Fiber-Optic Communications Systems, Third Edition. Govind ... Help...

Click here to load reader

  • date post

    16-Jan-2020
  • Category

    Documents

  • view

    57
  • download

    6

Embed Size (px)

Transcript of Fiber-Optic Communications Systems, Third Edition. Govind ... Help...

  • Fiber-Optic Communications Systems, Third Edition. Govind P. Agrawal Copyright  2002 John Wiley & Sons, Inc.

    ISBNs: 0-471-21571-6 (Hardback); 0-471-22114-7 (Electronic)

  • Fiber-Optic Communication Systems Third Edition

    GOVIND E? AGRAWAL

    The Institute of Optics University of Rochester Rochester: NY

    WILEY- 623 INTERSCIENCE A JOHN WILEY & SONS, INC., PUBLICATION

  • Designations used by companies to distinguish their products are often claimed as trademarks. In all instances where John Wiley & Sons, Inc., is aware of a claim, the product names appear in initial capital or ALL CAPITAL LETTERS. Readers, however, should contact the appropriate companies for more complete information regarding trademarks and registration.

    Copyright  2002 by John Wiley & Sons, Inc. All rights reserved.

    No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic or mechanical, including uploading, downloading, printing, decompiling, recording or otherwise, except as permitted under Sections 107 or 108 of the 1976 United States Copyright Act, without the prior written permission of the Publisher. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 605 Third Avenue, New York, NY 10158-0012, (212) 850-6011, fax (212) 850-6008, E-Mail: [email protected]

    This publication is designed to provide accurate and authoritative information in regard to the subject matter covered. It is sold with the understanding that the publisher is not engaged in rendering professional services. If professional advice or other expert assistance is required, the services of a competent professional person should be sought.

    ISBN 0-471-22114-7

    This title is also available in print as ISBN 0-471-21571-6.

    For more information about Wiley products, visit our web site at www.Wiley.com.

  • For My Parents

  • Contents

    Preface xv

    1 Introduction 1 1.1 Historical Perspective . . . . . . . . . . . . . . . . . . . . . . . . . . 1

    1.1.1 Need for Fiber-Optic Communications . . . . . . . . . . . . 2 1.1.2 Evolution of Lightwave Systems . . . . . . . . . . . . . . . . 4

    1.2 Basic Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 1.2.1 Analog and Digital Signals . . . . . . . . . . . . . . . . . . . 8 1.2.2 Channel Multiplexing . . . . . . . . . . . . . . . . . . . . . 11 1.2.3 Modulation Formats . . . . . . . . . . . . . . . . . . . . . . 13

    1.3 Optical Communication Systems . . . . . . . . . . . . . . . . . . . . 15 1.4 Lightwave System Components . . . . . . . . . . . . . . . . . . . . 16

    1.4.1 Optical Fibers as a Communication Channel . . . . . . . . . . 17 1.4.2 Optical Transmitters . . . . . . . . . . . . . . . . . . . . . . 17 1.4.3 Optical Receivers . . . . . . . . . . . . . . . . . . . . . . . . 18

    Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

    2 Optical Fibers 23 2.1 Geometrical-Optics Description . . . . . . . . . . . . . . . . . . . . 23

    2.1.1 Step-Index Fibers . . . . . . . . . . . . . . . . . . . . . . . . 24 2.1.2 Graded-Index Fibers . . . . . . . . . . . . . . . . . . . . . . 26

    2.2 Wave Propagation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 2.2.1 Maxwell’s Equations . . . . . . . . . . . . . . . . . . . . . . 29 2.2.2 Fiber Modes . . . . . . . . . . . . . . . . . . . . . . . . . . 31 2.2.3 Single-Mode Fibers . . . . . . . . . . . . . . . . . . . . . . . 34

    2.3 Dispersion in Single-Mode Fibers . . . . . . . . . . . . . . . . . . . 37 2.3.1 Group-Velocity Dispersion . . . . . . . . . . . . . . . . . . . 38 2.3.2 Material Dispersion . . . . . . . . . . . . . . . . . . . . . . . 39 2.3.3 Waveguide Dispersion . . . . . . . . . . . . . . . . . . . . . 41 2.3.4 Higher-Order Dispersion . . . . . . . . . . . . . . . . . . . . 42 2.3.5 Polarization-Mode Dispersion . . . . . . . . . . . . . . . . . 43

    2.4 Dispersion-Induced Limitations . . . . . . . . . . . . . . . . . . . . 45 2.4.1 Basic Propagation Equation . . . . . . . . . . . . . . . . . . 46

    vii

  • viii CONTENTS

    2.4.2 Chirped Gaussian Pulses . . . . . . . . . . . . . . . . . . . . 47 2.4.3 Limitations on the Bit Rate . . . . . . . . . . . . . . . . . . . 50 2.4.4 Fiber Bandwidth . . . . . . . . . . . . . . . . . . . . . . . . 53

    2.5 Fiber Losses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 2.5.1 Attenuation Coefficient . . . . . . . . . . . . . . . . . . . . . 55 2.5.2 Material Absorption . . . . . . . . . . . . . . . . . . . . . . 56 2.5.3 Rayleigh Scattering . . . . . . . . . . . . . . . . . . . . . . . 57 2.5.4 Waveguide Imperfections . . . . . . . . . . . . . . . . . . . . 58

