Understanding Optical CommunicationsHarry J. R. Dutton                     International Technical Support Organization   ...
SG24-5230-00International Technical Support OrganizationUnderstanding Optical CommunicationsSeptember 1998
Take Note!  Before using this information and the product it supports, be sure to read the general information in Appendix...
Contents                             Figures     . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ....
3.1.1 Spontaneous Emission . . . . . . . . . . . . . . . .            . . . . . . . . . . .    81                         ...
5.3 Second Harmonic Generation (SHG) . . . . . . . . . . . .               . . . . . . . . .     184                  5.4 ...
7.1 Point-to-Point Transmission Systems          . . . . . . . . . .   . . . . . . . . . .   297                          ...
8.2.2 Ethernet on Fibre . . . . . . . . . . . . . . . . . .       . . . . . . . . . . .    368   8.2.3 CSMA/CD Performance...
9.4.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .        451                          9.5 ...
12.4.2 Code Division Multiple Access (CDMA)               . . . . . . . . . . . . . . . .    528  12.4.3 Practical Optical...
x   Understanding Optical Communications
Figures                              1.   Optical Transmission - Schematic . . . . . . . . . . . . . . . . .         . . ....
51.    HPCF Structure . . . . . . . . . . . . . . . . . . . . . . . . . . .        . . . . . .    76                      ...
105.   Travelling Wave Photodector - Principle . . . . . . . . . . . . . .            . . . .   144106.   Resonant-Cavity ...
159.   GRIN Lens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .       . . .   205                        ...
213.   MZI Add-Drop Device . . . . . . . . . . . . . . . . . . . . . .         . . . . . . .    247214.   Acoustic Modulat...
267.   Spectral Inverter - Schematic      . . . . . . . . . . . . . . . . . . . .   . . . .   333                         ...
321.   Add-Drop Multiplexor Using FBG and Circulators . . . . . . . . . . . .             .   425322.   Filter Using Casca...
375.   Optical TDM Configuration . . . . . . . . . . . . . . . . . . .          . . . . . . .   533                       ...
Tables                              1.   Bandgap Energy and Possible Wavelength Ranges in              Various Materials  ...
xx   Understanding Optical Communications
Preface                             This book presents a high level technical overview of the emerging technologies of    ...
Acknowledgments                         This book was written as a project of the IBM International Technical Support     ...
Part 1. Theory and Devices© Copyright IBM Corp. 1998                            1
2   Understanding Optical Communications
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Sg245230
Upcoming SlideShare
Loading in...5
×

Sg245230

1,460

Published on

Published in: Business, Technology
0 Comments
1 Like
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total Views
1,460
On Slideshare
0
From Embeds
0
Number of Embeds
1
Actions
Shares
0
Downloads
29
Comments
0
Likes
1
Embeds 0
No embeds

No notes for slide

Transcript of "Sg245230"

  1. 1. Understanding Optical CommunicationsHarry J. R. Dutton International Technical Support Organization http://www.redbooks.ibm.com SG24-5230-00
  2. 2. SG24-5230-00International Technical Support OrganizationUnderstanding Optical CommunicationsSeptember 1998
  3. 3. Take Note! Before using this information and the product it supports, be sure to read the general information in Appendix F, “Special Notices” on page 591.First Edition (September 1998)This edition applies to fibre optic communications and optical networking.Comments may be addressed to:IBM Corporation, International Technical Support OrganizationDept. HZ8 Building 678P.O. Box 12195Research Triangle Park, NC 27709-2195When you send information to IBM, you grant IBM a non-exclusive right to use or distribute the information in any way it believesappropriate without incurring any obligation to you.© Copyright International Business Machines Corporation 1998. All rights reserved.Note to U.S. Government Users — Documentation related to restricted rights — Use, duplication or disclosure is subject torestrictions set forth in GSA ADP Schedule Contract with IBM Corp.
  4. 4. Contents Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xix Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxi About the Author . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxi By the Same Author . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxi Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxii Comments Welcome . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxiiPart 1. Theory and Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Chapter 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1.1 Optical Transmission System Concepts . . . . . . . . . . . . . . . . . . 4 1.1.2 Optical Networking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 1.1.3 Optical Interconnects . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 1.1.4 Optical Computers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 1.1.5 Further Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Chapter 2. Optical Fibre . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2.1 The Nature of Light . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2.1.1 Light as an Electromagnetic Wave . . . . . . . . . . . . . . . . . . . . 16 2.1.2 Polarisation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 2.1.3 Interference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 2.2 Transmitting Light on a Fibre . . . . . . . . . . . . . . . . . . . . . . . . . . 25 2.2.1 Characteristics of Glasses . . . . . . . . . . . . . . . . . . . . . . . . . 29 2.2.2 Transmission Capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 2.2.3 Operational Principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 2.2.4 Fibre Refractive Index Profiles . . . . . . . . . . . . . . . . . . . . . . . 36 2.3 Light Propagation in Multimode Fibre . . . . . . . . . . . . . . . . . . . . . 39 2.3.1 Snells Law . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 2.3.2 Critical Angle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 2.3.3 Numerical Aperture (NA) . . . . . . . . . . . . . . . . . . . . . . . . . . 42 2.3.4 Propagation Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 2.3.5 Mode Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 2.3.6 Modal Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 2.3.7 Naming Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 2.4 Single-Mode Propagation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 2.4.1 Single-Mode Characteristics . . . . . . . . . . . . . . . . . . . . . . . . 57 2.4.2 Dispersion in Single-Mode Fibre . . . . . . . . . . . . . . . . . . . . . . 59 2.4.3 Mode Partition Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 2.4.4 Reflections and Return Loss Variation . . . . . . . . . . . . . . . . . . 67 2.4.5 Non-Linear High-Power Effects . . . . . . . . . . . . . . . . . . . . . . 69 2.5 Plastic Optical Fibre (POF) . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 2.5.1 POF Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 2.6 Hard Polymer (plastic) Clad (silica) Fibre (HPCF) . . . . . . . . . . . . . . 76 Chapter 3. Optical Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 3.1 Light Production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79© Copyright IBM Corp. 1998 iii
