Erbium-Doped Fiber Amplifiers (Optics and Photonics) PDF
Preview Erbium-Doped Fiber Amplifiers (Optics and Photonics)
Erbium-Doped Fiber Amplifiers Fundamentals and Technology OPTICS AND PHOTONICS (formerly Quantum Electronics) EDITED BY PAUL L. KELLY TUBSU niversity Medford, Massachusetts IVAN KAMINOW AT&T Bell Laboratories Holmdel, New Jersey GOVMD AGRAWAL University of Rochester Rochester, New York A complete list of titles in this series appears at the end of this volume. Erbium-Doped Fiber Amplifiers Fundamentals and Technology .'F C. BECKER Passive Optical Networks Group Switching and Access Group Lucent Technologies Tokyo, Japan N. A. OLSSON Passive Optical Networks Group Switching and Access Group Lucent Technologies Murray Hill, New Jersey J. R. SIMPSON Ciena Corporation Linthicum, Maryland ACADEMIC PRESS San Diego London Boston NewYork Sydney Tokyo Toronto This book is printed on acid-free paper. @ Copyright 0 1999 by Lucent Technologies All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information storage and retrieval system, without permission in writing from the publisher. All brand names and product names mentioned in this book are trademarks or registered trademarks of their respective companies. Academic Press A Harcourt Science and Technology Company 525 B Street, Suite 1900, San Diego, CA 92101-4495, USA http://www.academicpress.com Academic Press Harcourt Place, 32 Jamestown Rd., London NW1 7BY, UK http://www.academicpress.com Library of Congress Cataloging-in-Publication Data Becker, P. C. Erbium-Doped Fiber Amplifiers: Fundamentals and Technology / P. C. Becker, N. A. Olsson, J. R. Simpson. p. cm. - (Optics and Photonics) Includes bibliographical references and index. ISBN 0-12-084590-3-ISBN 0-12-084591-1 (Diskette) 1. Optical communications - Equipment and supplies 2. Optical amplifiers. 3. Optical fibers I. Olsson, N. A. II. Simpson, J. R. In. Title IV. Series. TK5103.59.B43 1997 621.382’75 - DC21 97-29070 CIP Printed in the United States of America 00 01 0203 IP 9 8 7 6 5 4 3 2 Contents Foreword X Preface xiii Acknowledgements xv 1 INTRODUCTION 1 1.1 Long Haul Fiber Networks . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Historical Development of Erbium-Doped Fiber Amplifiers . . . . . 5 1.3 From Glass to Systems Outline . . . . . . . . . . . . . . . . . . . 9 2 OPTICAL FIBER FABRICATION 13 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2.2 Conventional Communication Fiber . . . . . . . . . . . . . . . . . . 14 2.3 Rare Earth Doped Fibers . . . . . . . . . . . . . . . . . . . . . . . . 16 2.3.1 Rare Earth Vapor Phase Delivery Methods . . . . . . . . . . 16 2.3.2 Rare Earth Solution-DopingM ethods . . . . . . . . . . . . . 21 2.3.3 Rod and Tube Methods . . . . . . . . . . . . . . . . . . . . 23 2.4 Pump-Signal Interaction Methods . . . . . . . . . . . . . . . . . . . 25 2.4.1 Evanescent Field . . . . . . . . . . . . . . . . . . . . . . . . 25 2.4.2 Double Clad Fiber Design . . . . . . . . . . . . . . . . . . . 26 2.5 Compositions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 2.6 Physical Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 2.6.1 Fiber Refractivehdex andCompositionProfile . . . . . . . 29 2.6.2 Strength and Reliability . . . . . . . . . . . . . . . . . . . . 30 2.6.3 Alternate Glass Host Fabrication . . . . . . . . . . . . . . . 30 3 COMPONENTS AND INTEGRATION 43 3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 3.2 Fiber Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 3.3 Fusion Splicing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 3.4 Pump and Signal Combiners . . . . . . . . . . . . . . . . . . . . . . 