    2.6 Nonlinear Optical Effects . . . . . . . . . . . . . . . . . . . . . . . . 59 2.6.1 Stimulated Light Scattering . . . . . . . . . . . . . . . . . . 59 2.6.2 Nonlinear Phase Modulation . . . . . . . . . . . . . . . . . . 64 2.6.3 Four-Wave Mixing . . . . . . . . . . . . . . . . . . . . . . . 66

    2.7 Fiber Manufacturing . . . . . . . . . . . . . . . . . . . . . . . . . . 67 2.7.1 Design Issues . . . . . . . . . . . . . . . . . . . . . . . . . . 67 2.7.2 Fabrication Methods . . . . . . . . . . . . . . . . . . . . . . 68 2.7.3 Cables and Connectors . . . . . . . . . . . . . . . . . . . . . 70

    Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

    3 Optical Transmitters 77 3.1 Basic Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

    3.1.1 Emission and Absorption Rates . . . . . . . . . . . . . . . . 78 3.1.2 p–n Junctions . . . . . . . . . . . . . . . . . . . . . . . . . . 81 3.1.3 Nonradiative Recombination . . . . . . . . . . . . . . . . . . 83 3.1.4 Semiconductor Materials . . . . . . . . . . . . . . . . . . . . 84

    3.2 Light-Emitting Diodes . . . . . . . . . . . . . . . . . . . . . . . . . 87 3.2.1 Power–Current Characteristics . . . . . . . . . . . . . . . . . 87 3.2.2 LED Spectrum . . . . . . . . . . . . . . . . . . . . . . . . . 89 3.2.3 Modulation Response . . . . . . . . . . . . . . . . . . . . . 90 3.2.4 LED Structures . . . . . . . . . . . . . . . . . . . . . . . . . 91

    3.3 Semiconductor Lasers . . . . . . . . . . . . . . . . . . . . . . . . . . 92 3.3.1 Optical Gain . . . . . . . . . . . . . . . . . . . . . . . . . . 93 3.3.2 Feedback and Laser Threshold . . . . . . . . . . . . . . . . . 94 3.3.3 Laser Structures . . . . . . . . . . . . . . . . . . . . . . . . 96

    3.4 Control of Longitudinal Modes . . . . . . . . . . . . . . . . . . . . . 99 3.4.1 Distributed Feedback Lasers . . . . . . . . . . . . . . . . . . 100 3.4.2 Coupled-Cavity Semiconductor Lasers . . . . . . . . . . . . 102 3.4.3 Tunable Semiconductor Lasers . . . . . . . . . . . . . . . . . 103 3.4.4 Vertical-Cavity Surface-Emitting Lasers . . . . . . . . . . . . 105

    3.5 Laser Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . 106 3.5.1 CW Characteristics . . . . . . . . . . . . . . . . . . . . . . . 107 3.5.2 Small-Signal Modulation . . . . . . . . . . . . . . . . . . . . 110 3.5.3 Large-Signal Modulation . . . . . . . . . . . . . . . . . . . . 112 3.5.4 Relative Intensity Noise . . . . . . . . . . . . . . . . . . . . 114 3.5.5 Spectral Linewidth . . . . . . . . . . . . . . . . . . . . . . . 116

    3.6 Transmitter Design . . . . . . . . . . . . . . . . . . . . . . . . . . . 118

  • CONTENTS ix

    3.6.1 Source–Fiber Coupling . . . . . . . . . . . . . . . . . . . . . 118 3.6.2 Driving Circuitry . . . . . . . . . . . . . . . . . . . . . . . . 121 3.6.3 Optical Modulators . . . . . . . . . . . . . . . . . . . . . . . 122 3.6.4 Optoelectronic Integration . . . . . . . . . . . . . . . . . . . 123 3.6.5 Reliability and Packaging . . . . . . . . . . . . . . . . . . . 124

    Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127

    4 Optical Receivers 133 4.1 Basic Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133

    4.1.1 Detector Responsivity . . . . . . . . . . . . . . . . . . . . . 133 4.1.2 Rise Time and Bandwidth . . . . . . . . . . . . . . . . . . . 135

    4.2 Common Photodetectors . . . . . . . . . . . . . . . . . . . . . . . . 136 4.2.1 p–n Photodiodes . . . . . . . . . . . . . . . . . . . . . . . . 137 4.2.2 p–i–n Photodiodes . . . . . . . . . . . . . . . . . . . . . . . 138 4.2.3 Avalanche Photodiodes . . . . . . . . . . . . . . . . . . . . . 142 4.2.4 MSM Photodetectors . . . . . . . . . . . . . . . . . . . . . . 148

    4.3 Receiver Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 4.3.1 Front End . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 4.3.2 Linear Channel . . . . . . . . . . . . . . . . . . . . . . . . . 150 4.3.3 Decision Circuit . . . . . . . . . . . . . . . . . . . . . . . . 152 4.3.4 Integrated Receivers . . . . . . . . . . . . . . . . . . . . . . 153

    4.4 Receiver Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 4.4.1 Noise Mechanisms . . . . . . . . . . . . . . . . . . . . . . . 156 4.4.2 p–i–n Receivers . . . . . . . . . . . . . . . . . . . . . . . . . 158 4.4.3 APD Receivers . . . . . . . . . . . . . . . . . . . . . . . . . 159

    4.5 Receiver Sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . 162 4