1/P2). Demodulation: Re-creation of an original data stream from a modulated signal. Demultiplex: Splitting up a multiplexed signal into its component parts. Detector: A device (photodiodes, photodarlingtons and phototransistors) that generates an electrical signal when illuminated by light.

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Diameter-mismatch loss: The loss of power at a joint that occurs when

the transmitting half has a diameter greater than the diameter of the receiving half. Diamond connector: A type of connector. Dichroic filter: An optical filter that transmits light selectively according to wavelength. Diffraction grating: An array of fine, parallel, equally spaced reflecting or transmitting lines that concentrate the diffracted light in a few directions, determined by the spacing of the lines and by the wavelength of the light. Digital: A data format that uses a discrete, countable and finite number of levels to transmit information. Binary is a special case of this corresponding to two levels. Digital signal: A signal encoded in discrete levels, typically binary '1' and binary '0'. Diode: An electronic device that lets current flow in one direction only. Diodes used in fiber optics include light emitters (LEDs and laser diodes) and detectors (photodiodes). Directional coupler: An optical fiber coupler where light at the input ports is only transferred to one or more defined output ports. Directivity: The amount of power observed at a given input port with respect to an initial input power. Dispersion: A general term for those phenomena that cause a broadening or spreading of light as it propagates down a fiber optic cable. Distributed system: A system containing two or more intelligent stations linked by a communication network. Dopant: A material such as germanium or boron oxide that is added to silica to change the refractive index. Drawing: The manufacturing process by which fiber optic cable is pulled from preforms. Duplex cable: A two-fiber cable suitable for duplex (two-way) transmission. Duplex transmission: Simultaneous independent transmission in both directions over a communication link. Edge-emitting diode (ELED): An LED that emits from the edge of the semiconductor chip, producing higher power and narrower spectral width. Electromagnetic radiation: Oscillating electrical and magnetic fields, perpendicular to each other, travelling at the speed of light. The spectrum includes radio waves, microwaves, infrared, visible light, ultraviolet light and X-rays. Emitter: Term used for a light source. Encoding: A scheme to represent digital ones and zeros through combining high and low voltage states.

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End separation: The distance between the ends of two joined fiber optic cables. End-to-end loss: The optical loss due to the fiber optic cable, splices and connectors on an installed fiber optic cable data link path. Endoscope: A device for transmitting an optical image along a rigid or flexible tube, used for mechanical inspection and medical instruments. Equilibrium mode distribution: The steady modal state of a multimode fiber optic cable in which the relative power distribution among the modes is independent of the fiber optic cable length. Erbium-doped fiber amplifier: A type of fiber optic cable that amplifies 1550 nm optical signals when pumped with a 980-1480 nm light source. Ethernet: A network using CSMA/CD that is widely used for LANs. Evanescent wave: Light guided along the inner part of the cladding of an optical fiber. Expanded beam connector: A connector in which the diameter of a beam of light emerging from a fiber is expanded, then focused on to the core of another fiber. Extrinsic losses: Signal loss in transmission down fiber optic cable caused by imperfect alignment of fiber optic cables joined by a connector or splice. Ferrul: A component of a connector that holds a fiber optic cable in place and aids in its alignment. Fiber: An optical waveguide consisting of thin filaments of glass with a core and a cladding which is capable of carrying information in the form of light. Fiber amplifier: An all optical amplifier using erbium or other doped fibers and pump lasers to increase signal output power without electronic conversion. Fiber bandwidth: The lowest frequency at which the magnitude of the fiber transfer function decreases to a specified fraction of the zero frequency value. Fiber bundle: An assembly of unbuffered fiber optic cables usually employed as a single transmission channel. Fiber distributed data interface (FDDI): A very high speed local area networking architecture based upon fiber optic cable as the transmission medium. Fiber distributed data interface (FDDI) network: A token passing ring network designed specifically for fiber optic cable and featuring dual counter-rotating rings and 100 Mbps operation. Fiber loss: The attenuation (deterioration) of the light signal in transmission through a fiber optic cable. Fiber optic inter-repeater link: Standard defining a fiber optic cable link between two repeaters in an IEEE 802.3 network.

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Fiber optic link: Any transmission channel using a fiber optic cable as the transmission medium to connect two end terminals or to be connected in series with other channels. Fiber optics: The branch of optical, communication and electronic technologies concerned with the transmission of electromagnetic radiation through thin fibers made of transparent material such as glass, fused silica and plastic. Fiber optic waveguide: A relatively long strand of transparent substance (usually glass) capable of conducting an electromagnetic wave of optical wavelength (visible or near-visible region of the frequency spectrum) with some ability to confine longitudinally directed, or near longitudinally directed, lightwaves to its interior by means of internal reflection. Frequency division multiplexing (FDM): Multiplexing of signals by assigning a different carrier frequency to each and then combining in a single signal. Frequency modulation: A transmission technique in which the frequency of a carrier is varied in sympathy with the information being communicated. Fresnel reflection loss: Loss of optical power due to Fresnel reflections. Fundamental mode: The lowest order propagation mode of a waveguide. Fused coupler: A method of making a multimode or single-mode coupler by wrapping fiber optic cables together, heating them and pulling them to form a central unified mass. By doing this, light on any input fiber optic cable is coupled to all output fiber optic cables. Fusion splice: A joining of two fiber optic cables by physically fusing through heat the two fiber optic cable ends. Fusion splicer: An instrument that splices fibers by fusing or welding them, typically by electrical arc. Fusion splicing: A permanent joint accomplished by the application of localized heat. Graded index fiber: A fiber optic cable where the core is composed of concentric rings of glass where the refractive indices decrease from the centre axis whose purpose is to reduce modal dispersion. Graded index profile: Any refractive index profile that varies with radius in the core. Hard-clad silica: A fiber optic cable with a hard plastic cladding surrounding a silica glass core. Hermaphrodite connector: A connector pair in which each part includes both pins (male) and sockets (female). Hybrid cable: A composite cable composed of both a fiber optic cable and electrical conductors. Hydrogen losses: Increases in fiber attenuation caused by diffusion of hydrogen.

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Incident angle: The angle between an incident ray and a line perpendicular to an optical surface.

Index matching material: A material used at an optical interconnection with a refractive index close to that of the fiber optic cable core.

Infrared: The designation for electromagnetic waves at wavelengths between the visible part of the spectrum (approximately 750 nm) and the microwave band (approximately 30 mm). Injection laser: Semiconductor or diode laser. Insertion loss: The loss in the power of a signal that results from inserting a passive component (such as in-line star couplers and splices) into a previously continuous path. Integrated optics: Design and application of optical devices that perform several functions on a single substrate. Integrated optoelectronics: Integration of optical and electronic devices on the same chip. International Standards Organization (ISO): An independent international body formed to define standards for multi-vendor network communications. Intrinsic losses: Loss caused by fiber optic cable parameter mismatches when two non-identical cables are joined. Isolator: A two-port component having greater attenuation in one direction than the other often used to prevent return reflections in a transmission path. Jacket: A layer of material surrounding an optical fiber but not bonded to it; part of the cable, not of the fiber.

Jumper cable: 1 Single fiber optics cable with connectors on both ends. 2 A short single fiber cable with connectors on both ends used for interconnecting other cables or testing. Junction laser: A semiconductor laser diode. Kevlar: A strong synthetic material used widely as a strength member and as a jacket in optical fiber cables. Xhe name is a trademark of Dupont. Large core fiber: A fiber optic cable with a core of 200 mm or more. Laser: A device which artificially generates coherent light within a narrow range of wavelengths. Lateral displacement loss: The loss of power that results from lateral displacement from optimum alignment between two fiber optic cables or between a fiber optic cable and an active device. Light: That portion of the electromagnetic spectrum that can be handled by the basic optical techniques used for the visible spectrum extending from the near ultraviolet region of approximately 0.3 mm through the visible region into the mid-infrared region of approximately 30 mm.

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Light emitting diode (LED): A semiconductor diode that spontaneously emits light from the pn junction when forward current is applied.

Light source: Source of light, typically an LED or laser, which is usually modulated and terminated over a fiber optic cable.

Lightguide: A fiber optic cable or fiber bundle. Light waves: 1 Electromagnetic waves in the region of optical frequencies. 2 The technology of optical communication, including fiber optics. Link: A fiber optic cable with connectors attached to a transmitter (source) and receiver (detector). Local area network (LAN): A data communications network serving a limited area such as a building or factory site. Local loop: The subscriber link in a telephone network. Long-haul network: A network that carries data between towns and cities, involving distances. Long wavelength: A commonly used term for light in the 1300 and 1550 nm ranges. Loose tube: A protective tube loosely surrounding a fiber optic cable often filled with a water blocking gel. Loss: Attenuation of optical signal. It is usually measured in dB. Loss budget: An account showing the overall loss in an optical fiber link, compared with the minimum received power specified at the receiver and the power available from the transmitter. Macrobend: A large fiber bend that can be seen with the unaided eye. Macrobending: Macroscopic axial deviations of a fiber optic cable from a straight line. Margin: The additional amount of loss that can be tolerated in a link. Material dispersion: Light pulse broadening caused by various wavelengths of light travelling at different velocities d o w n a fiber optic cable. Material scattering: That part of the total scattering attributable to the properties of the materials used for waveguide fabrication. Mechanical splice: A semi-permanent connection between two fibers made with an alignment device and index matching fluid or adhesive. Microbend loss: The loss attributed to microscopic bends in fiber optic cable. Microbending: Curvatures of the fiber optic cable which involves axial displacements of a few micrometres and spatial wavelengths of a few millimetres. Misalignment loss: The loss of power resulting from angular misalignment, lateral displacement and end separation. Modal bandwidth: A bandwidth limiting mechanism in multimode fiber optic cables.

