Fiber Optics Engineering

Transcription

1 Fiber Optics Engineering For further volumes:

2 Optical Networks Series Editor: Biswanath Mukherjee University of California, Davis Davis, CA

3 Mohammad Azadeh Fiber Optics Engineering 123

4 Mohammad Azadeh Source Photonics, Inc Nordhoff St. Chatsworth, CA USA Series Editor Biswanath Mukherjee University of California Davis, CA USA ISSN ISBN e-isbn DOI / Springer Dordrecht Heidelberg London New York Library of Congress Control Number: c Springer Science+Business Media, LLC 2009 All rights reserved. This work may not be translated or copied in whole or in part without the written permission of the publisher (Springer Science+Business Media, LLC, 233 Spring Street, New York, NY 10013, USA), except for brief excerpts in connection with reviews or scholarly analysis. Use in connection with any form of information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed is forbidden. The use in this publication of trade names, trademarks, service marks, and similar terms, even if they are not identified as such, is not to be taken as an expression of opinion as to whether or not they are subject to proprietary rights. Printed on acid-free paper Springer is part of Springer Science+Business Media (

5 Preface Within the past few decades, information technologies have been evolving at a tremendous rate, causing profound changes to our world and our ways of life. In particular, fiber optics has been playing an increasingly crucial role within the telecommunication revolution. Not only most long-distance links are fiber based, but optical fibers are increasingly approaching the individual end users, providing wide bandwidth links to support all kinds of data-intensive applications such as video, voice, and data services. As an engineering discipline, fiber optics is both fascinating and challenging. Fiber optics is an area that incorporates elements from a wide range of technologies including optics, microelectronics, quantum electronics, semiconductors, and networking. As a result of rapid changes in almost all of these areas, fiber optics is a fast evolving field. Therefore, the need for up-to-date texts that address this growing field from an interdisciplinary perspective persists. This book presents an overview of fiber optics from a practical, engineering perspective. Therefore, in addition to topics such as lasers, detectors, and optical fibers, several topics related to electronic circuits that generate, detect, and process the optical signals are covered. In other words, this book attempts to present fiber optics not so much in terms of a field of optics but more from the perspective of an engineering field within optoelectronics. As a result, practicing professionals and engineers, with a general background in physics, electrical engineering, communication, and hardware should find this book a useful reference that provides a summary of the main topics in fiber optics. Moreover, this book should be a useful resource for students whose field of study is somehow related to the broad areas of optics, optical engineering, optoelectronics, and photonics. Obviously, covering all aspects of fiber optics in any depth requires many volumes. Thus, an individual text must out of necessity be selective in the topics it covers and in the perspectives it offers. This book covers a range of subjects, starting from more abstract basic topics and proceeding towards more practical issues. In most cases, an overview of main results is given, and additional references are provided for those interested in more details. Moreover, because of the practical character of the book, mathematical equations are kept at a minimum, and only essential equations are provided. In a few instances where more mathematical details are given and equations are derived, an elementary knowledge of calculus is sufficient for following the discussion, and the inconvenience of having to go through the math is well rewarded by the deeper insights provided by the results. The logical flow of the book is as follows. The first three chapters act as a foundation and a general background for the rest of the book. Chapter 1 covers basic physical concepts such as the nature of light, electromagnetic spectrum, and a brief overview of fiber optics. Chapter 2 provides an overview of important networking concepts and the role of fiber optics within the telecommunication infrastruc-