  5. 5. 3.1.1 Spontaneous Emission . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 3.2 Light Emitting Diodes (LEDs) . . . . . . . . . . . . . . . . . . . . . . . . . . 82 3.2.1 The Semiconductor Junction Diode . . . . . . . . . . . . . . . . . . . . 82 3.2.2 Construction and Operation of LEDs . . . . . . . . . . . . . . . . . . . 84 3.2.3 Heterojunctions (Practical LEDs) . . . . . . . . . . . . . . . . . . . . . 86 3.2.4 Characteristics of LEDs . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 3.3 Lasers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 3.3.1 Principle of the LASER . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 3.3.2 Semiconductor Laser Diodes . . . . . . . . . . . . . . . . . . . . . . . 101 3.3.3 Fabry-Perot Lasers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 3.3.4 Distributed Feedback (DFB) Lasers . . . . . . . . . . . . . . . . . . . 113 3.3.5 Integrated Absorption Modulators . . . . . . . . . . . . . . . . . . . . 116 3.3.6 Q-Switching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 3.3.7 Mode-Locking and Self-Pulsating Lasers . . . . . . . . . . . . . . . . 117 3.3.8 Distributed Bragg Reflector (DBR) Lasers . . . . . . . . . . . . . . . 118 3.3.9 Quantum Wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 3.3.10 Tunable DBR Lasers . . . . . . . . . . . . . . . . . . . . . . . . . . 120 3.3.11 External Cavity DBR Lasers . . . . . . . . . . . . . . . . . . . . . . 123 3.3.12 External Fibre-Cavity DBR Lasers . . . . . . . . . . . . . . . . . . . 124 3.3.13 Multi-Wavelength Lasers . . . . . . . . . . . . . . . . . . . . . . . . 125 3.3.14 Vertical Cavity Surface Emitting Lasers (VCSELs) . . . . . . . . . 125 3.3.15 In-Fibre Lasers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 3.3.16 Fibre Ring Lasers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129 3.3.17 Upconversion Fibre Lasers (Double Pumping) . . . . . . . . . . . . 130 3.3.18 Gas Lasers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 3.3.19 Free Electron Lasers (FELs) . . . . . . . . . . . . . . . . . . . . . . 132 3.4 Further Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 Chapter 4. Optical Detectors . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 4.1 Photoconductors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 4.2 Photodiodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 4.2.1 P-N Diodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 4.2.2 P-I-N Diodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 4.2.3 Schottky-Barrier Photodiodes . . . . . . . . . . . . . . . . . . . . . . 138 4.2.4 Avalanche Photodiodes (APDs) . . . . . . . . . . . . . . . . . . . . . 139 4.2.5 Hetero-Interface Photodetectors . . . . . . . . . . . . . . . . . . . . . 143 4.2.6 Travelling-Wave Photodetectors . . . . . . . . . . . . . . . . . . . . . 143 4.2.7 Resonant-Cavity Photodetectors . . . . . . . . . . . . . . . . . . . . . 145 4.3 Phototransistors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146 4.4 Further Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147 Chapter 5. Optical Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 5.1 Optical Component Technologies . . . . . . . . . . . . . . . . . . . . . . . 149 5.1.1 Planar Optical Devices . . . . . . . . . . . . . . . . . . . . . . . . . . 150 5.1.2 Fabrication of Planar Optical Devices . . . . . . . . . . . . . . . . . . 152 5.1.3 Integrated Optical Circuits (Planar Assemblies) . . . . . . . . . . . . 155 5.2 Optical Amplifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 5.2.1 Erbium Doped Fibre Amplifiers (EDFAs) . . . . . . . . . . . . . . . . 159 5.2.2 Praseodymium (Pr) Doped Fibre Amplifiers . . . . . . . . . . . . . . 177 5.2.3 Neodymium (Nd) Doped Fibre Amplifiers . . . . . . . . . . . . . . . . 178 5.2.4 Plastic Fibre Amplifiers . . . . . . . . . . . . . . . . . . . . . . . . . . 178 5.2.5 Erbium Doped Planar Devices . . . . . . . . . . . . . . . . . . . . . . 179 5.2.6 Semiconductor Optical/Laser Amplifiers (SOAs/SLAs) . . . . . . . . 180 5.2.7 Raman Effect Amplifiers . . . . . . . . . . . . . . . . . . . . . . . . . 182iv Understanding Optical Communications
  6. 6. 5.3 Second Harmonic Generation (SHG) . . . . . . . . . . . . . . . . . . . . . 184 5.4 Splitters and Couplers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 5.4.1 Resonant Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186 5.4.2 “Y” Couplers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193 5.4.3 Star Couplers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193 5.4.4 Beamsplitter Prisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196 5.4.5 Isolators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198 5.4.6 Circulators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200 5.5 Polarisation Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204 5.5.1 Fibre Loop Polarisation Controller . . . . . . . . . . . . . . . . . . . . 204 5.5.2 Fibre Squeezer Polarisation Controller . . . . . . . . . . . . . . . . . 205 5.6 Lenses and Prisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205 5.6.1 Graded Index (GRIN) Lenses . . . . . . . . . . . . . . . . . . . . . . 205 5.7 Diffraction Gratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206 5.7.1 Planar Diffraction Gratings . . . . . . . . . . . . . . . . . . . . . . . . 206 5.7.2 In-Fibre Bragg Gratings (FBGs) . . . . . . . . . . . . . . . . . . . . . 211 5.7.3 Waveguide Grating Routers (WGRs) . . . . . . . . . . . . . . . . . . 222 5.8 Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227 5.8.2 Fabry-Perot Filter (Etalon) . . . . . . . . . . . . . . . . . . . . . . . . 229 5.8.3 In-Fibre Bragg Grating Filters . . . . . . . . . . . . . . . . . . . . . . 234 5.8.4 Fibre Ring Resonators . . . . . . . . . . . . . . . . . . . . . . . . . . 235 5.8.5 Dielectric Filters for WDM Multiplexing/Demultiplexing . . . . . . . . 237 5.9 Modulators and Switches . . . . . . . . . . . . . . . . . . . . . . . . . . . 238 5.9.1 Switches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 5.9.2 Optical Switching Elements . . . . . . . . . . . . . . . . . . . . . . . 239 5.9.3 Optically Controlled Switches . . . . . . . . . . . . . . . . . . . . . . 242 5.9.4 Electro-Absorption Modulators . . . . . . . . . . . . . . . . . . . . . . 248 5.9.5 Acoustic Modulators . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249 5.9.6 Acoustooptic Tunable Filters (AOTFs) . . . . . . . . . . . . . . . . . 252 5.9.7 Phase Modulators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255 5.9.8 Modulation Using a Mach-Zehnder Interferometer . . . . . . . . . . 256 5.9.9 Pockels Cell Modulators . . . . . . . . . . . . . . . . . . . . . . . . . 258 5.9.10 Faraday Effect Modulators . . . . . . . . . . . . . . . . . . . . . . . 260 5.10 Repeaters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261 5.11 Further Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262 Chapter 6. Fibre Manufacture, Cables and Connectors . . . . . . . . . . 267 6.1 The Technology of Fibre Manufacture . . . . . . . . . . . . . . . . . . . . 267 6.1.1 Purifying Silica . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267 6.1.2 Drawing the Fibre . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268 6.1.3 The Double-Crucible Method . . . . . . . . . . . . . . . . . . . . . . . 270 6.1.4 Vapour Deposition Techniques . . . . . . . . . . . . . . . . . . . . . 271 6.2 Joining Fibres . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275 6.2.1 Fusion Splicing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276 6.2.2 Mechanical Splicing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278 6.2.3 Mechanical Splicing with Alignment and Bonding . . . . . . . . . . . 279 6.2.4 Losses in Fibre Joins . . . . . . . . . . . . . . . . . . . . . . . . . . . 279 6.2.5 Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283 6.3 Fibre Cables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285Part 2. Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295 Chapter 7. Optical Communication Systems . . . . . . . . . . . . . . . . . 297 Contents v
  7. 7. 7.1 Point-to-Point Transmission Systems . . . . . . . . . . . . . . . . . . . . 297 7.1.1 Traditional Single-Channel Systems . . . . . . . . . . . . . . . . . . 297 7.1.2 Amplified Single-Channel Systems . . . . . . . . . . . . . . . . . . . 299 7.1.3 WDM Systems Overview . . . . . . . . . . . . . . . . . . . . . . . . . 300 7.2 Modulation (Making the Light Carry a Signal) . . . . . . . . . . . . . . . . 301 7.2.1 On-Off Keying (OOK) . . . . . . . . . . . . . . . . . . . . . . . . . . . 301 7.2.2 Multi-State Coding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306 7.2.3 Forward Error Correction (FEC) . . . . . . . . . . . . . . . . . . . . . 308 7.2.4 Receiving the Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . 309 7.2.5 Timing Recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310 7.2.6 Bandwidth Occupancy . . . . . . . . . . . . . . . . . . . . . . . . . . 312 7.2.7 Analogue Amplitude Modulation (Continuous Wave) . . . . . . . . . 313 7.2.8 Frequency Shift Keying (FSK) . . . . . . . . . . . . . . . . . . . . . . 313 7.2.9 Phase Shift Keying (PSK) . . . . . . . . . . . . . . . . . . . . . . . . 314 7.2.10 Polarity Modulation (PolSK) . . . . . . . . . . . . . . . . . . . . . . . 314 7.2.11 Directional Transmission . . . . . . . . . . . . . . . . . . . . . . . . 314 7.2.12 Character Coding . . . . . . . . . . . . . . . . . . . . . . . . . . . . 314 7.3 Transmission System Limits and Characteristics . . . . . . . . . . . . . . 316 7.4 Optical System Engineering . . . . . . . . . . . . . . . . . . . . . . . . . . 317 7.4.1 System Power Budgeting . . . . . . . . . . . . . . . . . . . . . . . . . 317 7.4.2 Laser Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322 7.4.3 Is There a Speed Limit? . . . . . . . . . . . . . . . . . . . . . . . . . 