Impact of different noise sources on the performance of PIN- and APD-based FSO receivers

P-i-N (PIN) diodes and avalanche photo-diodes (APD) are the most commonly used photo-detectors in terrestrial FSO systems. In this paper, we review the photo-detection process for the cases of PIN- and APD-based receivers and provide a comprehensive study of different noise sources that affect signal detection in an FSO system. We present a complete and precise model for the receiver noise by taking different receiver parts into account. In particular, we study the impact of thermal, shot, background, and transmitter noises on the receiver performance by considering practical and realistic case studies. We bring clearance on the impact of the interaction of signal and background noise due to non-linear characteristic of the photo-detector, and on the role of the trans-impedance load resistance. We discuss the dominant noise components for the cases of using a PIN or an APD, and compare their performances at the presence or not of background radiations.