50 3.5 Isolators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 V vi CONTENTS 3.6 Circulators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 3.7 Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 3.8 Fiber Gratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 3.8.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 55 3.8.2 Applications of Bragg Gratings . . . . . . . . . . . . . . . . 57 3.8.3 Long Period Gratings . . . . . . . . . . . . . . . . . . . . . 59 3.9 Signal Multiplexers and Demultiplexers . . . . . . . . . . . . . . . . 61 3.10 Signal Add/Drop Components . . . . . . . . . . . . . . . . . . . . . 62 3.11 Dispersion Compensation Components . . . . . . . . . . . . . . . . 63 3.12 Integrated Components . . . . . . . . . . . . . . . . . . . . . . . . . 66 3.13 Pump Lasers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 4 RARE EARTH IONS INTRODUCTORY SURVEY 87 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 4.2 Atomic Physics of the Rare Earths . . . . . . . . . . . . . . . . . . . 87 4.2.1 Introduction The 4f Electron Shell . . . . . . . . . . . . . 87 4.2.2 The “Puzzle” of 4f Electron Optical Spectra . . . . . . . . . 91 4.2.3 Semiempirical Atomic and Crystal Field Hamiltonians . . . 92 4.2.4 Energy Level Fitting . . . . . . . . . . . . . . . . . . . . . . 94 4.3 Optical Spectra of Rare Earth Ions . . . . . . . . . . . . . . . . . . . 95 4.3.1 The Character of 4fN 4fN Optical Transitions . . . . . . . 95 4.3.2 Intensities of One-Photon Transitions Judd-Ofelt Theory . 96 4.4 Fundamental Properties . . . . . . . . . . . . . . . . . . . . . . . . 99 4.4.1 Transition Cross Sections . . . . . . . . . . . . . . . . . . . 99 4.4.2 Lifetimes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 4.4.3 Linewidths and Broadening . . . . . . . . . . . . . . . . . . 108 4.5 Spectroscopy of the Er3 Ion . . . . . . . . . . . . . . . . . . . . . 110 4.5.1 Lifetimes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 4.5.2 Er3 Spectra, Cross Sections, and Linewidths . . . . . . . . 114 4.6 ES -Er3 InteractionEffects . . . . . . . . . . . . . . . . . . . . . 120 5 ERBIUM-DOPED FIBER AMPLIFIERS AMPLIFIER BASICS 131 5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 5.2 Amplification in Three-Level Systems Basics . . . . . . . . . . . 131 5.2.1 Three-Level Rate Equations . . . . . . . . . . . . . . . . . . 131 5.2.2 The Overlap Factor . . . . . . . . . . . . . . . . . . . . . . 140 5.3 Reduction of the Three-Level System to the Two-Level System . . . 144 5.3.1 Validity of the Two-Level Approach . . . . . . . . . . . . . . 144 5.3.2 Generalized Rate Equations . . . . . . . . . . . . . . . . . . 146 5.4 Amplified Spontaneous Emission . . . . . . . . . . . . . . . . . . . 147 5.5 Analytical Solutions to the Two-Level System . . . . . . . . . . . . 149 6 ERBIUM-DOPED FIBER AMPLIFIERS .M ODELING AND COM- PLEX EFFECTS 153 6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153 6.2 Absorption and Emission Cross Sections . . . . . . . . . . . . . . . 153 CONTENTS vii 6.3 Gain and ASE Modeling . . . . . . . . . . . . . . . . . . . . . . . . 156 6.3.1 Model Equations - Homogeneous Broadening . . . . . . . . 156 6.3.2 Average Inversion Relationship . . . . . . . . . . . . . . . . 158 6.3.3 Inhomogeneous Broadening . . . . . . . . . . . . . . . . . . 159 6.4 Amplifier Simulations . . . . . . . . . . . . . . . . . . . . . . . . . 161 6.4.1 Signal Gain. ASE Generation, and Population Inversion . . . 161 6.4.2 Gain as a Function of Fiber Length . . . . . . . . . . . . . . 169 6.4.3 Spectral Profile of the ASE . . . . . . . . . . . . . . . . . . 169 6.4.4 Small Signal Spectral Gain andNoise Modeling . . . . . . . 171 6.4.5 Saturation Modeling Signal Gain and Noise Figure . . . . 173 6.4.6 Power Amplifier Modeling . . . . . . . . . . . . . . . . . . 