323 7.4.4 Reflections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325 7.4.5 Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326 7.4.6 Bit Error Rates (BER) . . . . . . . . . . . . . . . . . . . . . . . . . . . 327 7.5 Control of Dispersion in Single-Mode Fibre Links . . . . . . . . . . . . . . 328 7.5.1 Control of Spectral Width . . . . . . . . . . . . . . . . . . . . . . . . . 329 7.5.2 Dispersion Shifted Fibre . . . . . . . . . . . . . . . . . . . . . . . . . 330 7.5.3 Dispersion Compensating Fibre . . . . . . . . . . . . . . . . . . . . . 330 7.5.4 Balancing Dispersion on a Link . . . . . . . . . . . . . . . . . . . . . 332 7.5.5 Mid-Span Spectral Inversion . . . . . . . . . . . . . . . . . . . . . . . 332 7.5.6 Chirped Fibre Bragg Gratings . . . . . . . . . . . . . . . . . . . . . . 334 7.6 Control of Dispersion in Multimode Fibre . . . . . . . . . . . . . . . . . . 335 7.6.1 Maximum Propagation Distance on Multimode Fibre . . . . . . . . . 335 7.6.2 Light Sources for Multimode Systems . . . . . . . . . . . . . . . . . 337 7.7 Fibre Optics in Different Environments . . . . . . . . . . . . . . . . . . . . 340 7.8 Test Equipment and Techniques . . . . . . . . . . . . . . . . . . . . . . . 342 7.8.1 Optical Power Meters (Optical Multimeter) . . . . . . . . . . . . . . . 342 7.8.2 Optical Time-Domain Reflectometers (OTDRs) . . . . . . . . . . . . 343 7.8.3 Spectrum Analysers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345 7.8.4 Eye Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347 7.9 Further Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349 Chapter 8. Optical Link Connections in Electronic Networks . . . . . . . 351 8.1 Fibre Distributed Data Interface (FDDI) . . . . . . . . . . . . . . . . . . . 353 8.1.1 Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354 8.1.2 Access Protocol Operation . . . . . . . . . . . . . . . . . . . . . . . . 356 8.1.3 Ring Initialisation, Monitoring and Error Handling . . . . . . . . . . . 357 8.1.4 Physical Media . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357 8.1.5 Physical Layer Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . 358 8.1.6 Node Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 364 8.1.7 High-Speed Performance . . . . . . . . . . . . . . . . . . . . . . . . . 365 8.2 Ethernet (IEEE 802.3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366 8.2.1 Principles of Ethernet . . . . . . . . . . . . . . . . . . . . . . . . . . . 366vi Understanding Optical Communications
  8. 8. 8.2.2 Ethernet on Fibre . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 368 8.2.3 CSMA/CD Performance . . . . . . . . . . . . . . . . . . . . . . . . . . 369 8.2.4 High Speed or “Fast” (100 Mbps) Ethernet (HSE) . . . . . . . . . . 371 8.2.5 Gigabit Ethernet (GbE) . . . . . . . . . . . . . . . . . . . . . . . . . . 3728.3 Fibre Channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375 8.3.1 Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375 8.3.2 Physical Media . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376 8.3.3 Transmission Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . 378 8.3.4 Signalling Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 378 8.3.5 Open Fibre Control (OFC) Safety System . . . . . . . . . . . . . . . 3808.4 ESCON and Inter-System Coupling (ISC) . . . . . . . . . . . . . . . . . . 381 8.4.2 Inter-System Coupling (ISC) Feature . . . . . . . . . . . . . . . . . . 3858.5 OptiConnect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 386 8.5.1 OptiConnect Optical Specifications . . . . . . . . . . . . . . . . . . . 3878.6 Synchronous Optical Network (SONET) and SDH . . . . . . . . . . . . . 387 8.6.1 Sonet Protocol Structure . . . . . . . . . . . . . . . . . . . . . . . . . 389 8.6.2 Synchronous Digital Hierarchy (SDH) . . . . . . . . . . . . . . . . . . 391 8.6.3 Tributaries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 392 8.6.4 Sonet/SDH Line Speeds and Signals . . . . . . . . . . . . . . . . . . 392 8.6.5 Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393 8.6.6 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393 8.6.7 Sonet Rings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393 8.6.8 Plesiochronous Digital Hierarchy . . . . . . . . . . . . . . . . . . . . 3948.7 Asynchronous Transfer Mode (ATM) . . . . . . . . . . . . . . . . . . . . . 395 8.7.1 High-Speed Technology . . . . . . . . . . . . . . . . . . . . . . . . . 396 8.7.2 ATM Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 397 8.7.3 The Structure of an ATM Network . . . . . . . . . . . . . . . . . . . . 399 8.7.4 Physical Link Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . 404 8.7.5 Network Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . 406 8.7.6 Transporting Information in an ATM Network . . . . . . . . . . . . . 4078.8 Further Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 409Chapter 9. Wavelength Division Multiplexing . . . . . . . . . . . . . . . . 411 9.1.1 Simple (Sparse) WDM . . . . . . . . . . . . . . . . . . . . . . . . . . 411 9.1.2 Dense WDM Links . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412 9.1.3 Using Dense and Sparse WDM Together - An Example . . . . . . . 413 9.1.4 Building Photonic Networks - Technical Challenges . . . . . . . . . 4149.2 Components for WDM Systems . . . . . . . . . . . . . . . . . . . . . . . . 415 9.2.1 Light Sources for WDM . . . . . . . . . . . . . . . . . . . . . . . . . . 415 9.2.2 Multiplexing (Combining) the Light . . . . . . . . . . . . . . . . . . . 419 9.2.3 Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 420 9.2.4 Demultiplexing the Light . . . . . . . . . . . . . . . . . . . . . . . . . 420 9.2.5 Add-Drop Multiplexors . . . . . . . . . . . . . . . . . . . . . . . . . . 424 9.2.6 Optical Space-Division Switches . . . . . . . . . . . . . . . . . . . . . 428 9.2.7 Optical Switching Nodes . . . . . . . . . . . . . . . . . . . . . . . . . 429 9.2.8 Wavelength Converters . . . . . . . . . . . . . . . . . . . . . . . . . . 4319.3 Standards for WDM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4369.4 Systems Engineering in the WDM Environment . . . . . . . . . . . . . . 437 9.4.1 Fitting the Signal into Its Allocated Waveband . . . . . . . . . . . . . 438 9.4.2 Stabilising Wavelengths . . . . . . . . . . . . . . . . . . . . . . . . . . 441 9.4.3 Controlling Non-linear Effects . . . . . . . . . . . . . . . . . . . . . . 442 9.4.4 Control of Dispersion in WDM Systems . . . . . . . . . . . . . . . . 445 9.4.5 Amplifier Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 445 9.4.6 Noise in WDM Systems . . . . . . . . . . . . . . . . . . . . . . . . . . 449 Contents vii
  9. 9. 9.4.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 451 9.5 Further Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 453 Chapter 10. Lightwave Networks . . . . . . . . . . . . . . . . . . . . . . . . 455 10.1.1 Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 456 10.1.2 Optical Network Technologies . . . . . . . . . . . . . . . . . . . . . 458 10.1.3 Sharing the Fibre . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 459 10.1.4 Modes of Data Transfer . . . . . . . . . . . . . . . . . . . . . . . . . 461 10.1.5 Network Topologies for the MAN or WAN . . . . . . . . . . . . . . 462 10.2 WDM for LANs (and Small MANs) . . . . . . . . . . . . . . . . . . . . . 468 10.2.1 Network Topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . 468 10.2.2 Transmission System Design . . . . . . . . . . . . . . . . . . . . . . 471 10.2.3 Access Protocols for the Shared Medium . . . . . . . . . . . . . . . 472 10.3 Some Possible Systems Approaches . . . . . . . . . . . . . . . . . . . . 476 10.3.1 Centralised WDM Circuit Switch . . . . . . . . . . . . . . . . . . . . 476 10.3.2 Multichannel CSMA/CD . . . . . . . . . . . . . . . . . . . . . . . . . 477 10.3.3 Coordination on a Control Channel . . . . . . . . . . . . . . . . . . 478 10.3.4 Code Division Multiple Access (CDMA) . . . . . . . . . . . . . . . . 479 10.3.5 Experimental Systems . . . . . . . . . . . . . . . . . . . . . . . . . . 479 10.3.6 Metropolitan Area Add/Drop WDM with a Multiwavelength Source 482 10.4 WDM Research Demonstrators . . . . . . . . . . . . . . . . . . . . . . . 484 10.5 The IBM 9729 - A WDM System for the Metropolitan Area Network . . 486 10.5.1 9729 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 486 10.5.2 Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 488 10.5.3 Grating Assembly (9729) . . . . . . . . . . . . . . . . . . . . . . . . 492 10.5.4 Laser/Receiver Cards (LRC) . . . . . . . . . . . . . . . . . . . . . . 493 10.5.5 I/O Cards (IOC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 494 10.5.6 Dual Fibre Switching Feature . . . . . . . . . . . . . . . . . . . . . . 