Optical Sources and Detectors

The light waves, as electromagnetic continuous waves, can be regarded as a probability function whose intensity at any point in space defines the probability of finding a photon there. According to this wave–particle dualism, the emission and/or the absorption spectrum of any material can be used for its identification and to determine the quantity present. The most commonly used light sources in optical communication are the light‐emitting diode and the laser diode. This chapter provides a discussion on different kinds of optical receivers and their operational characteristics that are based on similar basic physical parameters of both kinds of diodes. The most common photodetector for optical communications (fiber and wireless) is the semiconductor junction photodiode, which converts optical power to an electric current. There is a frequency “responsivity” spectrum for each type of photodiode, which, consequently, must be matched to the spectrum of the light which is to be detected.