Performance analysis of multihop FSO systems using APD receivers over log-normal channels

This paper studies the performance of multihop free-space optical (FSO) communication systems using the binary phase-shift keying modulation (BPSK) and avalanche photodiode (APD) receivers over atmospheric turbulence channels. We consider both serial and parallel relaying configurations with the decode-and-forward (DF) mode. The outage probability is analytically derived taking into account the log-normal turbulence channel model and receiver noise for both relaying configurations. In our analysis, the optimum of APD gain for achieving lowest outage probability with different relaying configurations and receiver parameters is discussed. The analytical results are verified by Monte-Carlo simulation and a good agreement between the analytical and simulation results is confirmed.