Library of Congress Cataloging-in-Publication Data

Paschotta, Rüdiger.

Field guide to optical fiber technology / Rudiger Paschotta.

p. cm. -- (The field guide series)

Includes bibliographical references and index.

ISBN 978-0-8194-8090-3

1. Fiber optics. 2. Optical fibers. I. Title.

TA1800.P356 2009

621.36'92--dc22

2009049649

Published by

SPIE

P.O. Box 10

Bellingham, Washington 98227-0010 USA

Phone: +1 360 676 3290

Fax: +1 360 647 1445

E-mail: books@spie.org

Web: http://spie.org

The content of this book reflects the work and thought of the author. Every effort has been made to publish reliable and accurate information herein, but the publisher is not responsible for the validity of the information or for any outcomes resulting from reliance thereon.

Printed in the United States of America.

Introduction to the Series

Welcome to the SPIE Field Guides—a series of publications written directly for the practicing engineer or scientist. Many textbooks and professional reference books cover optical principles and techniques in depth. The aim of the SPIE Field Guides is to distill this information, providing readers with a handy desk or briefcase reference that provides basic, essential information about optical principles, techniques, or phenomena, including definitions and descriptions, key equations, illustrations, application examples, design considerations, and additional resources. A significant effort will be made to provide a consistent notation and style between volumes in the series.

Each SPIE Field Guide addresses a major field of optical science and technology. The concept of these Field Guides is a format-intensive presentation based on figures and equations supplemented by concise explanations. In most cases, this modular approach places a single topic on a page, and provides full coverage of that topic on that page. Highlights, insights, and rules of thumb are displayed in sidebars to the main text. The appendices at the end of each Field Guide provide additional information such as related material outside the main scope of the volume, key mathematical relationships, and alternative methods. While complete in their coverage, the concise presentation may not be appropriate for those new to the field.

The SPIE Field Guides are intended to be living documents. The modular page-based presentation format allows them to be easily updated and expanded. We are interested in your suggestions for new Field Guide topics as well as what material should be added to an individual volume to make these Field Guides more useful to you. Please contact us at fieldguides@SPIE.org.

John E. Greivenkamp, Senas Editor

College of Optical Sciences

The University of Arizona

The Field Guide Series

The Field Guide Series

Keep information at your fingertips with all of the titles in the Field Guide series:

Field Guide to Geometrical Optics, John E. Greivenkamp (FG01)

Field Guide to Atmospheric Optics, Larry C. Andrews (FG02)

Field Guide to Adaptive Optics, Robert K. Tyson & Benjamin W. Frazier (FG03)

Field Guide to Visual and Ophthalmic Optics, Jim Schwiegerling (FG04)

Field Guide to Polarization, Edward Collett (FG05)

Field Guide to Optical Lithography, Chris A. Mack (FG06)

Field Guide to Optical Thin Films, Ronald R. Willey (FG07)

Field Guide to Spectroscopy, David W. Ball (FG08)

Field Guide to Infrared Systems, Arnold Daniels (FG09)

Field Guide to Interferometric Optical Testing, Eric P. Goodwin & James C. Wyant (FG10)

Field Guide to Illumination, Angelo V. Arecchi; Tahar Messadi; R. John Koshel (FG11)

Field Guide to Lasers, Rüdiger Paschotta (FG12)

Field Guide to Microscopy, Tomasz Tkaczyk (FG13)

Field Guide to Laser Pulse Generation, Rüdiger Paschotta (FG14)

Field Guide to Infrared Systems, Detectors, and FPAs, Second Edition, Arnold Daniels (FG15)

Field Guide to Optical Fiber Technology

Fiber optics have become one of the essential elements of modern optical technology. Early work has mostly focused on the transmission of light over long distances, particularly for use in optical fiber communications. Further work has greatly expanded the application areas of optical fibers, which now also include fields like fiber amplifiers, fiber lasers, supercontinuum generation, pulse compression, and fiber-optic sensors. This diversity of applications has been enabled by a variety of types of optical fibers, which can greatly differ in many respects.