495 10.5.7 System Engineering Considerations . . . . . . . . . . . . . . . . . . 495 10.5.8 Network Management . . . . . . . . . . . . . . . . . . . . . . . . . . 499 10.5.9 Systems Potential . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500 10.6 Architecture of a First-Generation WDM for the WAN . . . . . . . . . . 502 10.7 Further Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 505 Chapter 11. Fibre In The (Local) Loop - FITL . . . . . . . . . . . . . . . . . 507 11.1.1 System Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . 507 11.1.2 The Existing Telephone Network . . . . . . . . . . . . . . . . . . . . 509 11.1.3 Cable Television Networks . . . . . . . . . . . . . . . . . . . . . . . 510 11.1.4 Hybrid Fibre-Coax (HFC) Networks . . . . . . . . . . . . . . . . . . 511 11.1.5 Fibre-to-the-Curb/Street/Neighbourhood (FTTC/FTTS/FTTN) . . . 513 11.1.6 Passive Optical Networks (PONs) . . . . . . . . . . . . . . . . . . . 516 11.2 Mobile Telephone Base Station . . . . . . . . . . . . . . . . . . . . . . . 518 11.3 Further Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 519 Chapter 12. Research Directions . . . . . . . . . . . . . . . . . . . . . . . . 521 12.1 Solitons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 521 12.1.1 Dark Solitons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 522 12.1.2 Light Guiding Light (Spatial Solitons) . . . . . . . . . . . . . . . . . 522 12.2 Advanced Fibres . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 523 12.3 Plastic Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 523 12.3.1 Plastic Planar Waveguide Devices . . . . . . . . . . . . . . . . . . . 524 12.3.2 Plastic Semiconductor Lasers . . . . . . . . . . . . . . . . . . . . . 524 12.4 Optical Code Division Multiple Access (CDMA) . . . . . . . . . . . . . . 525 12.4.1 Direct Sequence Spread Spectrum (DSSS) . . . . . . . . . . . . . 527viii Understanding Optical Communications
  10. 10. 12.4.2 Code Division Multiple Access (CDMA) . . . . . . . . . . . . . . . . 528 12.4.3 Practical Optical CDMA . . . . . . . . . . . . . . . . . . . . . . . . . 53012.5 Optical Time Division Multiplexing (OTDM) . . . . . . . . . . . . . . . . 530 12.5.1 TDM Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 531 12.5.2 TDM Network Principles . . . . . . . . . . . . . . . . . . . . . . . . . 532 12.5.3 Optical TDM Principles . . . . . . . . . . . . . . . . . . . . . . . . . 533 12.5.4 Demultiplexing the TDM Signal . . . . . . . . . . . . . . . . . . . . . 53412.6 Optical Packet Switched Networks . . . . . . . . . . . . . . . . . . . . . 53512.7 Optical Interconnects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53712.8 Coherent Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53812.9 Further Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 541Appendix A. An Introduction to Semiconductors . . . . . . . . . . . . . . 543 A.1.1 Chemistry 101 Revisited . . . . . . . . . . . . . . . . . . . . . . . . . 543 A.1.2 Why Does a Conductor Conduct? . . . . . . . . . . . . . . . . . . . 546 A.1.3 Conductors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 548 A.1.4 Semiconductors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 549 A.1.5 p-n Junctions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 555 A.1.6 Semiconductor Junction Diodes . . . . . . . . . . . . . . . . . . . . . 555 A.1.7 The Bipolar Junction Transistor (BJT) . . . . . . . . . . . . . . . . . 557 A.1.8 Field Effect Transistors (FET) . . . . . . . . . . . . . . . . . . . . . . 560 A.1.9 Further Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 561Appendix B. An Introduction to Communications Networks . . . . . . . 563B.1 Function Layering and the ISO Model . . . . . . . . . . . . . . . . . . . . 563 B.1.1 Layered Communication Architectures . . . . . . . . . . . . . . . . . 563 B.1.2 The ISO Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 568B.2 Networks of Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 572 B.2.1 The Role of Optical Networks . . . . . . . . . . . . . . . . . . . . . . 574B.3 Further Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 575Appendix C. Laser Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . 577 C.1.1 Handling Fibre . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 579Appendix D. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 581Appendix E. Some Useful Facts . . . . . . . . . . . . . . . . . . . . . . . . 587 E.1.1 The Visible Spectrum . . . . . . . . . . . . . . . . . . . . . . . . . . . 587E.2 Units of Measure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 587 E.2.1 Fractions and Multiples . . . . . . . . . . . . . . . . . . . . . . . . . . 587E.3 Some Basic Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 588E.4 Wavelength Hall of Fame . . . . . . . . . . . . . . . . . . . . . . . . . . . 590Appendix F. Special Notices . . . . . . . . . . . . . . . . . . . . . . . . . . . 591How to Get ITSO Redbooks . . . . . . . . . . . . . . . . . . . . . . . . . . . . 593How IBM Employees Can Get ITSO Redbooks . . . . . . . . . . . . . . . . . 593How Customers Can Get ITSO Redbooks . . . . . . . . . . . . . . . . . . . . 594IBM Redbook Order Form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 595Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 597ITSO Redbook Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 599 Contents ix
  11. 11. x Understanding Optical Communications
  12. 12. Figures 1. Optical Transmission - Schematic . . . . . . . . . . . . . . . . . . . . . . . . 4 2. The Electromagnetic Spectrum . . . . . . . . . . . . . . . . . . . . . . . . 17 3. The Structure of an Electromagnetic Wave . . . . . . . . . . . . . . . . . 18 4. Amplitude Fluctuation in an Electromagnetic Wave . . . . . . . . . . . . . 19 5. Circular Polarisation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 6. Youngs Experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 7. Interference Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 8. Reflection of Light from a Glass/Air Interface . . . . . . . . . . . . . . . . 23 9. Interference Effects when passing Light through a Glass Sheet . . . . . 23 10. Variation in Reflectance with Thickness of Glass Sheet . . . . . . . . . . 24 11. Basic Principle of Light Transmission on Optical Fibre . . . . . . . . . . . 25 12. Effect of Dispersion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 13. Typical Fibre Infrared Absorption Spectrum . . . . . . . . . . . . . . . . . 31 14. Transmission Windows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 15. Fibre Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 16. Multimode Step-Index Fibre . . . . . . . . . . . . . . . . . . . . . . . . . . 34 17. Multimode Graded index Fibre . . . . . . . . . . . . . . . . . . . . . . . . . 35 18. Single-Mode Fibre . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 19. Fibre Refractive Index Profiles . . . . . . . . . . . . . . . . . . . . . . . . . 36 20. Light Propagation in Multimode Fibre . . . . . . . . . . . . . . . . . . . . . 39 21. Reflection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 22. Refraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 23. Refraction (2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 24. Critical Angle (1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 25. Critical Angle (2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 26. Calculating the Numerical Aperture . . . . . . . . . . . . . . . . . . . . . . 42 27. Multimode Propagation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 28. Spiral Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 29. Propagation around a Bend in the Fibre . . . . . . . . . . . . . . . . . . . 46 30. Effect of a Micro-Bend . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 31. Typical Speckle Pattern . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 32. Multimode Ray Propagation . . . . . . . . . . . . . . . . . . . . . . . . . . 49 33. Origin of Modal Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 34. Energy Distribution of Some TEM Modes . . . . . . . . . . . . . . . . . . 56 35. Energy Distribution of Some LP Modes in Fibre . . . . . . . . . . . . . . . 56 36. Single-Mode Propagation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 37. Mode Field Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 38. Fields at the End of the Fibre . . . . . . . . . . . . . . . . . . . . . . . . . 58 39. Reason for Bend Loss in Single-Mode Fibre . . . . . . . . . . . . . . . . . 58 40. Dispersion of “Standard” Single-Mode Fibre . . . . . . . . . . . . . . . . . 59 41. Dispersion Shifted Fibre . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 42. Profiles of Dispersion Shifted and Dispersion Flattened Fibre . . . . . . . 62 43. Non-Zero Dispersion-Shifted Fibre RI Profile . . . . . . . . . . . . . . . . 63 44. Polarisation Maintaining Fibre . . . . . . . . . . . . . . . . . . . . . . . . . 65 45. Axes of Polarisation in PMF . . . . . . . . . . . . . . . . . . . . . . . . . . 66 46. Pattern of Return Loss Variation by Wavelength . . . . . . . . . . . . . . 67 47. Four Wave Mixing Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 48. SBS Threshold Variation with Wavelength . . . . . . . . . . . . . . . . . . 71 49. Stimulated Raman Scattering . . . . . . . . . . . . . . . . . . . . . . . . . 72 50. Absorption Spectrum of Plastic Optical Fibre . . . . . . . . . . . . . . . . 75© Copyright IBM Corp. 1998 xi