175 6.4.7 Effective Parameter Modeling . . . . . . . . . . . . . . . . . 178 6.5 Transverse Mode Models Erbium Confinement Effect . . . . . . . 180 6.6 Excited State Absorption Effects . . . . . . . . . . . . . . . . . . . 186 6.6.1 Model Equations . . . . . . . . . . . . . . . . . . . . . . . . 186 6.6.2 Modeling Results in the Presence of ESA . . . . . . . . . . . 188 6.6.3 800 nm Band Pumping . . . . . . . . . . . . . . . . . . . . 188 6.7 EG -E$ InteractionEffects . . . . . . . . . . . . . . . . . . . . . 191 6.7.1 Upconversion Effects on Amplifier Performance . . . . . . . 193 6.7.2 Pair Induced Quenching . . . . . . . . . . . . . . . . . . . . 195 7 OPTICAL AMPLIFIERS IN FIBER OPTIC COMMUNICATION SYS- TEMS .TH EORY 201 7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201 7.2 Optical Noise: Device Aspects . . . . . . . . . . . . . . . . . . . . . 202 7.2.1 Classical Derivation of Optical Amplifier Noise . . . . . . . 202 7.2.2 Noise at the Output of an Optical Amplifier . . . . . . . . . . 205 7.2.3 Comparison of Optical Amplifier Devices . . . . . . . . . . 210 7.3 Optical Noise: System Aspects . . . . . . . . . . . . . . . . . . . . 212 7.3.1 Receivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213 7.3.2 Bit Error Rate Calculations .D irect Detection . . . . . . . . 214 7.3.3 Optical Preamplifiers - Noise Figure and Sensitivity . . . . . 220 7.3.4 Optical Inline Amplifiers .A mplifier Chains . . . . . . . . . 226 7.3.5 Noise in Optical Power Amplifiers . . . . . . . . . . . . . . 235 7.3.6 Nonlinearity Issues . . . . . . . . . . . . . . . . . . . . . . . 236 7.3.7 Analog Applications . . . . . . . . . . . . . . . . . . . . . . 240 8 AMPLIFIER CHARACTERIZATION AND DESIGN ISSUES 251 8.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251 8.2 Basic Amplifier Measurement Techniques . . . . . . . . . . . . . . . 251 8.2.1 Gain Measurements . . . . . . . . . . . . . . . . . . . . . . 251 8.2.2 Power Conversion Efficiency . . . . . . . . . . . . . . . . . 257 8.2.3 Noise Figure Measurements . . . . . . . . . . . . . . . . . . 258 8.3 Amplifier Design Issues . . . . . . . . . . . . . . . . . . . . . . . . 263 8.3.1 Copropagating and CounterpropagatingP umping Issues . . . 265 ... CONTENTS Vlll 8.3.2 Choice of Fiber Lengths and Geometries for Various Applica- tions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268 8.3.3 Multistage Amplifiers . . . . . . . . . . . . . . . . . . . . . 273 8.3.4 Bidirectional Amplifiers .................... 277 8.3.5 Power Amplifiers . . . . . . . . . . . . . . . . . . . . . . . 280 8.3.6 WDM Amplifier Design Issues . . . . . . . . . . . . . . . . 284 8.3.7 Distributed Amplifiers . . . . . . . . . . . . . . . . . . . . . 295 8.3.8 Waveguide Amplifiers . . . . . . . . . . . . . . . . . . . . . 302 9 SYSTEM IMPLEMENTATIONS OF AMPLIFIERS 321 9.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321 9.2 System Demonstrations and Issues . . . . . . . . . . . . . . . . . . . 323 9.2.1 Preamplifiers . . . . . . . . . . . . . . . . . . . . . . . . . . 323 9.2.2 Inline Amplifiers - Single ChannelTransmission . . . . . . . 327 9.2.3 Inline Amplifiers - WDM Transmission . . . . . . . . . . . . 335 9.2.4 Repeaterless Systems ..................... 345 9.2.5 Remote Pumping . . . . . . . . . . . . . . . . . . . . . . . . 346 9.2.6 Analog Applications . . . . . . . . . . . . . . . . . . . . . . 351 9.2.7 Gain Peaking and Self-Filtering . . . . . . . . . . . . . . . . 354 9.2.8 Polarization Issues . . . . . . . . . . . . . . . . . . . . . . . 359 9.2.9 Transient Effects . . . . . . . . . . . . . . . . . . . . . . . . 363 9.3 Soliton Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367 9.3.1 Principles . . . . . . . . . . . . . . . . . . . . . . . . . . . 