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Modal dispersion: Dispersion caused by the difference in time taken by different modes to travel along a multimode fiber.

Modal noise: The fluctuation in optical power due to the interaction of the power travelling in more than one mode.

Mode: A single electromagnetic field pattern that travels in fiber. Mode coupling: The transfer of energy between modes. Mode field diameter: The diameter of the one mode of light that is being propagated in a single-mode fiber.

Mode stripper: A device that removes high order modes in a multimode fiber, to standardize conditions for measurement.

Modulation: The process by which the characteristic of one wave (the carrier) is modified by another wave (the information signal).

Multimode fiber optic cable: Type of fiber optic cable that support more than one propagation mode.

Multiplexing: Combining several data channels so that a composite signal can be transmitted over a single communications link.

Nanometre (nm): A unit of measure, 10-9m, used to measure the wavelength of light.

Network: A system of cables, hardware and equipment used for communications.

Numerical aperture: An imaginary cone which defines the acceptance area for the fiber optic cable core to accept light rays.

Optical amplifier: A device that amplifies light without converting it to an electrical signal.

Optical cable: An assembly of fiber optic cables and other material providing mechanical and environmental protection.

Optical fiber: Synonym for fiber optic cable. Optical fiber coupler: A device whose purpose is to couple power between a fiber optic cable and a source or detector.

Optical link: Any optical transmission channel designed to connect two end terminals.

Optical switch: A device that routes an optical signal from one or more input ports to one or more output ports.

Optical time domain reflectometer (OTDR): An instrument that measures transmission characteristics of an optical fiber by sending a short pulse and measuring the return signals resulting from backscatter and reflections. Optical time domain reflectometry: A method of evaluating fiber optic cables based upon detecting backscattered (reflected) light.

Optical waveguide: 1 Synonym for fiber optic cable. 2 Any structure that can guide light along a preset path. Optical window: Wavelength range of a fiber optic cable with a very low attenuation. Fiber optic data links using LED sources work in the first

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window at 850nm or in the second window at 1300nm. Fiber optic data links using LASER sources work in the second window at 1310 nm or in the third window at 1550 nm. Optoelectrical converter: Converts an optical signal into an electrical signal. Optoelectronics- The range of materials and devices that generate light (lasers and light emitting devices), amplify light (optical amplifiers), detect light (photodiodes) and control light (electro-optic circuits). Passive coupler: A coupler that divides a light input between output ports without adding any light power. Passive star coupler: Uses passive optical components to couple one or more input optical signals coming from fiber optic cables to one or more output fiber optic cables acting as receivers. Patch panel: Distribution area to rearrange fiber optic cable connections and circuits. Patchcord" A length of optical fiber or cable with optical connectors on both ends. Peak wavelength: The wavelength at which the optical power of a source is at a maximum. Phase modulation: Modulation of the phase angle of a signal in accordance with an input signal. Photocurrent" The electrical current that flows through a photosensitive device, such as a photodiode as a result of exposure to radiant power. Photodetector" An optoelectronic transducer, such as a PIN photodiode or avalanche photodiode that converts a light input into an electrical output signal. Photodiode- A semiconductor that converts light to an electrical signal, used in fiber optic receivers. Photon: A quantum of electromagnetic energy. Photonics: The technology of transmission of information using light. Pigtail: A short length of fiber optic cable, permanently fixed to a component, used to couple power between the component and the fiber optic cable used for transmission. PIN photodiode: A fast linear photodetector, widely used in fiber optic receivers. Planar waveguide" A step index multimode fiber in which a silica core is surrounded by a plastic cladding with lower refractive index. Plastic-clad silica fiber optic cable: A fiber optic cable having a glass core and a plastic cladding. Plastic fiber optic cable: Fiber optic cables having a plastic core and plastic cladding. Plastic-clad silica (PCS) fiber: A fiber made with a glass core and plastic cladding.

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Plenum: The air handling space between walls, under structural floors

and above drop ceilings which can be used to route intra-building cabling. Plenum cable: Fiber optic cables whose flammability and smoke characteristic allow it to be routed in a plenum area without being enclosed in a conduit. Point-to-point: A fixed link secured between two distinct nodes or stations in a network. Polarization stability: The variation in insertion loss as the polarization state of the input light is varied. Polarized: Light for which the electrical vector of the electromagnetic field has been oriented, instead of being at random. Polishing: Preparing the end of a fiber optic cable by moving the end over an abrasive material. Power budget: The difference (in dB) between the transmitted optical power (in dBm) and the receiver sensitivity (in dBm). Power meter: Device used to measure attenuation of a plastic fiber optic cable. Preform: A solid rod of plastic material from which a plastic fiber optic cable is drawn or a glass structure from which glass fiber optic cable is drawn. Prefusing: Fusing with low current to clean the fiber optic cable end. Precedes fusion splicing. Primary coating: The plastic coating applied directly to the cladding surface of the fiber optic cable during manufacture to preserve the integrity of the surface. Pulse coded modulation (PCM): A technique in which an analog signal is converted to a digital signal. Pulse dispersion: The lengthening of a pulse as it travels along an optical fiber. Pulse spreading: The dispersion of an optical signal with time as it propagates through a fiber optic cable. Quantum efficiency: The proportion of received photons that produce useful output current in a photodetector. Quaternary: Made from four different elements. Radiance: Optical power per unit solid angle per unit area from a source.

Radiation pattern: The angular flux distribution radiating out of a fiber.

Rayleigh scattering: The scattering of light that results from small inhomogeneities in material density or composition which causes losses in optical power varying with the fourth power of the wavelength. Receiver: A device that detects an optical signal and converts it into an electrical signal.

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Reflectance: Light that is reflected back along the path of transmission,

from either the coupling region, the connector or the terminated fiber optic cable. Reflection: The abrupt change in direction of light as it travels from one material to a dissimilar material. Refraction: The bending of light as it passes between materials of different refractive index. Refractive index: Ratio of the speed of light in a vacuum to the speed of light in a material. Regenerative repeater: A repeater designed for digital transmission that both amplifies and reshapes the signal. Sometimes called a regenerator. Regenerator: A receiver-transmitter unit that detects a weak optical signal, cleans and amplifies it, then sends the regenerated signal on through a further length of optical fiber. Repeater: One or more regenerators. Ribbon cable: A cable in which many optical fibers are embedded in parallel, in a plastic sheath, to form a ribbon-like structure. Electrical conductors may also be included. Ring network: A network topology in which terminals are connected in a point-to-point serial fashion in an unbroken circular configuration. Rise time: The time required for the leading edge of a pulse to rise from 10 per cent to 90 per cent of its amplitude. Riser: Application for indoor cables that pass between floors, normally in a vertical shaft or space. Scattering: The change of direction of light after striking small particles that causes loss in optical fibers. Scattering losses: Losses in optical fibers caused by the material of the fiber or by imperfections. Semiconductor laser: Same as a laser diode. Sensitivity: The minimum optical power required to achieve a specified level of performance. Serial transmission: A method of transmission in which each bit of information is sent sequentially on a single channel. Sheath: The outer protective layer of an optical fiber cable. Short wavelength: A commonly used term for light in the 665, 790 and 850 nm ranges. Shot noise: Noise caused by random current fluctuations arising from the discrete nature of electrons. Signal-to-Noise Ratio (SNR): The ratio of signal power to noise power measured in dB. Silica glass: Glass made mostly of silicon dioxide, used in optical fibers. Simplex: Transmission in only one direction.

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Simplex cable: A term sometimes used for a single-fiber cable. Simplex transmission: Operation of a communication channel in one direction only.

Single mode: A small core, fiber optic cable that supports only one mode of light propagation above the cut-off wavelength.

Single-mode fiber: A fiber with a small core, only a few times the wavelength of light transmitted, that only allows one mode of light to propagate. Solitron: An optical pulse that does not suffer dispersion as it propagates over a distance. Source: A LASER diode or LED used to inject an optical signal into fiber. Spectral attenuation: Measure for the attenuation in dependence on wavelength. Spectral bandwidth: The wavelength interval in which a radiated spectral quantity is not less than half its m a x i m u m value. Spectral width: The measure of the wavelength extent of a spectrum. Speed of light: Approximately 2.998 x 108 metres/second (in vacuum). Splice: An interconnection method for joining the ends of two fiber optic cables in a permanent or semi-permanent fashion. Splice box: Housing for one or more splice organizers. Splice closure: A container used to organize and protect splice trays. Splicing: The permanent joining of fiber optic cable ends to identical or similar fiber optic cables without using a connector. Star coupler: A coupler for a fiber optic cable in which power at any input port is distributed to all output ports. Star network: A network in which all terminals are connected through a single point, such as a star coupler. Station: A single addressable unit on a network, representing one or more devices that receive and transmit data. Steady state: Equilibrium mode distribution. Step index fiber: A fiber optic cable, either multimode or single-mode, in which the core refractive index is uniform throughout so that a sharp step in refractive index occurs at the core-to-cladding interface. Step index profile: A refractive index profile in which the refractive index changes abruptly from the value nl to n 2 at the core/cladding interface. Strain member: The part of an optical fiber cable which ensures that no strain is imposed on the fibers. Materials used include steel and synthetic yarns. Strength member: That part of a fiber optic cable composed of Kevlar aramid yarn, steel strands or fibreglass filaments that increase the tensile strength of the cable. Stripping: Removing the coating from a fiber optic cable.

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Subscriber loop: The link to individual subscribers in a telephone network.

Surface emitting diode: An LED which emits light from its surface rather than from its edge.