  13. 13. 51. HPCF Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 52. Attenuation of HPCF in the Short Wavelength Band . . . . . . . . . . . . 77 53. Electrical Potentials across a p-n Junction . . . . . . . . . . . . . . . . . . 83 54. Bandgap Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 55. Simple P-N Junction LED . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 56. Double Heterojunction LED . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 57. Energy Bands in a Double Heterojunction . . . . . . . . . . . . . . . . . . 87 58. Exploded Structure of an Idealised Double Heterojunction LED . . . . . . 89 59. Schematic Structure of a Burrus LED . . . . . . . . . . . . . . . . . . . . . 89 60. Schematic Structure of an Edge Emitting LED . . . . . . . . . . . . . . . . 90 61. Coupling to a Fibre . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 62. Stimulated Emission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 63. Spontaneous Emission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 64. Energy States of a typical 4-Level Material . . . . . . . . . . . . . . . . . . 95 65. Lasing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 66. Fabry-Perot Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 67. Resonance Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 68. Resonance Modes in the Cavity of a Fabry-Perot Laser . . . . . . . . . 104 69. Modes Produced in a Typical Fabry-Perot Laser . . . . . . . . . . . . . 104 70. Spectral Width and Linewidth . . . . . . . . . . . . . . . . . . . . . . . . 105 71. Output Spectrum Changes as Power is Applied . . . . . . . . . . . . . . 106 72. Typical Mode Hopping Behaviour in an Unguided FP Laser . . . . . . . 107 73. Relaxation Oscillations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108 74. Directing the Light in a Fabry-Perot Laser . . . . . . . . . . . . . . . . . 110 75. Emission Profile of a Gain-Guided Fabry-Perot Laser . . . . . . . . . . 111 76. Fabry-Perot laser Output versus Input Current . . . . . . . . . . . . . . 112 77. DFB Laser - Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 78. DFB Laser with Phase Shifted Grating - Concept . . . . . . . . . . . . . 115 79. Phase Shifted Grating - Reflection Spectrum . . . . . . . . . . . . . . . 115 80. DFB Laser with Integrated Electro-Absorption Modulator . . . . . . . . . 116 81. DFB Laser with Electro-Absorption Modulator within the Cavity . . . . . 117 82. DBR Laser - Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118 83. Cavity Structure of a Multiple Quantum Well Laser . . . . . . . . . . . . 119 84. Tunable 2-Section DBR Laser . . . . . . . . . . . . . . . . . . . . . . . . 120 85. Tunable 3-Section DBR Laser . . . . . . . . . . . . . . . . . . . . . . . . 121 86. Sampled Grating - Schematic . . . . . . . . . . . . . . . . . . . . . . . . 122 87. Principle of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122 88. Sampled Grating Tunable DFB Laser - Schematic . . . . . . . . . . . . 123 89. External Cavity DBR Laser Schematic . . . . . . . . . . . . . . . . . . . 123 90. Stabilisation of Fabry-Perot Laser with a Fibre Bragg Grating . . . . . . 124 91. FP Laser with External FBG - Alternative Structure . . . . . . . . . . . . 125 92. VCSEL Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 93. In-Fibre Laser Using FBGs . . . . . . . . . . . . . . . . . . . . . . . . . . 127 94. Tuneable Fibre-Ring Laser . . . . . . . . . . . . . . . . . . . . . . . . . . 129 95. Upconversion Laser Operation . . . . . . . . . . . . . . . . . . . . . . . . 130 96. Some Energy Levels in Praseodymium Upconversion Lasers . . . . . . 131 97. Photoconductive Detector - Principle . . . . . . . . . . . . . . . . . . . . 133 98. Practical Photoconductive Detector - Schematic . . . . . . . . . . . . . . 134 99. Typical Silicon P-I-N Diode Schematic . . . . . . . . . . . . . . . . . . . 135 100. Schottky-Barrier Photodiode Schematic . . . . . . . . . . . . . . . . . . . 138 101. Avalanche Photodiode (APD) . . . . . . . . . . . . . . . . . . . . . . . . 139 102. Avalanche (Amplification) Process . . . . . . . . . . . . . . . . . . . . . . 140 103. Electric Field Strengths in an APD . . . . . . . . . . . . . . . . . . . . . 141 104. Variation of Quantum Efficiency with Device Response . . . . . . . . . 144xii Understanding Optical Communications
  14. 14. 105. Travelling Wave Photodector - Principle . . . . . . . . . . . . . . . . . . 144106. Resonant-Cavity Photodetector - Principle . . . . . . . . . . . . . . . . . 145107. Bipolar Junction Transistor (BJT) . . . . . . . . . . . . . . . . . . . . . . 146108. Planar Waveguide Concept . . . . . . . . . . . . . . . . . . . . . . . . . 150109. An 8-Port Splitter Made by Cascading Y-Couplers . . . . . . . . . . . . 151110. Planar Crossover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151111. Manufacture of Planar Waveguides by Deposition/Etching . . . . . . . . 152112. Coupling Fibres to Planar Devices . . . . . . . . . . . . . . . . . . . . . 155113. Erbium Doped Fibre Amplifier (EDFA) - Function . . . . . . . . . . . . . 158114. Erbium Doped Optical Fibre Amplifier . . . . . . . . . . . . . . . . . . . . 159115. Energy Level States of Erbium . . . . . . . . . . . . . . . . . . . . . . . . 160116. Gain Curve of a Typical EDFA . . . . . . . . . . . . . . . . . . . . . . . . 162117. Response of Cascaded EDFAs . . . . . . . . . . . . . . . . . . . . . . . 163118. EDFA Behavior in Gain Saturation . . . . . . . . . . . . . . . . . . . . . 165119. Energy Levels in Erbium/Ytterbium Co-Doped Amplifier . . . . . . . . . 166120. Additional Pumping Options . . . . . . . . . . . . . . . . . . . . . . . . . 168121. Cladding Pump Configuration . . . . . . . . . . . . . . . . . . . . . . . . 169122. Two-Stage EDFA Line Amplifier with Shared Pump . . . . . . . . . . . 170123. Polarisation Insensitive EDFA . . . . . . . . . . . . . . . . . . . . . . . . 171124. Remote Pumping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172125. Amplifier Breakdown Resilience . . . . . . . . . . . . . . . . . . . . . . . 173126. OTDR Path in Link with EDFAs . . . . . . . . . . . . . . . . . . . . . . . 173127. Rhodamine-B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178128. 16-Way Planar Splitter with Amplification . . . . . . . . . . . . . . . . . . 179129. Semiconductor Optical Amplifier Relationship to Laser . . . . . . . . . . 180130. Wavelength Changing Using SRS . . . . . . . . . . . . . . . . . . . . . . 182131. Wavelength Shifter Using FBGs . . . . . . . . . . . . . . . . . . . . . . . 183132. Multistage Wavelength Shifting . . . . . . . . . . . . . . . . . . . . . . . 183133. 1320 nm Raman Amplifier Using In-Fibre Bragg Gratings . . . . . . . . 183134. Generating Blue Light via Second Harmonic Generation . . . . . . . . . 184135. Principle of Resonant Couplers . . . . . . . . . . . . . . . . . . . . . . . 186136. Power Transfer in a Resonant Coupler . . . . . . . . . . . . . . . . . . . 188137. Reciprocity Principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189138. Some Coupler Configurations . . . . . . . . . . . . . . . . . . . . . . . . 189139. Resonant Coupler in Planar Waveguide Technology . . . . . . . . . . . 190140. Cascaded 3 dB Couplers . . . . . . . . . . . . . . . . . . . . . . . . . . . 191141. Wavelength Selective Coupling and Splitting . . . . . . . . . . . . . . . 191142. Y-Coupler (Splitter) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193143. Star Couplers - Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . 194144. Fused Fibre Star Coupler . . . . . . . . . . . . . . . . . . . . . . . . . . . 194145. Mixing Plate Coupler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194146. Planar (Free Space) Star Coupler . . . . . . . . . . . . . . . . . . . . . . 195147. Concatenation of Multiple 3 dB Couplers to Form an 8-Way Star . . . 195148. Polarising Beamsplitter Prisms . . . . . . . . . . . . . . . . . . . . . . . . 196149. Splitting of Unpolarised Light into Two Components . . . . . . . . . . . 197150. Effect of Optic Axis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198151. Isolator Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199152. Four-Port Circulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200153. Multiplexing Bidirectional Traffic onto a Single Fibre Strand . . . . . . . 201154. Circulator - Path from Port 1 to Port 2 . . . . . . . . . . . . . . . . . . . 202155. Circulator - Path from Port 2 to Port 3 . . . . . . . . . . . . . . . . . . . 203156. Fibre Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204157. Fibre Loop Polarisation Controller . . . . . . . . . . . . . . . . . . . . . . 204158. Polarisation Control by Squeezing the Fibre . . . . . . . . . . . . . . . . 205 Figures xiii
