Spie Press BookOptical Communication Receiver Design
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We are surrounded by an ongoing revolution in optical communication. Fiber-optic networks carrying gigabits per second span oceans and continents, and devices such as optical amplifiers, which were once regarded only as laboratory curiosities, are now commonplace. The vast capacity of optical communication systems has enabled the development of information infrastructures of both national and global extent. Optical communication techniques are not restricted to fiber-optics. Free-space optical communication offers the possibility of high-data-rate links among satellites and the Earth, allowing even greater flexibility in terms of network connectivity and access.
This text provides an overview of the design principles for receivers used in optical communication systems. The technology and techniques that are discussed are similar to those used in conventional microwave communication receivers; however, there are also significant differences because of the unique characteristics of the photodetection process. The text grew out of the notes for a short course in receiver design. The level of the material is targeted at the practicing engineer and the text contains some 500 references to provide a reader with pointers to the wide variety of work that is available in the open literature.
The material is organized into seven chapters, with Chapter 1 providing a brief review of the technologies used to construct optical communication links. Following the technology introduction, Chapter 2 illustrates the flow of system performance specifications into receiver requirements and is illustrated by the use of system link and receiver sensitivity budgets. Chapter 3 introduces the fundamentals of photodetection and the associated statistics. Semi-classical techniques are used, with appropriate references to quantum mechanical considerations as needed. The signal-to-noise ratio for both direct and coherent detection receivers is derived and the concept of a shot-noise-limited receiver is introduced. The characteristics and performance of photodetectors are reviewed in Chapter 4. The p-i-n, avalanche photodiode, and metal-semiconductor-metal photodetectors are covered in detail and a series of equivalent circuit models are developed so that the impact of device characteristics on achievable receiver performance can be determined.
The circuit analysis techniques used with electrical noise are omitted in many engineering curricula, and Chapter 5 provides a quick tutorial on the general subject of noise analysis and also serves to describe the specific analysis techniques needed to model optical receivers. In particular, we illustrate the concept of an equivalent input current-noise model for the receiver. Chapter 6 reviews the design of the receiver front end, covering the resistor terminated voltage amplifier, high-impedance amplifier, and transimpedance amplifier. Chapter 7 concludes the text with examples of receiver performance analysis. Direct detection, coherent detection, and optically preamplified receivers are discussed, as well as analog systems. Particular attention is given to the detection statistics associated with the various photodetectors and receiver structures.