Synchronous transmission: A transmission method in which the synchronizing of characters is controlled by timing or clock signals. Transmitters and receivers operate continuously at the same frequency. Tap loss: The ratio of power at the tap port to the power at the input port. Tap port: The splitting ratio between output ports is not equal; it is the output port containing the lesser power. Tee coupler: A three-port optical coupler. Telecommunications: The communication of information over a distance by means of radio waves, optical signals or along a transmission line. Ternary: Made from three different elements. Test kit: A kit of fiber optic instruments, typically including a power meter, source and test accessories used for measuring loss and power. Thermal noise: Noise resulting from thermally induced random fluctuation in current in the receiver's load resistance. Thermal stability: A measure of the insertion loss variation as the device undergoes various environmental changes. Threshold current: The minimum current needed to sustain laser action in a laser diode. Throughput loss: The ratio of power at the throughput port to power at the input port.

Tight buffer: 1 Type of cable construction whereby each glass fiber optic cable is tightly buffered by a protective thermoplastic coating to a diameter of 900 microns. 2 A material tightly surrounding a fiber in a cable, holding it rigidly in place. Time division multiplex (TDM): Digital multiplexing by taking one pulse at a time from separate signals and combining them into a signal bit stream. Time division multiplexing (TDM): A transmission technique whereby several low speed channels share a given transmission medium, for example a fiber optic cable. Token: A unique bit sequence which permits a station to transmit to a token ring network. Token ring network: A network that can only be accessed by a station that is allocated the token, which is passed around the network in a predetermined sequence. Total bandwidth: The combined modal and chromatic bandwidth. Total internal reflection: Confinement of light into the core of a fiber by the reflection off the core/cladding boundary.

zy zyxwvut Glossary

295

Transceiver: A combination of transmitter and receiver providing both output and input interfaces with a device.

Transduce: A device for converting energy from one form to another, such as optical energy to electrical energy.

Transmission loss: Total loss encountered in transmission through a system.

Transmission media: The physical media through which communication signals are transmitted, for example optical fiber, coaxial cable, twisted pairs.

Transmitter: 1 An electrical package which converts an electrical signal to an optical signal. 2 A device which includes an LED or laser source and signal conditioning electronics that is used to inject a signal into fiber. Transparency: A communication system which is transparent and imposes no restrictions on the code or bit patterns in the information being transmitted. Tree coupler: A coupler which distributes light signals to several output ports. Ultraviolet: Electromagnetic waves with wavelengths around 100 to 400 nm. Uniformity: The maximum insertion loss difference between ports of a coupler. Videophone: A telephone service that offers transmission of pictures as well as sound. Virtual reality: A computer simulation that closely resembles reality. Visible light: Electromagnetic radiation that is visible to the h u m a n eye, at wavelengths from 400 to 700 nm. Waveguide: A two-dimensional substrate which carries light in channels inscribed in the material. Wavelength: Distance an electromagnetic wave travels in the time it takes to oscillate through a complete cycle. Wavelength dependence: The variation in an optical parameter caused by a change in the operating wavelength. Wavelength division multiplexer: A passive fiber optical device used to separate optical signals of different wavelengths carried on one fiber optic cable. Wavelength division multiplexing (WDM): Simultaneous transmission of several optical signals of different wavelengths on the same fiber optic cable. Wide area network (WAN): Communication network covering long distances, often using some public network facilities. Working margin: The difference (in dB) between the power budget and the loss budget (i.e. the excess power margin).

Acronyms and abbreviations

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ACOST: UK Advisory Council on Science and Technology ACR: Attenuation to Crosstalk Ratio Al: Aluminium AM: Amplitude Modulation APD: Avalanche PhotoDiode APF: All Plastic Fiber As: Arsenide ATM: Asynchronous Transfer Mode BBC: British Broadcasting Company BER: Bit Error Rate bit: Binary digit CAD: Computer Aided Design CATV: Community Antenna Television (or cable TV) CPU: Central Processor Unit CSMA: Carrier Sense Multiple Access CSMA/CD: Carrier Sense Multiple Access with Collision Detection CSP: Channelled Substrate Planer (LASER) DARPA: US Defense Advanced Research Projects Agency dB: Decibel dB(mu): Optical power referenced to 1 microwatt dB/km: Decibels per kilometre dBm: Optical power referenced to 1 milliwatt dBr: Decibels relative to a known power level DC: Direct Current DFB: Distributed FeedBack DOT: Department of Transport DSB: Digital Signal Processing DSF: Dispersion Shifted Fiber DTI: Department of Trade and Industry D W D M : Dense Wavelength Division Multiplex(ing) EDFA: Erbium-Doped Fiber Amplifier EDTFA: Erbium-Doped Tellurite Fiber Amplifier EFTA: European Free Trade Association EIA: Environmental Impact Assessment EIA: Electronic Industries Association ELED: Edge Light Emitting Diode ELFEXT: Equal Level Far End Cross Talk EMC: ElectroMagnetic Compatibility

zy zyxwvutsrq Acronyms and abbreviations 297

EMD: Equilibrium Mode Distribution EMI: Electromagnetic Interference EU: European Union FDDI: Fiber Distributed Data Interface FDM: Frequency Division Multiplex(ing)

FEXT: Far End Cross Talk FIA: Fiber Industry Association FITL: Fiber In The Loop FLOD: Full Length Outside Deposition FM: Frequency Modulation FO: Fiber Optic FOA: Fiber Optic Amplifier FOTP: Fiber Optic Test Procedure FOTS: Fiber Optic Transmission System FPLD: Fabry-Perot Laser Diode FTTB: Fiber To The Building FTTC: Fiber To The Curb FTTH: Fiber To The Home FWHM: Full Width Half Maximum FXC: Fiber switch Cross Connect Ga: Gallium Gbit: Gigabit GI: Graded Index GIPFOC: Graded Index Plastic Fiber Optic Cable GOF: Glass Optical Fiber IDF: Intermediate Distribution Frame IDP: Integrated Detector/Amplifier ILD: Index guided Laser Diode ILD: Injection Laser Diode In: Indium IR: Infrared ISDN: Integrated Services Digital Network ISO: International Standards Organization kg: Kilogram km: Kilometre km/s: Kilometres per second LAN: Local Area Network LASER: Light Amplification by Stimulated Emission/Radiation lb: Pound (weight, UK) LD: Laser Diode LED: Light Emitting Diode LLDPE: Linear Low Density PolyEthylene jacketing LLIDS: Local Light Injection and Detection System LPE: Liquid Phase Epitaxy

298

zyxwv zyxwv

Optoelectronicsand Fiber Optic Technology

LSFH: Low Smoke Halogen Free

m: Metre mA: MilliAmpere M A N : Metropolitan Area Network MBE: Molecular Beam Epitaxy M B P S : (see Fiber distributed data interface network in the Glossary) MCRW: Metal-Clad Ridge Waveguide (laser) MDF: Main Distribution Frame M E M S : Micro ElectroMechanical Systems M H z : MegaHertz mm: Millimetre MMF: Multimode Fiber optic cable

MOCVD: Metal Organic Chemical Vapour Deposition M o d e m : Modulator/demodulator

MOVPE: Metal Organic Vapour Phase Epitaxy MRI: Magnetic Resonance Imaging mW: MilliWatt NA: Numerical Aperture NEXT: Near End Crosstalk NIR: Near Infrared NIU: Network Interface Unit NLO: Non-Linear Optics nm: Nanometre NTSC: National Television System Committee OSI: Open Standards Interconnect OTDR: Optical Time Domain Reflectometer P: Phosphorous PAL: Phase Alternation Line (European TV format) PCB: Printed Circuit Board PCM: Pulse Code Modulation PCS: Plastic Clad Silica PD: Potential Difference PD: Photodiode PDFFA: Praseodymium-Doped Fluoride Fiber Amplifier PE: Polyethylene. This is a type of plastic material used to make cable jacketing PET: Position Emission Tomography PF: Perfluorinated PIN: Positive Intrinsic Negative photodiode PIN-FET: PIN-Field Effect Transistor PIN-PD: PIN-Photodiode P M M A : Polymethylmethacrylate POF: Plastic Optical Fiber POFA: Plastic Optical Fiber Amplifier

zy zyxwvutsr Acronyms and abbreviations 299

PSTN: Public Switched Telephone Networks PTFE: Polytetrafluoroethylene (Teflon) PTT: Postal Telegraph and Telephone PUR: Polyurethane PVC: Polyvinyl Chloride R&D: Research and Development RF: Radio Frequency RI: Reflective Index RX: Receiver SC: A connector type, primarily used with single-mode fiber optic cables ScTP: Screened Twisted Pair SDM: Space Domain Multiplexing Si: Silicon SIPFOC: Step Index Plastic Fiber Optic Cable SLB: System Loss Budget SMA: Sub Multiple Assembly SMA: A connector type that was the predecessor of the ST connector SNR, S/N: Signal to Noise Ratio. Usually expressed in dB SOA: Semiconductor Optical Amplifier SONET: Synchronous Optical Network ST: A keyed bayonet connector type similar to a BNC connector STL: Standard Telecommunications Laboratories TDM: Time Division Multiplex(ing) TIA: TransImpedence Amplifier TIR: Total Internal Reflection TX: Transmitter UK: United Kingdom US: United States UTP: Unshielded Twisted Pair UV: Ultraviolet VCSEL: Vertical Cavity Surface Emitting Laser VCSL: Vertical Cavity Semiconductor Laser VLON: Virtually Lossless Network VLSI: Very Large Scale Integration W: Watt WAN: Wide Area Network WDM: Wavelength Division Multiplex(ing) WIC: Wavelength Independent Coupler

Books by the same author

7~t/e

Details

Publisher

ISO 9001:2000 for Small Businesses (Second Edition)

Fully revised and updated, ISO 9001:2000 for Small Businesses explains the new requirements of ISO 9001:2000 and helps businesses draw up a quality plan to allow them to meet the challenges of the marketplace.