  15. 15. 159. GRIN Lens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205 160. Grating Principle of Operation . . . . . . . . . . . . . . . . . . . . . . . . 207 161. Grating Profiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207 162. Wavelength Division Multiplexing with a Littrow Grating . . . . . . . . . 208 163. WDM with a Concave Mirror and a Littrow Grating . . . . . . . . . . . . 208 164. Double-Pass Grating Compressor . . . . . . . . . . . . . . . . . . . . . . 209 165. Pulse Compression with Grating Compressor . . . . . . . . . . . . . . . 210 166. In-Fibre Bragg Grating - Schematic . . . . . . . . . . . . . . . . . . . . . 211 167. Principle of Operation of Fibre Bragg Grating . . . . . . . . . . . . . . . 211 168. In-Fibre Bragg Grating - Parameters . . . . . . . . . . . . . . . . . . . . 212 169. In-Fibre Bragg Grating - Typical Reflection Spectra . . . . . . . . . . . . 213 170. Chirped FBG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214 171. Reflectance of a Chirped FBG . . . . . . . . . . . . . . . . . . . . . . . . 215 172. Reflected Power of a Strongly Chirped Grating - Apodised . . . . . . . 215 173. Reflection Profiles of a Chirped FBG . . . . . . . . . . . . . . . . . . . . 215 174. Blazed FBG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216 175. In-Fibre Bragg Grating - Single Phase-Shift . . . . . . . . . . . . . . . . 217 176. In-Fibre Bragg Grating - Multiple Phase Shifts . . . . . . . . . . . . . . . 217 177. Wavelength Variation with Temperature in FBGs . . . . . . . . . . . . . 218 178. FBG Packaging for Passive Thermal Compensation . . . . . . . . . . . 218 179. Writing the FBG into a Fibre Core - Interference Pattern Technique . . 220 180. Writing the FBG into a Fibre Core - Phase Mask Technique . . . . . . 221 181. Practical FBG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221 182. Waveguide Grating Router Basic Function . . . . . . . . . . . . . . . . . 222 183. Waveguide Grating Router . . . . . . . . . . . . . . . . . . . . . . . . . . 223 184. Distribution of Optical Power in the Input FSC . . . . . . . . . . . . . . . 224 185. Operation of the Output FSC . . . . . . . . . . . . . . . . . . . . . . . . . 224 186. Waveguide Grating Router with Single-Ported Input . . . . . . . . . . . 225 187. Insertion Loss Characteristics of an Early 8-Port WGR . . . . . . . . . . 225 188. WGR with Half-Wave Plate for Polarisation Independence . . . . . . . 226 189. Transmission Characteristics of Ideal Filters . . . . . . . . . . . . . . . . 228 190. Transmission Characteristics of Two Practical Filters . . . . . . . . . . . 228 191. Fabry-Perot Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229 192. Fabry-Perot Filter Characteristics . . . . . . . . . . . . . . . . . . . . . . 231 193. Cascading Fabry-Perot Filters of Different FSR . . . . . . . . . . . . . . 232 194. Fabry-Perot Filter Using Dielectric Mirrors . . . . . . . . . . . . . . . . . 233 195. Tunable Fibre Fabry-Perot Filter . . . . . . . . . . . . . . . . . . . . . . . 233 196. Cascading Tunable Fabry-Perot Filters of Different FSR . . . . . . . . . 234 197. In-Fibre Bragg Grating Used as a Filter . . . . . . . . . . . . . . . . . . . 235 198. Fibre Ring Resonators . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235 199. Amplified Fibre Ring Resonator . . . . . . . . . . . . . . . . . . . . . . . 236 200. Dielectric Filter based WDM Multiplexor/Demultiplexor . . . . . . . . . . 237 201. Digital Optical Switch (DOS) - Schematic . . . . . . . . . . . . . . . . . 239 202. Crossconnect Switch Element - Function . . . . . . . . . . . . . . . . . . 240 203. Cross-Connect Using a Resonant Coupler . . . . . . . . . . . . . . . . . 240 204. Cross-Connect Using an MZI Configuration . . . . . . . . . . . . . . . . 241 205. Non-Linear Optical Loop Mirror (NOLM) . . . . . . . . . . . . . . . . . . 242 206. NOLM Output Power Variation with Input Power . . . . . . . . . . . . . 243 207. NOLM Filtering Out the Noise from a Stream of Pulses . . . . . . . . . 243 208. Non-Linear Amplifying Optical Loop Mirror (NALM) . . . . . . . . . . . . 244 209. Demultiplexing of a TDM Data Stream . . . . . . . . . . . . . . . . . . . 245 210. NOLM Configured as an AND Logic Gate . . . . . . . . . . . . . . . . . 245 211. NOLM Logic Gate Using TWSLA . . . . . . . . . . . . . . . . . . . . . . 246 212. Add-Drop Multiplexor - Functional View . . . . . . . . . . . . . . . . . . . 246xiv Understanding Optical Communications
  16. 16. 213. MZI Add-Drop Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247214. Acoustic Modulator - Bragg Reflection . . . . . . . . . . . . . . . . . . . 249215. Acoustic Modulator - Debye-Sears Effect . . . . . . . . . . . . . . . . . . 251216. Wavelength Selective Switching Function . . . . . . . . . . . . . . . . . 252217. Acoustooptic Tunable Filter (AOTF) - Basic Structure . . . . . . . . . . 253218. AOTF Operation (1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254219. AOTF Operation (2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254220. Electro-Optic Phase Modulator . . . . . . . . . . . . . . . . . . . . . . . . 256221. Mach-Zehnder Interferometer . . . . . . . . . . . . . . . . . . . . . . . . 256222. Modulator Using Mach-Zehnder Interferometer . . . . . . . . . . . . . . 257223. Travelling-Wave Principle . . . . . . . . . . . . . . . . . . . . . . . . . . . 258224. Pockels Cell Modulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259225. Faraday Effect Modulator . . . . . . . . . . . . . . . . . . . . . . . . . . . 260226. Principle of Drawing a Fibre . . . . . . . . . . . . . . . . . . . . . . . . . 269227. Drawing Tower . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269228. Double-Crucible Method . . . . . . . . . . . . . . . . . . . . . . . . . . . 270229. Outside Vapour Deposition . . . . . . . . . . . . . . . . . . . . . . . . . . 271230. Vapour Axial Deposition (VAD) . . . . . . . . . . . . . . . . . . . . . . . 273231. Modified Chemical Vapour Deposition . . . . . . . . . . . . . . . . . . . 274232. Fusion Splicing Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . 276233. Fibre Alignment Using Optical Feedback . . . . . . . . . . . . . . . . . . 277234. Sources of Loss due to Misalignment in Fibre Joins . . . . . . . . . . . 280235. Sources of Intrinsic Loss in Fibre Joins . . . . . . . . . . . . . . . . . . . 281236. Some Typical Connector Types . . . . . . . . . . . . . . . . . . . . . . . 283237. MT Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284238. ESCON Fibre Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . 285239. Primary Coated Optical Fibre (PCOF) . . . . . . . . . . . . . . . . . . . 287240. Secondary Coated Optical Fibre (SCOF) . . . . . . . . . . . . . . . . . . 288241. Loose Tube Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . 288242. Single-Core Cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289243. Dual Indoor Cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290244. 6-Core Tight Buffered Indoor Cable . . . . . . . . . . . . . . . . . . . . . 290245. Typical Outdoor Fiber Cable (Loose Tube - Gel Filled) . . . . . . . . . . 292246. Segmented-Core Cable Design . . . . . . . . . . . . . . . . . . . . . . . 292247. Outdoor Aerial Cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292248. 12-Core Optical Flat Cable . . . . . . . . . . . . . . . . . . . . . . . . . . 293249. Typical Undersea Cable Design . . . . . . . . . . . . . . . . . . . . . . . 293250. Conventional Long Distance Fibre Transmission System . . . . . . . . 297251. Repeater Function Compared with Amplification . . . . . . . . . . . . . 298252. Amplified Single-Channel Transmission System . . . . . . . . . . . . . . 299253. WDM Long Distance Fibre Transmission System . . . . . . . . . . . . . 301254. NRZ Coding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302255. Evolution of an Optical Pulse . . . . . . . . . . . . . . . . . . . . . . . . . 302256. NRZI Encoding Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 304257. Return-To-Zero (RZ) Coding . . . . . . . . . . . . . . . . . . . . . . . . . 305258. Four-Level Coding Example . . . . . . . . . . . . . . . . . . . . . . . . . 307259. Duo-Binary Code Example . . . . . . . . . . . . . . . . . . . . . . . . . . 307260. Digital Receiver Functions . . . . . . . . . . . . . . . . . . . . . . . . . . 309261. Operating Principle of a Continuous (Analogue) PLL . . . . . . . . . . . 311262. Receiving 4 out of 5 Code . . . . . . . . . . . . . . . . . . . . . . . . . . 315263. Power Budgeting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 318264. Dispersion Compensation of an Existing Standard Fibre Link . . . . . . 330265. Dispersion Compensation Using a Mid-Span DCF . . . . . . . . . . . . 331266. Dispersion Compensation of a New Link with DCF . . . . . . . . . . . . 332 Figures xv