367 9.3.2 System Results and Milestones . . . . . . . . . . . . . . . . 374 10 FOUR LEVEL FIBER AMPLIFIERS FOR 1.3 M AMPLIFICATION 401 10.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 401 10.1.1 Gain in a Four-Level System . . . . . . . . . . . . . . . . . 401 10.2 P? -doped Fiber Amplifiers . . . . . . . . . . . . . . . . . . . . . . 404 10.2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 404 10.2.2 Spectroscopic Properties . . . . . . . . . . . . . . . . . . . . 405 10.2.3 Gain Results for P? -doped Fiber Amplifiers . . . . . . . . 406 10.2.4 ModelingoftheP? -dopedFiberAmplifierGain . . . . . 412 10.2.5 System Results . . . . . . . . . . . . . . . . . . . . . . . . . 416 10.3 Nd3 -Doped Fiber Amplifiers . . . . . . . . . . . . . . . . . . . . . 418 10.3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 418 10.3.2 Gain Results for Nd3 -Doped Fiber Amplifiers . . . . . . . . 419 10.3.3 ModelingoftheNd3 -DopedFiberAmplifierGain . . . . . 420 Appendix A 429 A .1 OASIX " " Amplifier Simulation Software . . . . . . . . . . . . . . . 429 A.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 429 A.2.1 System Requirements . . . . . . . . . . . . . . . . . . . . . 429 A.2.2 Installing OASIX" . . . . . . . . . . . . . . . . . . . . . . . 430 A.2.3 Starting OASM" . . . . . . . . . . . . . . . . . . . . . . . . 430 A.2.4 What to do next . . . . . . . . . . . . . . . . . . . . . . . . 430 CONTENTS ix A.3 A Quick Overview and Tour . . . . . . . . . . . . . . . . . . . . . . 430 A.3.1 Fibers and Modeling Parameters . . . . . . . . . . . . . . . 430 A.3.2 Saving a Simulation Configuration . . . . . . . . . . . . . . 431 A.3.3 Device Types Simulated . . . . . . . . . . . . . . . . . . . . 431 A.3.4 Data Entry and Device Conventions . . . . . . . . . . . . . . 432 A.3.5 Screens and Menus ...................... 432 A.3.6 Simulation Looping and Output Modes . . . . . . . . . . . . 433 A.4 Screen Contents and Simulation Methodology . . . . . . . . . . . . 434 A.4.1 Main/Entry Screen . . . . . . . . . . . . . . . . . . . . . . . 434 A.4.2 Single-Stage Setup Screen . . . . . . . . . . . . . . . . . . . 435 A.4.3 Additional Signals Screen . . . . . . . . . . . . . . . . . . . 435 A.4.4 Output Setup Screen . . . . . . . . . . . . . . . . . . . . . . 436 A.4.5 Simulation Status Box . . . . . . . . . . . . . . . . . . . . . 437 AS Simulation Looping Structure . . . . . . . . . . . . . . . . . . . . . 438 AS. 1 Specifying Loop Parameters . . . . . . . . . . . . . . . . . . 438 A.5.2 Choosing Loop Order . . . . . . . . . . . . . . . . . . . . . 438 . . . . . . . . . . . . . . . . A.5.3 Linear or Logarithmic Looping 439 A.5.4 Multiple Parameters Varied in a Loop . . . . . . . . . . . . . 439 A.5.5 Influence on Output Format . . . . . . . . . . . . . . . . . . 440 A.5.6 Output Modes ......................... 440 A.6 Sample Simulations . . . . . . . . . . . . . . . . . . . . . . . . . . 442 A.6.1 Single-Run, Single-Stage EDFA . . . . . . . . . . . . . . . . 442 A.6.2 Multiple-Run, Single-Stage EDFA . . . . . . . . . . . . . . 443 A.6.3 Other simulations to try . . . . . . . . . . . . . . . . . . . . 443 A.7 Computation of Signal Related Quantities . . . . . . . . . . . . . . . 443 A.8 Computation of ASE Related Quantities . . . . . . . . . . . . . . . . 444 A.9 Basic Operating Principles . . . . . . . . . . . . . . . . . . . . . . . 445 A.9.1 Simulation Speed and the Number of Waves . . . . . . . . . 446 A.9.2 Causes and Remedies for Convergence Failure . . . . . . . . 447 A.10 Comment on the treatment of losses . . . . . . . . . . . . . . . . . . 448 INDEX 451
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