This Field Guide provides an overview of optical fiber technology. It not only describes many different types of fibers and their properties, but also presents in a compact form the relevant physical foundations. Sophisticated mathematics, e.g., concerning fiber modes, are not included, as such issues are covered in detail by several textbooks. Both passive and active (amplifying) fibers are discussed, and an overview on fiber nonlinearities and the application of active fibers in amplifiers and lasers is included. The large bibliography contains many useful references, covering both pioneering work and later seminal articles and books. This Guide should be very useful for a wide audience, including practitioners in industry as well as researchers.

I am greatly indebted to my wife, Christine, who strongly supported the creation of this Field Guide by improving most of the figures.

Dr. Rüdiger Paschotta

RP Photonics Consulting GmbH

Zürich, Switzerland

Table of Contents

Glossary of Symbols ix

Basics of Fibers 1

Principle of Waveguiding 1

Wave Propagation in Fibers 2

Calculation of Fiber Modes 3

Decomposition into Modes 5

Types of Fiber Modes 6

Cladding Modes 7

Step-Index Fibers 8

Single-Mode Fibers 9

V Number of a Single-Mode Fiber 10

Numerical Aperture of a Single-Mode Fiber 11

Effective Mode Area 12

Multimode Fibers 14

Glass Fibers 17

Non-Silica Glass Fibers 18

Nanofibers 19

Plastic Optical Fibers 20

Origins of Propagation Losses 21

Losses of Silica Fibers 22

Bend Losses 23

Chromatic Dispersion 24

Birefringence and Polarization Effects 29

Polarization-Maintaining Fibers 30

Nonlinear Effects in Fibers 32

Overview on Fiber Nonlinearities 32

Effects of the Kerr Nonlinearity 33

Self-Phase Modulation 34

Numbers on Fiber Nonlinearities 36

Soliton Pulses 37

Linear Pulse Compression 39

Nonlinear Pulse Compression 40

Cross-Phase Modulation 43

Four-Wave Mixing 44

Parametric Amplification 45

Raman Scattering 46

Brillouin Scattering 48

Passive Fibers for Data Transmission 49

Wavelength Regions for Data Transmission 49

Optimization of Telecom Fibers 50

Considerations on Chromatic Dispersion 51

Dispersion Compensation 52

Important Standards for Telecom Fibers 53

Polarization Mode Dispersion 54

Photonic Crystal Fibers 55

Introduction to Photonic Crystal Fibers 55 Guidance According to Average Refractive Index 56

Fibers with Large Air Holes 57

Photonic Bandgap Fibers 58

Birefringent PCFs 59

Large Mode Area Fibers 60

Large Mode Area Fibers 60

Other Solid-Core Fiber Designs 61

Photonic Crystal Fiber Designs 62

Using Passive Optical Fibers 63

Tolerances for Low-Loss Fiber Joints 64

Launching Light into Single-Mode Fibers 65

Preparing Fiber Ends 66

Fusion Splicing 67

Fiber Connectors 68

Passive Fiber-Optic Components 69

Fiber Couplers 69

Fiber Bragg Gratings 70

Fiber-Coupled Faraday Isolators 72

Fiber Polarization Controllers 73

Active Fiber Devices 74

Rare-Earth-Doped Fibers 74

Importance of the Host Glass 75

Common Host Glasses 76

Double-Clad Fibers 77

Pump Absorption in Double-Clad Fibers 79

Coreless End Caps 80

Amplified Spontaneous Emission 81

Erbium-Doped Fiber Amplifiers 83 Neodymium- and Ytterbium-Doped Amplifiers 84

High-Power Fiber Amplifiers 85

Gain Efficiency 86

Gain Saturation 88

Continuous-Wave Fiber Lasers 90

High-Power Lasers vs. MOPAs 91

Upconversion Fiber Lasers 92

Pulsed Fiber Lasers 93

Mode-Locked Fiber Lasers 94

Equation Summary 96

Bibliography 101

Index 113