6 vi Preface ture. Chapter 3 provides an introduction to fiber optics from a signal viewpoint. This includes some basic mathematical background, as well as characterization of physical signals in the electrical and optical domains. Chapters 4 7 cover the main elements of a fiber optic link in more depth. Chapter 4 is dedicated to diode lasers which are the standard source in fiber optics. Chapter 5 deals with propagation of optical signals in fibers and signal degradation effects. PIN and APD detectors that convert photons back to electrons are the topic of Chapter 6. Thus, these three chapters deal with generation, propagation, and detection of optical signals. Chapter 7, on the other hand, deals with light coupling and passive components. Therefore, Chapter 7 examines ways of transferring optical signals between elements that generate, detect, and transport the optical signals. The next two chapters, Chapters 8 and 9, essentially deal with electronic circuits that interface with diode lasers and optical detectors. In particular, Chapter 8 examines optical transmitter circuits and various electronic designs used in driving highspeed optical sources. Chapter 9 examines the main blocks in an optical receiver circuit as well as ways of characterizing the performance of a receiver. A feature of this book is that in addition to traditional CW transceivers, burst mode transmitter and receiver circuits, increasingly used in PON applications, are also discussed. The final three chapters of the book cover areas that have to do with fiber optics as a viable industry. Chapter 10 presents an overview of reliability issues for optoelectronic devices and modules. A viable fiber optic system is expected to operate outside the laboratory and under real operating conditions for many years, and this requires paying attention to factors outside pure optics or electronics. Chapter 11 examines topics related to test and measurement. In an engineering environment, it is crucial not only to have a firm grasp on theoretical issues and design concepts, but also to design and conduct tests, measure signals, and use test instruments effectively. Finally, Chapter 12 presents a brief treatment of fiber optic related standards. Standards play a crucial rule in all industries, and fiber optics is no exception. Indeed, it is oftentimes adherence to standards that enables a device or system to go beyond a laboratory demonstration and fulfill a well-defined role in the jigsaw of a complex industry such as fiber optics. * * * I am greatly indebted to many individuals for this project. In particular, I would like to thank Dr. A. Nourbakhsh who inspired and encouraged me to take on this work. I would also like to acknowledge my past and present colleagues at Source Photonics for the enriching experience of many years of working together. In particular, I would like to thank Dr. Mark Heimbuch, Dr. Sheng Zheng, Dr. Near Margalit, Dr. Chris LaBounty, and Dr. Allen Panahi, for numerous enlightening discussions on a variety of technical subjects. Without that experience and those discussions, this book could not have been created. I would also like to thank Springer for accepting this project, and in particular Ms. Katelyn Stanne, whose guidance was essential in bringing the project to its conclusion. Mohammad Azadeh

7 Contents Chapter 1 Fiber Optic Communications: A Review Introduction The nature of light The wave nature of light The particle nature of light The wave particle duality The electromagnetic spectrum Elements of a fiber optic link Light sources, detectors, and glass fibers Optical sources Optical detectors The optical fiber Advantages of fiber optics Digital and analog systems Characterization of fiber optic links Summary Chapter 2 Communication Networks Introduction Network topologies Telecommunication networks Networking spans Local area networks (LANs) Metropolitan area networks (MANs) Wide area networks (WANs) Hierarchical structure of networks Open System Interconnect (OSI) model Datalink layer Network layer Higher layers Circuit switching and packet switching networks Circuit switching Packet switching SONET/SDH WDM networks Passive optical networks (PONs) Summary Chapter 3 Signal Characterization and Representation Introduction Signal analysis Fourier transform Fourier analysis and signal representation

8 viii Contents Digital signals, time and frequency domain representation Non-return-to-zero (NRZ) and pseudorandom (PRBS) codes Random and pseudo-random signals in frequency domain High-speed electrical signals Lumped and distributed circuit models Transmission lines Characteristic impedance Microstrip and striplines Differential signaling Optical signals Average power Eye diagram representation Amplitude parameters Time parameters Eye pattern and bathtub curves Spectral characteristics of optical signals Single-mode signals Multimode signals Summary Chapter 4 Semiconductor Lasers Introduction Optical gain and optical oscillation Physical processes for optical amplification Optical amplification in semiconductors Rate equation approximation Carrier density rate equation Photon density rate equation Steady-state analysis Temperature dependence of LI curve Small signal frequency response Time response Frequency chirp Large signal behavior Semiconductor laser structures Heterostructure laser Quantum well lasers Distributed feedback (DFB) lasers Vertical surface emitting lasers (VCSELs) Summary Chapter 5 Optical Fibers Introduction Optical fiber materials, structure, and transmission windows Guided waves in fibers