  17. 17. 267. Spectral Inverter - Schematic . . . . . . . . . . . . . . . . . . . . . . . . 333 268. Spectral Inversion - Wavelength (Frequency) Domain . . . . . . . . . . 333 269. Dispersion Compensation with a Fibre Bragg Grating . . . . . . . . . . 334 270. Radial Overfilled Launch (ROFL) . . . . . . . . . . . . . . . . . . . . . . 339 271. Pulse Breakup and the Fibre RI Profile that Causes It . . . . . . . . . . 339 272. Optical Power Meter - Logical Structure . . . . . . . . . . . . . . . . . . 342 273. OTDR Display - Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . 343 274. OTDR Operational Logic . . . . . . . . . . . . . . . . . . . . . . . . . . . 345 275. Spectrum Analyser - Display Schematic . . . . . . . . . . . . . . . . . . 346 276. Spectrum Analyser - Logical Structure . . . . . . . . . . . . . . . . . . . 347 277. Eye Diagram - Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . 348 278. Real Eye Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349 279. FDDI Basic Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354 280. FDDI Ring Healing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355 281. FDDI Ring Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . 355 282. Ten-Bit Elasticity Buffer Operation . . . . . . . . . . . . . . . . . . . . . . 359 283. Optical Bypass Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362 284. Physical Layer Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . 362 285. FDDI Node Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 364 286. Ethernet Bus Topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366 287. Ethernet Hub Topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . 368 288. Relationship between Offered Load and Throughput on Ethernet . . . . 370 289. Fibre Channel Point-to-Point Topology . . . . . . . . . . . . . . . . . . . 375 290. Fibre Channel Crosspoint Switch Topology . . . . . . . . . . . . . . . . 376 291. Fibre Channel Arbitrated Loop Topologies . . . . . . . . . . . . . . . . . 376 292. Fibre Channel Physical Nomenclature . . . . . . . . . . . . . . . . . . . 377 293. Open Fibre Control System - Logic Structure . . . . . . . . . . . . . . . 380 294. Principle of the ESCON Director (Circuit Switch) . . . . . . . . . . . . . 382 295. OptiConnect System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 386 296. The Multiplexor Mountain . . . . . . . . . . . . . . . . . . . . . . . . . . . 388 297. Sonet STS-1 Frame Structure . . . . . . . . . . . . . . . . . . . . . . . . 390 298. Sonet Synchronous Payload Envelope (SPE) . . . . . . . . . . . . . . . 390 299. Synchronous Payload Envelope Floating in STS-1 Frame . . . . . . . . 391 300. STM-1 to STM-4 Synchronous Multiplexing . . . . . . . . . . . . . . . . 391 301. SDH Basic Frame Format . . . . . . . . . . . . . . . . . . . . . . . . . . 392 302. Sonet Ring Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393 303. Sonet Ring Restored after Cable Break . . . . . . . . . . . . . . . . . . 394 304. ATM Network Structure Overview . . . . . . . . . . . . . . . . . . . . . . 399 305. Routing Concept in an ATM Network . . . . . . . . . . . . . . . . . . . . 402 306. Simple (Sparse) WDM . . . . . . . . . . . . . . . . . . . . . . . . . . . . 411 307. WDM Functions Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . 412 308. Spectrum of Dense WDM and Sparse WDM on the Same Fibre . . . . 413 309. Multiwavelength Laser . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 416 310. Idealised Output Spectrum of a Multiline Laser . . . . . . . . . . . . . . 417 311. FP Laser Output Spectrum Just Below Threshold . . . . . . . . . . . . . 418 312. Multiline Laser Design Based on ASE . . . . . . . . . . . . . . . . . . . 418 313. Splitter Array with Fabry-Perot Filters . . . . . . . . . . . . . . . . . . . . 421 314. Demultiplexor Using In-Fibre Bragg Gratings . . . . . . . . . . . . . . . 421 315. Demultiplexor Using In-Fibre Bragg Gratings with 3 dB Couplers . . . 422 316. Array Waveguide Wavelength Router Schematic . . . . . . . . . . . . . 423 317. Bi-Directional Wavelength Multiplexor/Demultiplexor . . . . . . . . . . . 423 318. Wavelength Multiplexor/Demultiplexor . . . . . . . . . . . . . . . . . . . 424 319. Add-Drop Multiplexor Function . . . . . . . . . . . . . . . . . . . . . . . . 424 320. Array Waveguide Add-Drop Multiplexor . . . . . . . . . . . . . . . . . . . 425xvi Understanding Optical Communications
  18. 18. 321. Add-Drop Multiplexor Using FBG and Circulators . . . . . . . . . . . . . 425322. Filter Using Cascaded Mach-Zehnder Interferometers . . . . . . . . . . 426323. ADM Using Cascaded Mach-Zehnder Interferometers - Principle . . . . 426324. Add-Drop Multiplexor Using Cascaded Mach-Zehnder Interferometers . 427325. 4 x 4 Optical Space-Division Switch . . . . . . . . . . . . . . . . . . . . . 428326. Optical Switch Using Crossconnect Switch Elements . . . . . . . . . . . 429327. Structure of an Optical Switching Node . . . . . . . . . . . . . . . . . . . 430328. Optical Switching Node with Wavelength Conversion . . . . . . . . . . . 431329. Wavelength Converter with Cross-Gain Modulated SOA . . . . . . . . . 433330. Wavelength Converter with Cross-Phase Modulated SOA . . . . . . . . 434331. Wavelength Converter Using FWM or DFG . . . . . . . . . . . . . . . . 435332. Fitting Optical Channels into Their Allocated Wavebands . . . . . . . . 438333. A More Practical Waveband Allocation . . . . . . . . . . . . . . . . . . . 439334. Effect of Non-Square Filter on Signal Pulse . . . . . . . . . . . . . . . . 439335. Effect of Multiple Filters on Signal Pulse . . . . . . . . . . . . . . . . . . 440336. Broadcast and Select Network - Principle . . . . . . . . . . . . . . . . . 462337. Add-Drop Multiplexing Concept . . . . . . . . . . . . . . . . . . . . . . . 462338. Add-Drop Multiplexed Ring Network . . . . . . . . . . . . . . . . . . . . 463339. Network Using Optical Switching Nodes . . . . . . . . . . . . . . . . . . 465340. Wavelength Selective Network - Concept . . . . . . . . . . . . . . . . . 466341. Ring Wiring Concentrator . . . . . . . . . . . . . . . . . . . . . . . . . . . 468342. Folded Bus Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . 469343. Reflective Star Configuration . . . . . . . . . . . . . . . . . . . . . . . . . 470344. Tree Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 471345. Wavelength Switching System . . . . . . . . . . . . . . . . . . . . . . . . 476346. Rainbow-1 System Design . . . . . . . . . . . . . . . . . . . . . . . . . . 480347. Add/Drop WDM Network with Multiwavelength Source . . . . . . . . . . 482348. Add/Drop WDM Station with Multiwavelength Source . . . . . . . . . . 483349. The IBM 9729 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 486350. The IBM 9729 System Configuration . . . . . . . . . . . . . . . . . . . . 487351. IBM 9729 System Structure . . . . . . . . . . . . . . . . . . . . . . . . . 488352. IBM 9729 Wavelength Allocation . . . . . . . . . . . . . . . . . . . . . . 490353. IBM 9729 Major Components and Data Flow . . . . . . . . . . . . . . . 491354. Grating Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 492355. Grating Assembly Schematic . . . . . . . . . . . . . . . . . . . . . . . . . 492356. End-to-End Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . 495357. Evolution of an Optical Pulse . . . . . . . . . . . . . . . . . . . . . . . . . 497358. IBM 9729 Network Management Configuration . . . . . . . . . . . . . . 500359. IBM 9729 Ring Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . 501360. First Generation WAN WDM System - Architecture . . . . . . . . . . . . 502361. Network Management Channel . . . . . . . . . . . . . . . . . . . . . . . 504362. Traditional Telephone Local-Loop Cabling . . . . . . . . . . . . . . . . . 509363. Traditional Cable TV System Cabling . . . . . . . . . . . . . . . . . . . . 510364. Hybrid Fibre-Coax (HFC) Network Cabling . . . . . . . . . . . . . . . . . 511365. Proposed Spectrum Allocation for Bi-Directional HFC . . . . . . . . . . 512366. Fibre-to-the-Curb Cabling Alternatives . . . . . . . . . . . . . . . . . . . 513367. Cambridge Trial Network - Structure . . . . . . . . . . . . . . . . . . . . 515368. Passive Optical Network - Potential Solutions . . . . . . . . . . . . . . . 516369. Mobile Cellular Telephone System with Remote Central Base Station . 518370. Communication System - Logical View . . . . . . . . . . . . . . . . . . . 518371. Direct Sequence Spread Spectrum Modulation - Transmitter . . . . . . 527372. Direct Sequence Spread Spectrum Modulation . . . . . . . . . . . . . . 528373. Time Division Multiplexing (TDM) - Concept . . . . . . . . . . . . . . . . 531374. Principle of a TDM Network . . . . . . . . . . . . . . . . . . . . . . . . . 532 Figures xvii