Butterworth-Heinemann ISBN: 0 7506 4882 1

ISO 9001:2000 Audit Procedures

A complete set of audit check sheets and explanations to assist auditors in completing internal, external and third part audits of newly implemented ISO 9001:2000 Quality Management Systems, existing ISO 9001:1994, ISO 9002:1994 and ISO 9003:1994 compliant QMSs and transitional QMSs

Butterworth-Heinemann ISBN: 0 7506 5436 8

ISO 9001:2000 in Brief

A 'hands-on' book providing practical information on how to cost effectively set up an ISO 9001:2000 Quality Management System.

Butterworth-Heinemann ISBN: 0 7506 4814 7

CE Conformity Marking

Essential information for any manufacturer or distributor wishing to trade in the European Union. Practical and easy to understand.

Butterworth-Heinemann ISBN: 0 7506 4813 9

Environmental Requirements for Electromechanical and Electronic Equipment

Definitive reference containing all the background guidance, ranges, test specifications, case studies and regulations worldwide.

Butterworth-Heinemann ISBN: 0 7506 3902 4

MDD Compliance using Quality Management Techniques

Easy-to-follow guide to MDD, enabling the purchaser to customize the Quality Management System to suit his own business.

Butterworth-Heinemann ISBN: 0 7506 4441 9

Quality and Standards in Electronics

Ensures that manufacturers are aware of the all the UK, European and international necessities, knows the current status of these regulations and standards, and where to obtain them.

Butterworth-Heinemann ISBN: 0 7506 2531 7

Use ful lin ks

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www.ailu.org.uk: AILU is an independent non-profit-making organization serving the industrial laser industry to help make the most of laser technology. Primarily a source of technical, product and service data on industrial lasers and their applications. Includes industry directory, online catalogue and events notice board. Also offers courses. www.alertt.org.uk: ALERTT is a DTI funded project run by the UK Consortium for Photonics and Optics to provide a national database on activities in photonics. www.auriga-europe.co.uk: AURIGA is a specialist optoelectronics and fiber optic distributor who offers a combination of copper, fiber optic and wireless products to suit all networking needs. They started trading in 1989 and have negotiated partnerships with blue chip manufacturers such as 3M, AMP, BICC Brand-Rex and Diamond. AURIGA. www.brand-rex.com: Part of the newly formed Intelligent Building Systems sector of Novar Plc, Brand-Rex is a major global supplier of structured cabling systems for data networks and a world leader in cabling solutions for the military, naval, aerospace, communication, automotive and mass transit industries. www.corning.com: Corning Cable Systems, wholly owned by Corning Incorporated (NYSE: GLW), provides system solutions and services for the various communication networks of all applications ranging from trade and industry through to universities and research institutes. The product range comprises cabling systems with fiber optic or shielded and unshielded copper cables with the appropriate hardware for campus, building and home cabling. www.fibreoptic.org.uk: Formed in February 1991, the aims and objectives of the Fibre Optic Industry Association Ltd (FIA) are to promote high standards of service within the fiber optic industry and to represent its members at a national and international level. FIA is committed to assisting the creation of standards, practices and guidelines for manufacturers, installers and users of fibre optics. www.fotec.com: Fotec has twenty years of experience in fiber optics, building test equipment and training. It provides technical support, online courses, and links to an online store where you can purchase training programs and cabling products. This website has lots of useful information whether you are just getting started or are trying to locate some references.

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Optoelectronics and Fiber Optic Technology

www.herne.org.uk: Herne European Consultancy Ltd specialize in the

development of Quality Management Systems that meet the recommendations and the specifications contained in the ISO 9000 (quality system and quality assurance) standards and the ISO 14000 (environmental management system) standards. They also specialize in designing and implementing internal and external audit procedures and are available to complete impartial, third party audits to suit the customer concerned. www.iee.org.uk: The IEE is involved in all aspects of photonics, including optical communications, optoelectronics devices and optical fiber sensors, thermal imaging and lasers. Has Optical Technology and Applications special interest group. www.ili.co.uk: Founded in 1949, ILI are specialists in worldwide hardcopy Standards and Specifications (DIN, ISO, BSI, ASTM, NFPA, API, IEC, ASME, etc.) and hold huge stocks for sale from distribution centers in Europe and the US. ILI also publish a range of engineering, technical and regulatory databases. www.iop.org/www.olemag.com: Runs a number of special interest groups including the Quantum Electronics Group and the Optical Group. Also publishes monthly magazine. www.kdoptics.com: KD Optics designs and manufactures optical test equipment for use in the fibre optic and datacomms and telecomms industry. In addition to a range of hand held equipment, there is a complete range of bench style fibre test equipment for use in manufacturing and test environments. www.lasirvis.com: LasIRvis are specialist distributors of fiber optic components, driver boards, collimators, modules and special assemblies such as Thermo Electric Coolers (peltier effect). OptoGuard HSR (for high precision applications) and encoder products. LaslRvis also produce fiber to component assemblies using PMMA, (plastic/acrylic multi mode fiber) for fiber pigtailed lasers, detectors and special emitters. www.mma.org.uk: Run by the Institution of Mechanical Engineers with the support of the DTI. MMA encourages the commercial exploitation of microsystems technology and nanotechnology. www.nettest.com: NetTest (formerly GN Nettest) is a leading worldwide provider of testing, monitoring and management systems across both the optical and network layers of communications networks. NetTest provides network operators, network equipment manufacturers, component manufacturers and enterprise service providers with the network testing solutions they need. www.noyes-fiber.com: Noyes is an industry leader in the design and manufacturing of fiber optic test equipment for measuring, maintaining and documenting the performance of fiber optic networks. Product line consists of DWDM, optical power meters, light sources, loss/

Useful links

303

return test sets, fiber certification kits, mini-OTDRs, fiber inspection scopes, fiber optic talk sets, visible fault and fibre optic identifiers. www.nmi.org.uk" Primarily aimed at the semiconductor industry it provides a mechanism for collaboration between its members, educational organizations, regional bodies and government. Has established a UK-wide education and training strategy for the industry. www.opticspages.com: Optics P a g e s - 'the quickest Optics Industry Directory Online'. It has detailed and searchable lists of companies, products and relevant publications. www.optoelectronics.org.uk: Organizes events and meetings. www.osda.org.uk: OSDA is the successor to the DTI-funded LINK Photonics programme to support collaborative research between industry and academia on the application of optical techniques and devices. The five year, s million OSDA programme runs until 2005 and will focus on optical communications, imaging and sensors, high efficiency lasers, and optics in computers and displays. The site has links to descriptions of projects supported under the LINK Photonics programme. www.photonics.ca/cpc: This site contains detailed on-line publications dealing with the Canadian photonics industry, along with an events diary. www.photonics.crc.org.au: Run by the Australian Photonics Cooperative Research Centre, a joint venture between five Australian universities and industry and business, this site concentrates on photonics for the telecommunications industry. It describes current R&D projects and has an excellent education section with on-line mini tutorials in communications and basic photonics. www.pro.on.c a: This site contains up-to-date news items of general interest as well as those relating specifically to the Canadian industry. There are also on-line newsletters and annual reports. www.qaphotos.com: Jim Byrne and Diana Craigie founded QA as a photographic company specialising in tunneling and large construction projects. Jim goes world-wide taking photos for clients and Diana now runs the photographic library. www.royalsignals.army.org.uk: The Royal Corps of Signals Museum (located in Blandford Camp, Dorset) is the national museum of Army communications and contains exhibits and displays showing the part that communications have played in the many wars and campaigns during the last 150 years. The Museum collection is regarded as being of national importance and the excellent Archives are recognized by the Public Records Office. www.scottyweb.co.u k: David Scott is a freelance photographer based in Manchester, UK. The site, run by a small team with sponsorship from

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304

Optoelectronicsand Fiber Optic Technology

zyxwv

small UK businesses, provides a platform for promoting diverse and dynamic photographic content from around the world. www.sepnet.org.uk: SEPNET is a group of businesses, research organizations, universities and support bodies in Southeast England aimed at developing the commercial application of photonics, optoelectronics, laser machining and microsystems. www.sid.org.uk: SID is a global non-profit voluntary technical society dealing with display technologies and applications. It has an active UK chapter and provides links to many other related sites. www.spie.org" US-based organization, SPIE has technical groups and discussion forums on all aspects of optics, photonics, optical fibres and lasers. It runs meetings, conferences and technical programmes. It also has an on-line bookshop selling books, videos and CDs, and contains an excellent education section. SPIE also publishes OE magazine, a monthly news bulletin on optics and optoelectronics. [email protected]" StingRay Technical are available for commissions to research and write reference books (on most subjects); technical manuals, user handbooks, etc. All technical literature is aimed at being well structured and simple to read. www.terahertztechnologies.com 9A US-based site that provides links to sources of information on photonics and optoelectronics around the world. Information sources are classified into magazines, societies and organizations, universities, research centres and national laboratories www.tycoelectronics.com: Tyco Electronics offers a broad range of high quality electronic component products. Products from well-known brand names include connectors/interconnection systems, terminal blocks, relays, electronic modules, circuit protection devices, fiber optic components, wire and cable, switches, wireless components, sensors, printed circuit boards, touchscreens and application tooling. www.ukleo.org: UKLEO is the trade association for suppliers of optoelectronics and photonics equipment and services. It provides a single voice for the industry and lobbies on its behalf. It sponsors trade exhibitions and technical conferences. www.ukcpo.org.uk: UKCPO acts as the umbrella organization for photonics in the UK, linking trade associations, professional organizations, and manufacturers, researchers and users.