9 Contents ix Guided modes, ray description Guided modes, wave description Signal degradation in optical fibers Attenuation Absorption Scattering Dispersion Modal dispersion Chromatic dispersion Waveguide dispersion Polarization dispersion Nonlinear effects in fibers Self- and cross-phase modulation (SPS and XPM) Four Wave Mixing (FWM) Stimulated Raman scattering (SRS) Stimulated Brillouin Scattering (SBS) Fiber amplifiers Summary Chapter 6 PIN and APD Detectors Introduction The PIN diode and photon-electron conversion PIN diode, static characteristics PIN diode, dynamic characteristics Avalanche photodiode (APD) Noise in photodetectors Shot noise Thermal noise Signal-to-noise ratio (SNR) Photodetector materials and structures Photodetector materials PIN diode structures APD structures Summary Chapter 7 Light Coupling and Passive Optical Devices Introduction Coupling light to and from a fiber Direct coupling Lensed fibers Fiber coupling via lens Fiber-to-fiber coupling Connectorized couplings Fiber finish Fiber splicing

10 x Contents 7.4 Passive components Splitters and couplers Attenuators Isolators Optical filters Summary Chapter 8 Optical Transmitter Design Introduction Transmitter optical subassembly (TOSA) Biasing the laser: the basic LI curve Average power control (APC) Open loop average power control schemes Closed loop power control Thermal runaway Modulation circuit schemes Basic driver circuit Transmission line effects Differential coupling High current drive circuits: ac coupling Modulation control, open loop vs. closed loop schemes Open loop modulation control Closed loop modulation control: Pilot tone Closed loop modulation control: high bandwidth control External modulators and spectral stabilization Burst mode transmitters Analog transmitters High frequency design practices Power plane Circuit layout Summary Chapter 9 Optical Receiver Design Introduction Receiver optical subassembly (ROSA) Transimpedance amplifier (TIA) Detector/TIA wire bonding in optical subassemblies APD receivers Limiting amplifier Clock and data recovery Performance of optical receivers Signal-to-noise ratio (SNR) and bit error rate (BER) Sensitivity Overload Characterization of clock and data recovery circuits

11 Contents xi Jitter transfer Jitter tolerance Burst mode receivers Dynamic range challenges in burst mode traffic Design approaches for threshold extraction Burst mode TIAs Summary Chapter 10 Reliability Introduction Reliability, design flow, and design practices Design flow Modular approach Reliability design practices and risk areas Electrical issues Design margin Printed circuit boards (PCBs) Component selection Protective circuitry Optical issues Device level reliability Optical subassemblies Optical fibers and optical coupling Thermal issues Power reduction Thermal resistance Mechanical issues Shock and vibration Thermal induced mechanical failures Mechanical failure of fibers Software issues Software reliability Failure rate reduction Reliability quantification Statistical models of reliability: basic concepts Failure rates and MTTF Activation energy Summary Chapter 11 Test and Measurement Introduction Test and measurement: general remarks Optical power Optical waveform measurements Electrical oscilloscopes with optical to electrical converter...301

12 xii Contents Digital communication analyzers (DCA) Amplitude related parameters Time-related parameters Mask measurement Spectral measurements Optical spectrum analyzer (OSA) Wavelength meters Link performance testing Bit error rate tester (BERT) Sensitivity measurement Sensitivity penalty tests Analog modulation measurements Lightwave signal analyzer (LSA) Signal parameter measurements Summary Chapter 12 Standards Introduction Standards development bodies International Telecommunication Union (ITU) International Electrotechnical Commission (IEC) Institute of Electrical and Electronics Engineers (IEEE) Telecommunication Industry Association (TIA) ISO and ANSI Telcordia (Bellcore) Miscellaneous organizations Standards classification and selected lists Standards related to components Standards related to measurements and procedures Reliability and safety standards Networking and system standards Fiber standards Laser safety SFF-8472 digital monitoring interface Identification data (A0h) Diagnostic data (A2h) Reliability standards Networking standards SONET/SDH Ethernet Passive optical networks (PON) Summary Appendix A Common Acronyms Appendix B Physical Constants Index