An up-to-date, comprehensive guide for advanced electrical engineering studentsand electrical engineers working in the IC and optical industries
This book covers the major transimpedance amplifier (TIA) topologies and their circuit implementations for optical receivers. This includes the shunt-feedback TIA, common-base TIA, common-gate TIA, regulated-cascode TIA, distributed-amplifier TIA, nonresistive feedback TIA, current-mode TIA, burst-mode TIA, and analog-receiver TIA. The noise, transimpedance, and other performance parameters of these circuits are analyzed and optimized. Topics of interest include post amplifiers, differential vs. single-ended TIAs, DC input current control, and adaptive transimpedance. The book features real-world examples of TIA circuits for a variety of receivers (direct detection, coherent, burst-mode, etc.) implemented in a broad array of technologies (HBT, BiCMOS, CMOS, etc.).
The book begins with an introduction to optical communication systems, signals, and standards. It then moves on to discussions of optical fiber and photodetectors. This discussion includes p-i-n photodetectors; avalanche photodetectors (APD); optically preamplified detectors; integrated detectors, including detectors for silicon photonics; and detectors for phase-modulated signals, including coherent detectors. This is followed by coverage of the optical receiver at the system level: the relationship between noise, sensitivity, optical signal-to-noise ratio (OSNR), and bit-error rate (BER) is explained; receiver impairments, such as intersymbol interference (ISI), are covered. In addition, the author presents TIA specifications and illustrates them with example values from recent product data sheets. The book also includes:
* Many numerical examples throughout that help make the material more concrete for readers
* Real-world product examples that show the performance of actual IC designs
* Chapter summaries that highlight the key points
* Problems and their solutions for readers who want to practice and deepen their understanding of the material
* Appendices that cover communication signals, eye diagrams, timing jitter, nonlinearity, adaptive equalizers, decision point control, forward error correction (FEC), and second-order low-pass transfer functions
Analysis and Design of Transimpedance Amplifiers for Optical Receivers belongs on the reference shelves of every electrical engineer working in the IC and optical industries. It also can serve as a textbook for upper-level undergraduates and graduate students studying integrated circuit design and optical communication.
EDUARD SÄCKINGER, PhD, is Principal Analog Engineer at MACOM Technology Solutions, USA.For more than ten years, Dr. Säckinger worked at Bell Laboratories (AT&T and Lucent Technologies). After that, he joined Agere Systems (a Lucent spin-off), Conexant Systems, and Ikanos Communications (through an acquisition). He has conducted seminars on broadband circuits for optical fiber communication at Agere Systems, Lucent Technologies, MEAD Microelectronics, and the VLSI Symposium. He served as an Associate Editor for IEEE Journal of Solid-State Circuits for six years. He is the author of the book Broadband Circuits for Optical Fiber Communication.
Transimpedance amplifiers (TIA) are used at the front end of optical receivers. They can also be found at the front end of read circuits for optical storage systems and laser RADAR systems for distance measurement. But TIAs are not limited only to optical applications; particle/radiation detector chips, vision sensor chips, biological sensor chips, motion sensors in microelectromechanical systems, and wideband radio receivers also make use of TIAs.
This broad range of applications is not surprising. The TIA is essentially a sensitive and fast current measurement device: A weak current signal, typically originating from a sensor such as a photodetector, a particle/radiation detector, a biological sensor electrode, a MEMS electrostatic transducer, or a radio receiver antenna, is amplified and converted into a voltage signal. The term transimpedance derives from the older term transfer impedance, which indicates that an input current at one port is producing an output voltage at another port.
The term transimpedance amplifier may evoke the image of a voltage amplifier with a shunt-feedback resistor. However, this is just one particular implementation. Several other topologies exist and novel TIA circuits are still being invented today. Each circuit presents a different trade-off between sensitivity (noise), speed (bandwidth), power, area, and other performance measures. With each application having its own set of requirements, different applications benefit from different circuit designs.
Chapters 1-4 provide background information on optical communication. This part of the book establishes useful context for the later chapters on TIA design. Readers who are not interested in optical applications may skip over much of this material.
Chapter 1 describes the components that make up conventional and digital coherent optical receivers and transmitters. Common modulation formats (NRZ, RZ, 4-PAM, QPSK, SCM, etc.), modulation codes, transmission modes (continuous mode and burst mode), and standards are introduced.
Chapter 2 is about the communication channel presented by the optical fiber. Its loss, bandwidth, various forms of dispersion, and nonlinearities are described. The compensation of loss and dispersion and the mitigation of nonlinear effects are discussed briefly.
Chapter 3 covers the relevant photodetectors. The responsivity, bandwidth, and noise properties of the p-i-n photodetector, the avalanche photodetector (APD), and the optically preamplified p-i-n detector are examined. Then, integrated detectors including detectors for silicon photonics are covered. Finally, detectors for phase-modulated signals (QPSK, DQPSK, etc.) including the coherent detector with phase and polarization diversity are discussed.
Chapter 4 deals with the receiver at the system level. An analysis of how noise in the receiver causes bit errors leads to the definition of the receiver sensitivity in unamplified transmission systems and the required optical signal-to-noise ratio (required OSNR) in amplified transmission systems. Power penalties due to receiver impairments, such as intersymbol interference (ISI), are discussed. An analysis of the trade-off between noise and ISI leads to recommendations for the receiver's bandwidth and frequency response.