zyxw zy

Index

zyxw

zyxwvutsr

Absorbtion, definition, 278 Acceptance angle (numerical aperture), 48-49, 50, 278 Acceptance cone, 47-48, 278 ACOST see UK Advisory Council on Science and Technology Acrylic adhesive, 168 Active area, definition, 278 Admiralty shutter telegraph, 3-5 AEG Telefunken, 89 Aeschylus, 2 Agere, 236 Agilent, 235 Airplane design using fiber optics, 260 A1GaAs see Aluminium gallium arsenide A l m a g e s t (Ptolemy), 37 Aluminium gallium arsenide, 113-14 American Standard Code for Information Exchange (ASCII), definition, 279 American Telephone and Telegraph (AT&T), 277 Amplifier design, 138-41 Amplitude modulation, definition, 278 Anaerobic adhesive, 167-68 Analog, definition, 278 Andromeda computer, 251 Angle of deviation, definition, 278 Angle of incidence, 45, 278 Angular misalignment loss, definition, 278 Angular tilt, definition, 278 Anthropological telegraph, 8 APD see Avalanche photodiode Application Specific Optical Component (ASOC), 236

Aramid yarn, definition, 278 Argon/KTP lasers, 259 Armiento, Craig, 129 Armour, definition, 278 ASCII s e e American Standard Code for Information Exchange ASOC s e e Application Specific Optical Component Asynchronous transfer mode (ATM), 194, 279 AT&T s e e American Telephone and Telegraph Attenuation, definition, 279 Attenuation test equipment, 217 Attenuator, definition, 279 AURIGA (Europe) PLC, 76, 162, 163, 178 Avalanche photodiode (APD), 132, 135, 248, 279 Average power, definition, 279 Axial and angular fiber misalignment losses in couplers, 159 Axial ray, definition, 279

Babinet, Jacques, 10 Back reflection, definition, 279 Backscattering, definition, 279 Bainoski, Dr Michael, 225 Baird, John Logie, 14, 276 Ballistic transport of electrons, 237 Balloon signalling, 10 Bandpass, definition, 279 Bandwidth: definition, 280 measurement equipment, 217, 231-32 of optoelectronic transmission systems, 62-65

306

Index

zyxwvutsrq

Bandwidth-limited operation, definition, 280 Baseband, definition, 280 Baud, definition, 280 Beam splitter, definition, 280 Bell, Alexander Graham, 10, 11-13, 276 Bell Laboratories, 18, 128, 249, 253, 277 Bend loss, definition, 280 Bend radius, definition, 280 Bending diameter of cables, 92-93 BER s e e Bit error rate BH s e e Buried heterostructure of laser diodes BICC s e e British Insulated Callender Cables Biconical tapered transmissive mixer, 71,280 Binary code, definition, 280 Bit error rate (BER), definition, 280 Blandford Camp shutter telegraph station, 4, 5 Blown optical fiber, 211-15 advantages, 212, 214 Blolite system, 215 equipment, 214-15 Bookham Technologies, 236 Bragg mirror, 127, 128, 240 Break out cable, definition, 281 British Insulated Callender Cables (BICC) Brand-Rex, 55, 96, 99, 104, 175, 177, 183, 211,213, 215 British Post Office, 17, 277 British Telecom, 139, 211,277 Broadband, definition, 281 Broadcast, definition, 281 Buffer, definition, 281 Buffer coating, definition, 281 Buffer tube in cable design, 93-95, 281 Buffered fiber, definition, 281 Bundle, definition, 281 Buried heterostructure of laser diodes, 124 Bus, definition, 281 Bus network, definition, 281 Byte, definition, 281

Cable: assembly, definition, 281 bend radius, definition, 282 construction, 98-99 definition, 281 ducts, 97 jointing s e e Jointing/splicing of fibers routing s e e Routing of optical fiber cables types, 95-97 Cable Talk Pty Ltd, 20 Campus cabling for fiber optics, 197-99 Cap sealing techniques, 90-91 Car design using fiber optics, 260 Carbon dioxide laser, 259 Carrier sense multiple access (CSMA), definition, 282 Catastrophic optical damage (COD), 114 Central member, definition, 282 Central office, definition, 282 Centre wavelength, definition, 282 Centro-symmetrical reflective optics, definition, 282 Channel, definition, 282 Channelled substrate planer, 124 Chapp6, Claude, 5, 6, 276 Chromatic bandwidth, definition, 282 Chromatic dispersion, definition, 282 Chronology of fiber optics, 276-77 Cladding of an optical fiber, 47-50, 92, 282 Cleavers for fiber optics, 160-62, 283 Coating, definition, 283 COD s e e Catastrophic optical damage Coherent light, 109, 283 Collodon, Daniel, 10 Colour coding of optical fibers, 97 Communication systems, 182-214: s e e a l s o Fiber optics; Future developments; Optoelectronics; Technology of fiber optics data networks, 188-91 local area network (LAN), 189, 194 metropolitan area network (MAN), 189-90

zyxwvutsrq

Index

wide area network (WAN), 190-91, 194 design of an optical fiber system, 191-201 alternative types compared, 195, 196 asynchrous transfer mode (ATM), 194 cable routing see Routing of optical fiber cables comparison with copper cable, 192-93 digital or analog, 193-94 distribution, 194 ethernet, 194 fiber losses, 196-97, 201-203 multiplexing, 194, 196 system loss budget (SLB), 201-203 local networks, 184-87 comparison with coaxial system, 186 line terminating unit (LTU), 185-86 optical fibers advantages, 184-85 long distance networks, 187 telephone networks, 187-88 Communications and fiber optics, 261-62 Comparisons of types of fiber, 83, 84 Computing and optical technology, 251-52, 260-61 Concatenation of cables, 152 Concentrator, definition, 283 Cond6 telegraph post, 6 Conduit, definition, 283 Connectors, 1 4 2 - 5 2 : s e e also Couplers; Jointing/splicing; Receivers; Transmitters; attachment to a fiber, 160-62 attenuation, 144-45 definition, 142, 283 for fiber bundles, 149-50 for hybrid cables, 151-52 insertion loss, 145 quality, 143 requirements, 143 for single fibers, 148-49

307

zy

stick and turn (ST), 147, 148 sub multiple assembly (SMA), 145, 148 types available, 145-46 Converting light into electrical energy, 132-34 Copernicus, Nicolaus, 37 Core eccentricity, definition, 283 Core of an optical fiber, 47-50, 283 Corguide dispersion-flattened single-mode fiber, 116 Corning Cable Systems GmbH, 19, 33, 96, 101, 102, 103, 143, 150, 174, 176, 197, 198, 200, 202, 211, 237 Corning Glass Works, 17-18, 60, 82, 116, 179, 243 Couplers, 152-64 concatenation, 152 definition, 283 end fire, 152-53, 163-64 evanescent wave, 164 insertion losses, 145, 158-60 angular and axial misalignment, 159 Fresnel losses, 160 lens, 154 multiport, 154-58 four-port, 156-57 as signal dividers, 158-59 as switches, 157 symmetrical and asymmetrical, 155-56 in transmissive or reflective mode, 158 Coupling efficiency, definition, 283 Coupling losses, definition, 283 Coupling ratio, definition, 283 Coxwell, Henry, 10 Crimping of fibers, 168 Critical angle, 46-47, 283 Crosstalk, definition, 283 CSMA Carrier sense multiple access, definition, 283 CSP see Chanelled substrate planer Cured epoxy for jointing, 166-67 Curvature sensors using fiber optics, 259 Cut-off frequency of a fiber, 63 Cut-off wavelength, definition, 283 Cyanoacrylate adhesive, 167

zyxwvuts

308

zyxwvutsrq

zyxwvutsr

Index

Dark current noise, 69, 283 DARPA see U.S. Defence Advanced Research Projects Agency Data link, definition, 283 Data networks, 188-91 local area network (LAN), 189, 194 metropolitan area network (MAN), 189-90 wide area network (WAN), 190-91, 194 Data rate, definition, 283 Datacom Ltd, 222 Decibel (dB), definition, 283 Decker, C.D., 129 Decorations using fiber optics, 257 Deflecting diameter of cables, 92-93 Demodulation, definition, 283 Demultiflex, definition, 283 Dense wavelength division multiplexing (DWDM), 74, 229, 238, 240, 243, 249 Department of Trade and Industry (DTI), 233 Department of Transport (DOT), 258 Descartes, Ren6, 42 Despencer, Lord le, 3 Detector, definition, 283 Deutsche Bundespost, 246 DFB see Distributed feedback laser Diameter-mismatch loss, definition, 284 Diamond connector, definition, 284 Dichroic filter, definition, 284 Diffraction grating, definition, 284 Diffused gallium arsenide, 112-13 Digital, definition, 284 Digital signal, definition, 284 Diode, definition, 284 Directional coupler, definition, 284 Directivity, definition, 284 Dispersion losses in fibers, 58-60 chromatic dispersion, 59-60 definition, 284 dispersion-shifted fiber, 60 material dispersion, 58 waveguide dispersion, 58-59 Distributed feedback laser (DFB), 240

Distributed system, definition, 284 Distribution frames for fiber optics (patch panels), 201, 210-11 Dopant, definition, 284 Doppler effect in fiber optics, 239 Dorset Police, fiber optic link, 277 DOT see Department of Transport Drawing, definition, 284 DTI see Department of Trade and Industry Duplex cable, definition, 284 Duplex transmission, definition, 284 DWDM see Dense wavelength division multiplexing

