A comprehensive performance analysis of PPM-based FSO systems with APD receiver in atmospheric turbulence

In this paper, a model of Gaussian pulse propagation over atmospheric turbulence channel is used to comprehensively analyze the performance of PPM-based free-space optical communication (FSO) systems with APD receiver. This model simultaneously takes into account all effects of atmospheric turbulence including intensity fluctuation and pulse broadening, which has not been considered in previous works. In addition, the impacts of APD shot noise, background noise, and thermal noise are included in our analysis. The numerical results show that, when M ≤ 128, the main factor that limits the system performance is intensity fluctuation. However, when M >; 128, optical pulse is so short that the effect of pulse broadening becomes dominant. Moreover, we found that APD gain of 60 is the optimum value that helps to achieve the lowest bit-error rate. Finally, based on channel capacity, we are able to determine the maximum transmission length of the system.