  19. 19. 375. Optical TDM Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . 533 376. Demultiplexing the OTDM Stream . . . . . . . . . . . . . . . . . . . . . . 535 377. Packet Switching - Principle . . . . . . . . . . . . . . . . . . . . . . . . . 535 378. An Optical Transmission System Using Coherent Detection . . . . . . . 539 379. Bohr Model of the Atom . . . . . . . . . . . . . . . . . . . . . . . . . . . . 543 380. Electron Orbits (Shells) in the Silicon Atom . . . . . . . . . . . . . . . . 544 381. Oxygen Atom Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . 545 382. Energy Bands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 546 383. Energy Bands and Electrical Conduction . . . . . . . . . . . . . . . . . . 547 384. Electricity Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 548 385. Silicon Crystal Lattice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 550 386. Conduction in an Intrinsic Semiconductor . . . . . . . . . . . . . . . . . 550 387. Doped Silicon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 550 388. Doped Silicon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 552 389. Free Electron Movement within a Crystal Lattice . . . . . . . . . . . . . 554 390. p-n Junction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 555 391. Electrical Potentials across a p-n Junction . . . . . . . . . . . . . . . . . 556 392. Basic BJT Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . 557 393. Practical Construction of a BJT . . . . . . . . . . . . . . . . . . . . . . . 558 394. Bipolar Junction Transistor (BJT) in VLSI Implementation . . . . . . . . 558 395. Operation of a BJT Stage 1 . . . . . . . . . . . . . . . . . . . . . . . . . 559 396. Operation of a BJT Stage 2 . . . . . . . . . . . . . . . . . . . . . . . . . 559 397. Insulated Gate Field Effect Transistor (IGFET) . . . . . . . . . . . . . . 560 398. Communications Protocol - Principle . . . . . . . . . . . . . . . . . . . . 565 399. Communications Protocol - Principle . . . . . . . . . . . . . . . . . . . . 566 400. Communications Protocol - Network Problem . . . . . . . . . . . . . . . 567 401. Layering of Functions in the ISO Model . . . . . . . . . . . . . . . . . . 568 402. OSI Data Frame Format . . . . . . . . . . . . . . . . . . . . . . . . . . . 569 403. Scope of Layers - 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 570 404. Sub-Layers and Networks . . . . . . . . . . . . . . . . . . . . . . . . . . 571 405. ATM, POTS and X.25 over an SDH/Sonet Backbone . . . . . . . . . . 572 406. Network Replaces a Point-to-Point Physical Link . . . . . . . . . . . . . 573 407. A Network Replaces a Link within Another Network. . . . . . . . . . . . 574 408. Hazard Warning Symbol Designating Laser in Operation . . . . . . . . 577 409. The Visible Spectrum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 587xviii Understanding Optical Communications
  20. 20. Tables 1. Bandgap Energy and Possible Wavelength Ranges in Various Materials 85 2. Connector Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . 284 3. Optical Fibre State of the Art . . . . . . . . . . . . . . . . . . . . . . . . . 316 4. Signal Loss in Various Materials . . . . . . . . . . . . . . . . . . . . . . . 316 5. FDDI Code Translation Table . . . . . . . . . . . . . . . . . . . . . . . . 360 6. Fibre Channel Media Capabilities . . . . . . . . . . . . . . . . . . . . . . 377 7. Sonet Speed Hierarchy . . . . . . . . . . . . . . . . . . . . . . . . . . . . 392 8. PDH Speed Hierarchy - USA . . . . . . . . . . . . . . . . . . . . . . . . . 394 9. PDH Speed Hierarchy - Europe . . . . . . . . . . . . . . . . . . . . . . . 394 10. ATM-UNI Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 405© Copyright IBM Corp. 1998 xix
  21. 21. xx Understanding Optical Communications
  22. 22. Preface This book presents a high level technical overview of the emerging technologies of fibre optical communications and optical networking. Written at the “technical conceptual” level it is intended as an introduction to the field for computer and data communication professionals. Discussion is descriptive and an effort has been made to keep the use of mathematics to a minimum. Although it is intended for professionals who already have some technical background, it is nevertheless relevant to anyone wishing to understand optical communication. The primary topics of the book are: Transmission of light on a fibre Optical fibre, lasers, detectors, optical components Use of fibre optics in electronic communications networks Wavelength Division Multiplexing (WDM) Optical communications networksAbout the Author Harry J. R. Dutton is a Project Leader with the IBM International Technical Support Center, Raleigh NC., USA. Possibly the worlds longest-distance “remote report” he is based in Sydney, Australia. His current responsibilities are for worldwide technical support of ATM and of optical communications architectures and standards. On joining IBM in January of 1967 as a Systems Engineer, Harry initially specialised in the design and programming of early communication networks. Since then he has worked in communications system design, software design, communications systems programming, product design, customer technical support, project management, consulting and product management. Throughout, his predominant role has been as the interface (on technical matters) between the IBM field companies and product development laboratories. A frequent speaker at international conferences, he is the author of 18 IBM publications in the areas of X.25, SNA Architecture, Voice/Data Integration, Micro Channel, High Speed Communications and ATM. Harry is a graduate of the University of New South Wales and a member of the IEEE. He may be contacted by email on: dutton@au1.ibm.comBy the Same Author Asynchronous Transfer Mode (ATM) - Technical Overview by Harry J. R. Dutton and Peter Lenhard. Prentice Hall, 1995. High-Speed Networking Technology: An Introductory Survey by Harry J. R. Dutton and Peter Lenhard. Prentice Hall, 1995.© Copyright IBM Corp. 1998 xxi
  23. 23. Acknowledgments This book was written as a project of the IBM International Technical Support Centre, Raleigh. Producing a book like this is not a task that any mortal can perform in isolation. Thanks are due to the following people for help, advice, technical guidance and review: Dr Leon Polladian The University of Sydney, Sydney, Australia. Mr Denis Kekas The University of Arizona, Tucson, AZ. Mr Jon A. Herlocker The University of Arizona, Tucson, AZ. Mr James Cleaver IBM Australia Limited, Sydney, Australia. Dr Cassimer DeCussatis IBM Enterprise Systems Division, Poughkeepsie, NY. Dr Frank Janniello IBM Research Division, Hawthorne, NY. Dr Daniel Kuchta IBM Research Division, Yorktown, NY. Mr John Kuras IBM Network Hardware Division, Raleigh, NC. Mr Ian Shields IBM Network Software Division, Raleigh, NC. Mr Gary Steps IBM Network Hardware Division, Raleigh, NC. Mr Shawn Walsh IBM International Technical Support Organisation, Raleigh, NC. Mr Walter A. Worischek IBM Austria, Vienna, Austria.Comments Welcome Your comments are important to us! We want our redbooks to be as helpful as possible. Please send us your comments about this or other redbooks in one of the following ways: Fax the evaluation form found in “ITSO Redbook Evaluation” on page 599 to the fax number shown on the form. Use the electronic evaluation form found on the Redbooks Web sites: For Internet users http://www.redbooks.ibm.com/ For IBM Intranet users http://w3.itso.ibm.com/ Send us a note at the following address: redbook@us.ibm.comxxii Understanding Optical Communications
  24. 24. Part 1. Theory and Devices© Copyright IBM Corp. 1998 1
  25. 25. 2 Understanding Optical Communications

×