EDFA see Erbium doped fiber amplifier EDFFA see Erbium doped fluoride fiber amplifier Edge emitting diode (ELED), 111-12, 119, 284 EDTFA see Erbium doped tellurite fiber amplifier EFTA see European Free Trade Association Elastomeric splicer, 173 Electromagnetic spectrum, 19-20, 284 E l e c t r o n i c s , 15 ELED see Edge emitting diode E l e m e n t s (Euclid), 36 Emitter, definition, 284 EN Standards, 263-67 Encapsulated fibers, 244-45 Encapsulating lasers, 241-43 Enclosure design for jointing fibers, 179-80 Encoding, definition, 284 End fire couplers, 152-53 End fire mixers, 70-71 End separation, definition, 285 End-to-end loss, definition, 285 Endoscope, definition, 285 Epitaxial layer, 122 Epoxy splice procedure, 166 Equilibrium mode distribution, definition, 285

Index

Erbium doped: fiber amplifier (EDFA), 139-40, 236, 238, 240, 243, 285 fluoride fiber amplifier (EDFFA), 140 tellurite fiber amplifier (EDTFA), 140-41 Er:YAG laser, 259 Ethernet, 189, 194, 285 Euclid, 36 European Community, 233-34 European Free Trade Association (EFTA), 234 European optical fiber market, 235 Evanescent wave coupling, 164, 285 Expanded beam connector, definition, 285 External ducted cable, 99 External vapour deposition in manufacturing, 86-87 Extrinsic losses, definition, 285

309

amplifier, definition, 285 background and history, 1-19 bandwidth, definition, 285 basic design principles, 15, 19-22 bundle, definition, 285 cable, 22 capacity, 19 definition, 1,285, 286 disadvantages, 29-31 cost, 29 energy losses, 30-31 jointing and testing, 29-30 drawing during manufacture, 88-89 future applications, 233-62 gyroscope, 255-56 inter-repeater link, 285 loss, definition, 285 optical waveguide, 16-17, 18 receiver, 22 regenerator, 22 total internal reflection (TIR), 13-15 tracers, 221-23 transmitter, 19 waveguide, definition, 286 Fiberless transmission of signals, 248-49 FiberMeter (Datacom), 224-25 FiberProbe (Datacom), 222 Field effect transistor amplifier (FET), 248 Field testers for fiber optics, 224-25 FLOD s e e Full length outside deposition Fluoride glasses for optical fibers, 237-38 Fotec, 166, 168, 221,222 DM3000 power meter, 222 Fiber U OTDR, 229-30 $660 Fotracer, 222 $665 visual fault locator, 221 France, optical fiber market, 234 Frequency division multiplex signals (FDM), 67, 187, 286 Frequency modulation of optoelectronic transmission, 67, 286 Fresnel reflections, 160, 227, 228, 286

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zyxwvutsr

Fabrey-Perot cavity, 128, 246 Fast ethernet, 194 FDM s e e Frequency division multiplex signals Ferrul, definition, 285 FET s e e Field effect transistor amplifier Fiber distributed data interface (FDDI), definition, 285 Fiber Industry Association (FIA), 208 Fiber optics: s e e a l s o Future developments; Optoelectronics; Receivers; Technology of fiber optics advantages, 23-28 analog and digital transmission, 28 electrical insulation, 27 flexibility, 26-27 immunity to electrical fields, 24, 27, 28 low attenuation, 25 receiver sensitivity, 28 small size and weight, 25-26 wide transmission bandwidth, 25

310

Index

zyxwvutsrq

Fujikura high precision fiber cleaver, 160-62, 176 Fujitsu, 277 Full length outside deposition (FLOD) in manufacture, 89-90 Fundamental mode, definition, 286 Fused coupler, definition, 286 Fusion splicing, 174-79, 286 graded index fibers, 177 multi-fibers, 178-79 procedure, 174-77 single-mode fibers, 178 Future developments, 233-62 ballistic transport, 237 car and airplane design, 260 commercial applications, 233 in communications, 261-62 curvature sensors, 259 distributed feedback laser (DFB), 240 encapsulated fibers, 244-45 fiber optic gyroscope, 255-56 fiberless transmission, 248-49 fluoride glasses, 237-38 global market, 233-35 increased bandwidth, 246-48 internet, 260 laser dazzler, 253-54 leak detection, 250 medical uses, 258-59 military applications, 253-56 mining, 261 modular lasers, 241-43 moulded-clad single-mode fibers, 243 moveable fibers, 246 multi-core fibers, 243-44 office lighting, 256-57 optical, bus, 246 computing, 251-52, 260-61 ether, 249-50 multiplexers, 252 processing, 260-61 radio, 250 sensors, 256 opto-isolators, 252 optoelectronic switches, 252-53

plastic opto-chips, 254-55 polarization of light, 238 porous silicon, 237 rare earth doped optical fibers, 240-41 solitron pulses, 238-39 synchronous optical network (SONET), 238 temperature monitor using optical fiber, 251 tunable lasers, 240 UK market, 235-36

zyxwv

GaA1As s e e Gallium aluminium arsenide GaAs s e e Gallium arsenide Gain-guided laser diodes (GLD), 123, 124-26 Gallium aluminium arsenide, 126-27, 130, 247 Gallium arsenide, 19, 107-9, 112-15, 127 Genghis Khan, 2, 3 Germanium, 61,134, 136-37, 248, 277 Germany, optical fiber market, 234 Glasgow University, 252 Glass preform in manufacture, 85 GLD s e e Gain-guided laser diodes Graded index fibers, 52, 81-82, 177, 286 Graded index profile, definition, 286 GTE Laboratories, 129

Hansell, Clarence, 14, 276 Hansen, Holger, 14 Hard-clad silica, definition, 286 Hazardous environments and ducted cables, 103-4 Heel, Abraham van, 14 Heliograph, 8-10 Hermaphrodite connector, definition, 286 Hockham, George, 16, 276 Hopkins, Harold Horace, 276 Horizontal cabling for fiber optics, 199-201

Index

Ho:YAG laser, 259 Hybrid cable, definition, 286 Hydrogen losses, definition, 286

311

Integrated Services Digital Networks (ISDN), 233 Intensity (power) modulation of optical transmitters, 67-68 Internal vapour deposition in manufacturing, 85-86 International Standards Organisation (ISO) Standards, 273-75, 287 Internet use of fiber optics, 260 Intrinsic losses, definition, 287 ISDN see Integrated Services Digital Networks ISO see International Standards Organisation Isolator, definition, 287 ITT Corning, 233

zy

zyxwvutsrq

IEC Standards, 268-73 ILD see Index-guided laser diodes ILI see Infonorme London Information Imperial Chemical Industries (ICI), 211 Imperial College of Science and Technology, 276 Incident angle, definition, 287 Index-guided laser diodes (ILD), 124-26 Index matching material, definition, 287 Indium phosphide, 114-16, 128 IndiumGalliumArsenidePhosphide, 114-15, 128, 134, 137, 236 lnfonorme London Information (ILl), 263 Infrared, definition, 287 lnGaAsP see lndiumGalliumArsenidePhosphide Injection laser, definition, 287 Injection luminance, 62 InP see Indium phosphide Insertion loss of connectors, 145, 158-60, 287 Installation of fiber optic cables, 104-5, 204-15 cable selection, 204 ducting, 207 laying, 206-7 minimum bend radius, 209 on power line pylons, 208 storage, 205 vertical risers, 209-10 Institut f6r Festkorperelectronik, Wein, 127 Institution of Electrical Engineers, 16, 276 Institution of Electrical Engineers, Proceedings, 276

Integrated optoelectronics, definition, 287

Jacket, definition, 287 Jane's Defence Weekly, 253

JDS-Uniphase, 235 Jointing/splicing of fibers: acrylic adhesive, 168 advantages and disadvantages of methods, 170 alignment errors during splicing, 171 anaerobic adhesive, 167-68 crimping, 168 cured epoxy, 166-67 cyanoacrylate adhesive, 167 effect of dirt, 165 elastomeric splicer, 173 enclosure design, 179-80 epoxy splice procedure, 166 fusion splicing, 174-79 graded index fibers, 177 multi-fibers, 178-79 procedure, 174-77 single-mode fibers, 178 no epoxy no crimping, 169 pre-injected epoxy, 166 splice losses, 169, 171 UV adhesive, 167, 173-74 V-groove splicer, 172 Jumper cable, definition, 287 Junction laser, definition, 287

312

Index

zyxwvutsrq

Kao, Charles K., 16-17, 276 Kapany, Narinda S., 276 Karbowiak, Antoni E., 276 KD Optics, 220 KDX1000 loss meter, 220 LS20DV LED source, 225 PM23 optical power meter, 225 Keck, Donald, 17, 277 Kessler Marketing Intelligence, 233 Kevlar, 95, 98, 287 Keyance Corporation Japan, 244, 245 Korea, Republic of, 253

medical uses, 258-59 metal clad ridge waveguide (MCRW), 124 microdisks, 128-29 modular lasers, 241-43 modulation, 65-68, 107 multiple signalling, 129-30 noise, 69 optical feedback sensitivity, 126 oxide stripe, 126-27 spatial radiation distribution, 125-26 spectral widths, 124-25 stripe geometry, 126 temperature, 125 threshold currents, 124 vertical cavity surface emitting (VCSEL), 127-28

zyxwvutsr

Lamberton source, 57 Lamm, Heinrich, 14, 276 LAN see Local area network Large core fiber, definition, 287 Larner, David, 251 Laser dazzler, 253-54 Laser diodes: see also Fiber optics; Light emitting diodes; Optoelectronics; Receivers; Technology of fiber optics; Transmitters in 1300 to 1600 nm region, 128 advantages, 119-20 with built-in waveguide, 124 buried heterostructure (BH), 124 and catastrophic optical damage, 114 channelled substrate planer (CSP), 124 comparison with LED, 108, 117, 118 with current-induced waveguide, 123 definition, 287 design and characteristics, 116-19, 122-24 disadvantages, 120-22 distributed feedback laser, 240 double heterostrucure characteristics, 121, 139 gain and index guided diodes compared, 124-26 gain-guided (GLD), 123, 124-26 index-guided (ILD), 124-26 invention of, 15-16 as light source, 19, 62, 106