The remainder of the book focuses on the analysis and design of TIAs.
Chapter 5 introduces the main specifications, such as the transimpedance, bandwidth, phase linearity, group-delay variation, jitter, input-referred noise current, maximum input current, and crosstalk. The measurement of some key parameters is discussed. Example values from recent product data sheets are given to illustrate the specifications.
Chapter 6 covers the popular shunt-feedback TIA in detail. The transimpedance, input impedance, and output impedance are calculated. The stability and the transimpedance limit of single and multistage implementations are analyzed. The noise performance of TIAs with FET and BJT front ends are derived. Ogawa's noise factor and its relationship to induced gate noise is explained. Then, the noise optimization of TIAs with FET and BJT front ends by means of device sizing and biasing is discussed. The impact of constraints, such as a constant gain-bandwidth product, on the noise optimum is examined. Finally, noise matching networks and their properties are investigated.
Chapter 7 extends the basic shunt-feedback TIA with practical features such as a postamplifier, differential inputs and outputs, DC input current control, and adaptive transimpedance. Then, the chapter turns to alternative TIA topologies such as the common-base TIA, common-gate TIA, the regulated-cascode TIA, and the distributed-amplifier TIA.
Chapter 8 examines additional TIA circuit techniques such as capacitive feedback, optical feedback, active feedback, current mode, and photodetector bootstrapping. Then, the chapter turns to TIAs for specialized applications, namely burst-mode TIAs (e.g., for passive optical networks) and analog-receiver TIAs (e.g., for hybrid fiber-coax networks or microwave photonic links).
Chapter 9 discusses published circuit examples in a variety of technologies (BJT, HBT, BiCMOS, CMOS, MESFET, and HFET) illustrating and solidifying the concepts covered in the earlier chapters. The chapter concludes with a list of recent TIA publications.
A number of appendices cover subjects related to, but not limited to, the design of optical receivers and TIAs.
Appendix A reviews the power spectral density, bandwidth, and signal-to-noise requirements of some common communication signals (NRZ, RZ, 4-PAM, CATV).
Appendix B discusses eye diagrams, eye openings, and eye margins, including their measurement and simulation.
Appendix C deals with data and clock jitter. The terminology and the measurement of jitter is discussed and the relationship between jitter, phase noise, and bit-error rate is explained.
Appendix D reviews nonlinearity and the resulting signal distortions, which are important in systems that perform linear signal processing (equalization, data conversion, etc.) and in applications that use higher-order or multicarrier modulation.
Appendix E provides an introduction to adaptive equalization. The basics of the feedforward equalizers (FFEs) and decision-feedback equalizers (DFEs) are covered.
Appendix F briefly discusses adaptive control of the decision threshold and sampling instant.
Appendix G provides an introduction to forward error correction (FEC).
Appendix H discusses second-order low-pass transfer functions, which are important for the analysis of TIAs. The frequency response, bandwidth, noise bandwidth, phase linearity, group-delay variation, overshoot, and jitter are covered.
Appendix I provides answers to all the end-of-chapter problems. This appendix also serves as a repository for additional material, such as derivations and generalizations, that would be too distracting to present in the main text.
It is assumed that the reader is familiar with basic analog IC design as presented, for example, in Analysis and Design of Analog Integrated Circuits by Gray et al.  or a similar book [2-4].
The book is written from the perspective of an electrical engineer. For example, whenever possible we use voltages and currents rather than abstract variables, we use one-sided power spectral densities as they would appear on a spectrum analyzer, we prefer the use of noise bandwidths over Personick integrals, and so forth. Examples are given frequently to make the material more concrete. Many problems, together with their answers, are provided for readers who want to practice and deepen their understanding of the learned material.
I hope this book will be useful to upper-level undergraduates and graduate-level students in integrated circuit design and optical communication. Professionals in the IC and optical industry may find this book to be a valuable reference as well.
This book grew out of an effort to make a second edition of my earlier book Broadband Circuits for Optical Fiber Communication . As I was reworking chapter by chapter, covering new developments, treating subjects in more depth, and so forth, the length of each chapter doubled or tripled. For this reason, it became impractical to cover all the subjects of the original book in a single book. The present book covers the material from Chapters 1 to 5 of the original book.
I would like to thank all my colleagues at the Bell Laboratories (first of AT&T and then of Lucent Technologies), Agere Systems, Conexant, and Ikanos Communications from whom I have learned so much.
I am deeply indebted to the reviewers who have given freely of their time to read through the book, in part or in full. In particular, I am most grateful to Dr. Ricardo Aroca, Acacia Communications; Mr. Henry M. Daghighian, Finisar Corporation; Dr. Christopher Doerr, Acacia Communications; Dr. Yuriy M. Greshishchev, Ciena Corporation; Prof. Dan Li, Jiaotong University, Xi'an; Dr. Sunderarajan Mohan, Synopsys Inc.; Prof. Sung-Min Park, Ewha Women's University, Seoul; and Prof. Sorin Voinigescu, University of Toronto.
Despite the efforts made, there are undoubtedly some mistakes left in this book. If you have any corrections or suggestions, please e-mail them to email@example.com. Thank you!