Optical Receivers

This chapter provides an overview of the various optical detector mechanisms and devices. Photodetectors typically fall into two classes: thermal and photon detectors. In addition, the latter can be further categorized in terms of four specific photon conversion mechanisms. They are photoemissive detectors, photoconductive detectors, photovoltaic detectors, and photoelectromagnetic detectors. The chapter focuses on the first three and imaging arrays and then looks at the possible noise sources in an optical receiver that influence the quality of signal reception. When these detector and noise mechanisms are combined with the received signal, one can obtain the arguably key parameter in detection theory, the electrical signal‐to‐noise ratio (SNR). The construction of this particular metric connects it with radio frequency (RF) engineering, so the synergism between the two areas can be easily exploited. The chapter also discusses SNR and its various definitions in optics, and explains other performance measures such as minimum detectable power and receiver sensitivity.