Laser Focus, 1 6 - 1 7

Laser light sources, 220-21 LaslRvis, 110, 118, 132 Lateral displacement loss, definition, 287 Leak detection using optical fibers, 250 LED see Light emitting diodes Lens couplers, 154 Light, definition, 287 Light emitting diodes: see also Fiber optics; Laser diodes; Optoelectronics; Receivers; Technology of fiber optics; Transmitters advantages in optical fiber systems, 109-10 aluminium gallium arsenide, 113-14 comparison with laser, 108 connecting to an optical fiber, 163 definition, 288 design, 107-10 diffused gallium arsenide, 112-13 edge emitting diode (ELED), 111-12, 119 high radiance, 112 indium phosphide, 114-16 and injection luminance, 62 as light source, 19, 57, 59, 106 modulation, 65-68, 107 preparation, 110-11

Index

Light source, definition, 288 Light waves, definition, 288 Lightguide, definition, 288 LIGHTRAY OFX optical fiber circuit, 244-45 Line terminating unit (LTU), 185-86 Linear modulation of light, 66-67 Link, definition, 288 Lithium niobate, 254-55 Liverpool University, 256 Local area network (LAN), 52, 189, 194, 233, 288 Local government applications for optoelectronics, 256-58 Local loop, definition, 288 Local networks, 184-87 Loffe Physical Institute, St Petersberg, 18 Long distance networks, 187 Long-haul network, definition, 288 Long wavelength, definition, 288 Loose cable type, 95, 99 Loose tube, definition, 288 Loss, definition, 288 Loss measurements for fiber optic systems, 220-21 Losses in optical fiber systems, 196-97, 201-203 Losses in transmission, 53-57 absorption, 53-54 attenuation, 53 bending losses, 55-57 scattering, 54-55 Lucent Technologies, 236, 249

313

glass preform, 85 internal vapour deposition, 85-86 vapour axial deposition, 87 Marconi, 236 Margin, definition, 288 Material dispersion, definition, 288 Material scattering, definition, 288 Maurer, Robert, 17, 277 MBE s e e Molecular beam epitaxy Mechanical splice, definition, 288 MEMS s e e Micro electromechanical systems Metal organic chemical vapour deposition (MOCVD), 127 Metallic armour for ducted cable, 102-3 Metropolitan area network (MAN), 189-90 Micro electromechanical systems (MEMS), 253 Microbending loss in fibers, 56, 288 Mie scattering in fibers, 55 Military applications of fiber optics, 253-56 Mining, uses for fiber optics, 261 Minitel, 184 Misalignment loss, definition, 288 Mixers used with fiber optics, 70-71 MOCVD s e e Metal organic chemical vapour deposition Modal bandwidth, definition, 288 Modal dispersion, definition, 289 Modal noise in multimode fibers, 69-70, 289 Mode: coupling, definition, 289 definition, 289 field diameter, definition, 289 partition noise, 69 stripper, definition, 289 Modes of propagation, 51-53 multimode, graded index, 52 step index, 51 single mode step index, 52-53 Modular lasers, 241-43 Modulation of optical systems, 65-68, 289

zy

zyxwvutsr

Macdonald, Colonel John, 7, 8 Macrobend, definition, 288 Macrobending loss in fibers, 56-57 Magnetic resonance imaging (MRI), 258 MAN s e e Metropolitan area network Manufacturing techniques, 82, 85-91 cap sealing, 90-91 external vapour deposition, 86-87 fiber drawing, 88-89 full length outside deposition (FLOD), 89-90

314

Index

zyxwvutsrq

Molecular beam epitaxi thin film technology, 236 Molecular beam epitaxy (MBE), 127 Muffling, General Freiherr von, 7 Muldex couplers, 74, 186 Multi-core fibers, 243-44 Multimode fiber, 79-82, 289 graded index, 81-82 Multimode fiber design, 79-82 Multiplayer dialectric filter, 73 Multiplexing types, 71-75, 289 dense wavelength division (DWDM), 74, 229 electrical, 72 fiber, 72 time division (TDM), 74-75, 186, 194 wavelength division (WDM), 72-74, 139, 196 Multiport couplers, 154-58 Murray, Reverend Lord George, 3

Office lighting using fiber optics, 256-57 OFL see Optical fault locator On-off modulation of light, 65 Optic connection panel, 55 OpticAir fiberless transmission, 249 Optical: amplifier, definition, 289 bus, 246 cable, definition, 289 computing, 251-52 ether, 249-50 fault locator (OFL), 230-31 fiber, bandwidth, 63-65 colour coding, 97 coupler, definition, 289 definition, 289 frequency response, 64 structure, 49-50 waveguides, 16-17, 18, 289 link, definition, 289 mechanisms in semiconductors, 61-62 multiplexers, 252 power density, 57-58 radio, 250 receiver thermal noise, 69 sensors, 256 signal-to-noise ratio (OSNR), 68-70, 232 switch, definition, 289 telephone, 10, 11 window, definition, 289-90 Optical Fibres Ltd, 211 Optical time domain reflectometer (OTDR), 27, 217, 225-30, 289 advantages and disadvantages, 224, 230-31 compared to optical fault locator, 231 dead zone, 227-28 dynamic range, 228 equipment, 228-30 ghost reflections, 228 test outputs, 226-27 uses, 225-26 Opto-isolators, 252 Optoelectrical converter, defined, 290

zyxwvutsrq

NA see Numerical aperture Nanometre, definition, 289 Napoleon I, Emperor of France, 7, 8 National Institute of Justice (NIJ), 253-54 Nature, 14-15 Nd:YAG laser, 259 Nettest/PK Technology: Model 8000 OTDR, 228 Model CMA4000 OTDR, 229 Network, definition, 289 N e w Electronics, 251

NIJ see National Institute of Justice Nippon Telegraph and Telephone (NTT), 237, 277 Norris, John, 2 Nortel, 235 Noynes: visual fault finder, 222 WSP 100 Multi-wavelength Selective Power Meter, 231-32 NTT see Nippon Telegraph and Telephone Numerical aperture (acceptance angle), 48-49, 50, 289

zy zyxwvu Index

Optoelectronic switches, 252-53 Optoelectronics:see a l s o Couplers; Fiber optics; Laser diodes; Light emitting diodes; Receivers; Technology of fiber optics; Transmitters; all-optical network, 33 basic theory, 36-75 acceptance angle, 48-49 acceptance cone, 47-48 angle of incidence, 45 bandwidth, 62-65 critical angle, 46-47 dispersion losses see Dispersion losses in fibers fiber structure, 49-50 losses s e e Losses in transmission mixers, 70-71 modes s e e Modes of propagation modulation, 65-68 multiplexing s e e Multiplexing types numerical aperture, 49 optical power density, 57-58 optical signal-to-noise ratio (OSNR), 68-70, 232 reflection and refraction, 36-39, 42-45 refractive index, 39-40 semiconductors, 61-62 Snell' s Law, 41-43 total internal reflection (TIR), 13-15, 40-45, 50 in communication networks, 33 definition, 289 early signalling devices, 2, 7 in the future, 33-35 local government applications, 256-58 practical applications, 32-33 OSNR see Optical signal-to-noise ratio OTDR see Optical time domain reflectometer

Passive coupler, definition, 290 Patch panels (distribution frames), 201,210-11,290

315

Patchcord, definition, 290 PCM s e e Pulse code modulation PDFFA s e e Praseodymium-doped fluoride fiber amplifier Peak wavelength, definition, 290 Peltier coooler, 242, 247 Persenick, Dr Stuart, 225 PET see Position emission tomography Phase modulation, definition, 290 Photocurrent, definition, 290 Photodetector, 22, 23, 290 Photodiode, 62 definition, 290 design, 132-34 Photon, definition, 290 Photonics, definition, 290 Photophone, 11-13, 276 Pigtail, definition, 290 PIN photodiode, 132, 134-35, 139, 240, 248, 290 Planar waveguide, definition, 290 Plastic-clad silica fiber (PCS), 290 Plastic optical fiber (POF), 91-92, 290 Plastic opto-chips, 254-55 Plenum, defined, 291 PMMA s e e Polymethylmethacrylate POF s e e Plastic optical fiber Point-to-point, defined, 291 Polarization of light in fiber optics, 238, 291 Polarization stability, defined, 291 Polishing, defined, 291 Polybius, 2 Polymethylmethacrylate (PMMA), 91 Polytetrafluoroethylene (PTFE) (Teflon), 88 Porous silicon, 237 Position emission tomography (PET), 258 Power and attenuation measurement, 221,223-24 Power budget, defined, 291 Power meter, defined, 291 Praseodymium-doped fluoride fiber amplifier (PDFFA), 141 Pre-injected epoxy for jointing fibers, 166

316

Index

zyxwvutsrq

zyxwvutsrq

Preform, defined, 291 Prefusing, defined, 291 Primary coating, defined, 291 PTFE s e e polytetrafluoroethylene Ptolemy, Claudius, 36, 37 Pulse code modulation (PCM), 187, 291 Pulse dispersion, defined, 291 Pulse spreading, defined, 291

