Optical Receivers The role of an optical receiver is to convert the optical signal back into electrical form and recover the data transmitted through the lightwave system. Its main component is a photodetector that converts light into electricity through the photoelectric effect. The requirements for a photodetector are similar to those of an optical source. It should have high sensitivity, fast response, low noise, low cost, and high reliability. Its size should be compatible with the fiber-core size. These requirements are best met by photodetectors made of semiconductor materials. This chapter focuses on photodetectors and optical receivers [1]–[9]. We introduce in. | Fiber-Optic Communications Systems Third Edition. Govind P. Agrawal Copyright 2002 John Wiley Sons Inc. ISBNs 0-471-21571-6 Hardback 0-471-22114-7 Electronic Chapter 4 Optical Receivers The role of an optical receiver is to convert the optical signal back into electrical form and recover the data transmitted through the lightwave system. Its main component is a photodetector that converts light into electricity through the photoelectric effect. The requirements for a photodetector are similar to those of an optical source. It should have high sensitivity fast response low noise low cost and high reliability. Its size should be compatible with the fiber-core size. These requirements are best met by photodetectors made of semiconductor materials. This chapter focuses on photodetectors and optical receivers 1 - 9 . We introduce in Section the basic concepts behind the photodetection process and discuss in Section several kinds of photodetectors commonly used for optical receivers. The components of an optical receiver are described in Section with emphasis on the role played by each component. Section deals with various noise sources that limit the signal-to-noise ratio in optical receivers. Sections and are devoted to receiver sensitivity and its degradation under nonideal conditions. The performance of optical receivers in actual transmission experiments is discussed in Section . Basic Concepts The fundamental mechanism behind the photodetection process is optical absorption. This section introduces basic concepts such as responsivity quantum efficiency and bandwidth that are common to all photodetectors and are needed later in this chapter. Detector Responsivity Consider the semiconductor slab shown schematically in Fig. . If the energy hv of incident photons exceeds the bandgap energy an electron-hole pair is generated each time a photon is absorbed by the semiconductor. Under the influence of an electric field set up by an
