ABSTRACT
This chapter describes fundamental aspects of the optoelectronic detection process. It discusses important properties of state-of-the-art receiver hardware, that of pin photodiodes and avalanche photodiode particularly, optical filters, optical amplifiers, and local lasers. The chapter explores the performance of various types of digital optical receivers and explains their sensitivities. It explores the impact of background radiation for various types of receivers. The chapter analyses the critical aspects and recalls the choices which have to be made when designing a receiver for a free-space, high-data-rate link. Background radiation originating from the Sun, Moon, planets, or from the sunlit Earth may be picked up by the receive antenna and directed to the photodetector, thus presenting optical noise to the receiver. Although electronics noise usually dominates shot noise, it could be engineered to insignificance by cooling the receiver. The intriguing performance characteristics of erbium-doped fiber amplifiers have made optically preamplified receivers an attractive detection technique.
