Understanding Optical Communications.pdf

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SG245230
ÉÂÔ
Understanding Optical Communications
Harry J. R. Dutton
International Technical Support Organization
http://www.redbooks.ibm.com
SG24-5230-00
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ÉÂÔ
International Technical Support Organization
SG24-5230-00
Understanding Optical Communications
September 1998
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 Organization
Dept. HZ8 Building 678
P.O. Box 12195
Research Triangle Park, NC 27709-2195
When you send information to IBM, you grant IBM a non-exclusive right to use or distribute the information in any way it believes
appropriate without incurring any obligation to you.
Ò 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 to
restrictions set forth in GSA ADP Schedule Contract with IBM Corp.
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Contents
Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi
Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xix
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxi
About the Author .................................... xxi
By the Same Author .................................. xxi
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxii
Comments Welcome . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxii
Part 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 Snell's 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
Ò Copyright IBM Corp. 1998
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