QA Photos Ltd, 24 Quantum efficiency, 112, 114, 291 Quantum noise of light, 69 Quaternary, defined, 291

Radiance, defined, 291 Radiation pattern, defined, 291 Rare earth doped optical fibers, 90, 240-41 Rayleigh backscattering, 30-31, 54-55, 225, 226, 227, 291 Receivers, 132-40, 291: see also Couplers; Fiber optics; Laser diodes; Light emitting diodes; Technology of fiber optics; Transmitters additional stages, 138 amplifier design, 138-41 analog fibre optic, 137 converting light into electrical energy, 132-34 detector composition and wavelength, 134 digital fibre optic, 137-38 erbium doped, fiber amplifier (EDFA), 139-40, 236 fluoride fiber amplifier (EDFFA), 140 tellurite fiber amplifier (EDTFA), 140-41 laser amplifier repeater, 139 photodiode design, 132-34 avalanche (APD), 132, 135 germanium, 136-37 indium gallium arsenide, 137

PIN, 132, 134-35, 139 silicon, 135-37 praseodymium-doped fluoride fiber amplifier (PDFFA), 141 semiconductor optical amplifier, 141 Reeves, Alec, 276 Reflectance, definition, 292 Reflection and refraction, 36-39, 42-45 Refraction of light, 37-38, 292 Refractive index (RI), 39-40, 51-52, 292 Repeator and regenerator spacing, 180-82, 292 RI see Refractive Index Ribbon cable, definition, 292 Ring network, definition, 292 Rise time, definition, 292 Riser, definition, 292 Road signs using fiber optics, 257-58 Rodent protection of ducted cable, 101-102 Roth and Reuss, Vienna, 13 Routing of optical fiber cables, 197-201 campus cabling, 197-99 distribution frames, 201 fiber to the customer, 198 horizontal cabling, 199-201 centralised, 200-201 conventional, 199-200 installation see Installation of fiber optic cables riser area cabling, 199 Royal Corps of Signals, 3, 4, 5, 8, 9

Saint-Ren6, Henry, 13 Sanyo Semiconductor Corporation, 129-30 Scattering, definition, 292 Schultz, Peter, 17, 277 SDI Research, 251 Semiconductor optical amplifier, 141, 292 Semiconductors in optoelectronics, 61-62 Sensitivity, definition, 292

Index 317

Serial transmission, definition, 292 Sheath, definition, 292 Short wavelength, definition, 292 Shot noise, definition, 292 Sifam Fiber Optics, 235 Signal-to-noise ratio of transmission systems, 68-70, 292 Silica glass, definition, 292 Silicon, 61, 134, 135-36 Simplex, definition, 292 Single-mode fiber, 77-79, 293 SLB s e e System loss budget Slotted core cables, 95-97 SMA s e e Sub multiple assembly connectors Smith, David, 13 Snell, Willebrord van Roijen, 41-42 Snell's Law, 41-43 Solitron pulses in fiber optics, 238-39, 293 SONET see Synchronous optical network Source, definition, 293 Southampton Photonics, 236, 240, 243 Southampton University Optoelectronics Research Centre, 236 Spectral attenuation, definition, 293 Spectral bandwidth, definition, 293 Speed of light, definition, 293 Splice losses in jointing fibers, 169, 171,293 Splicing see Jointing/splicing Standard Telecommunications Laboratories (STL), 16-17, 276 Standard Telephone & Cable (STC), 149 Standards: EN, 263-67 IEC, 268-73 ISO, 273-75 Star network, definition, 293 Station, definition, 293 STC s e e Standard Telephone & Cable Step index, 51, 52-53, 79-81,293 Steradian, 57 Stick and turn connectors (ST), 147, 148

zy

STL

s e e Standard Telecommunications Laboratories Strain member, definition, 293 Strength member, definition, 293 Stripping, definition, 293 Sub multiple assembly connectors (SMA), 145, 148 Subscriber loop, definition, 294 Super lattice thin film technology, 236 Surface emitting diode, definition, 294 Synchronous optical network (SONET), 238 Synchronous transmission, definition, 294 System loss budget (SLB), 201-203, 288

zyxwvutsrq T-type telegraph, 5, 6 Tainter, Sununer, 10 Tap loss, definition, 294 TDM s e e Time division multiplexing Technical University of Delft, 14 Technology of fiber optics, 76-105: s e e a l s o Couplers; Jointing/splicing of fibers; Laser diodes; Light emitting diodes; Receivers; Transmitters; basic design, 76-77 cable characteristics, 92-95 bending diameter, 92-93 buffer tube, 93-95 deflecting diameter, 92-93 tensile strength, 93 cable construction, 98-99 cable ducts, 97 cable types, 95-97 loose, 95, 99 slotted core, 95-97 tight buffered, 95 claddings, advantages and disadvantages, 92 comparisons of types of fiber, 83, 84 ducted cable, 99-104 external, 99 for hazardous environments, 103-4 installation, 104-5

318

Index

zyxwvutsrq zyxwvut

Technology of fiber optics ( c o n t . ) ducted cable ( c o n t . ) metallic armour, 102-3 rodent protection, 101-102 universal, 100 universal ruggedised, 100 water protection, 101 jointing see Jointing/splicing Tee coupler, definition, 294 Teflon see polytetrafluoroethylene (PTFE) Telecommunication systems, defined, 294 Telephone networks, 187-88 Temperature monitor using optical fiber, 251 Tensile strength of cables, 93 Ternary, defined, 294 Testing optoelectronics, 215-32 equipment, 221-32 bandwidth measurement, 231-32 defined, 294 fiber optic tracers, 221-23 field testers, 224-25 laser light sources, 220-21 loss measurements, 220-21 optical fault locator (OFL), 230-31 OTDR see Optical time domain reflectometer power and attenuation measurement, 223-24 power meters, 221 installation and field tests, 218-19 during manufacture, 215-18 attenuation, 217 bandwidth, 217 physical characteristics, 215-16 Thermal noise, defined, 294 Thermal stability, defined, 294 Thermistor, 242 Threshold current, defined, 294 Throughput loss, defined, 294 Tight buffered cables, 95, 294 Time division multiplexing (TDM), 74-75, 186, 194, 294 Time Warner Telecom, 260 TIR see Total internal reflection

Token, defined, 294 Total internal reflection (TIR), 13-15, 40-45, 50, 294 Transceiver, defined, 295 Transducer, defined, 295 Transmission loss, defined, 295 Transmission media, defined, 295 Transmissive mixer, 71 Transmitters, 106-30, 295: see also Fiber optics; Laser diodes; Light emitting diodes; Receivers laser diodes, in 1300 to 1600 nm region, 128 advantages, 119-20 with built-in waveguide, 124 buried heterostructure (BH), 124 and catastrophic optical damage, 114 channelled substrate planer (CSP), 124 comparison with LED, 108, 117, 118 with current-induced waveguide, 123 design and characteristics, 116-19, 122-24 disadvantages, 120-22 double heterostrucure characteristics, 121, 139 gain and index guided diodes compared, 124-26 gain-guided (GLD), 123, 124-26 index-guided (ILD), 124-26 invention of, 15-16 as light source, 19, 62, 106 metal clad ridge waveguide (MCRW), 124 microdisks, 128-29 modulation, 65-68, 107 multiple signalling, 129-30 noise, 69 optical feedback sensitivity, 126 oxide stripe, 126-27 spatial radiation distribution, 125-26 spectral widths, 124-25 stripe geometry, 126 temperature, 125

Index

threshold currents, 124 vertical cavity surface emitting (VCSEL), 127-28 light emitting diode (LED), advantages in optical fiber systems, 109-10 aluminium gallium arsenide, 113-14 comparison with laser, 108 design, 107-10 diffused gallium arsenide, 112-13 edge emitting diode (ELED), 111-12, 119 high radiance, 112 indium phosphide, 114-16 and injection luminance, 62 as light source, 19, 57, 59, 106 modulation, 65-68, 107 preparation, 110-11 Transparency, defined, 295 Tree coupler, defined, 295 Tunable lasers in fiber optics, 240 Turbotest 400 (Noynes), 223 Tyco Electronics, 244 Tyndall, John, 10, 11,276

UK Advisory Council on Science and Technology (ACOST), 233 UK market in fiber optics, 235-36 Ultraviolet, defined, 295 Uniformity, defined, 295 United Kingdom, optical fiber market, 235 Universal (ruggedised) ducted cable, 100 University of New South Wales, 276 University of Southern California, 254 University of Washington, 254 U.S. Army Research Office, 237

319

zy

U.S. Defence Advanced Research Projects Agency (DARPA), 253-54 UV adhesive, 167, 173-74 V-groove splicer, 172 Vanzetti Systems, 251 Vapour axial deposition in manufacturing, 87 Vertical cavity surface emitting laser diodes(VCSEL), 127-28 Videophone, defined, 295 Virtual reality, defined, 295 Virtually lossless network (VLON), 246 Visible light, defined, 295

zyxwv

WAN s e e Wide area network Water protection of ducted cable, 101 Waveguide fiber, 16-17, 18, 295 Wavelength, defined, 295 Wavelength division multiplexing (WDM), 72-74, 139, 196, 235, 246, 254, 295 Wheeler, William, 13, 276 Whiteman Controls Corporation, 250 Wide area network (WAN), 190-91, 194, 295 Worcester, Marquis of, 2, 3 Working margin, defined, 295 Xerox Corporation, 189 Ytterbium, 140 Zheleg, Kathy, 249

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