Free-space optical communication in the presence of atmospheric angular spread

In this paper, different optical detection schemes are investigated in the presence of turbulence-induced effects. Both log-amplitude fluctuations and angle-of-arrival (AOA) fluctuations introduced by atmospheric turbulence are taken into account in channel modelling. The impact of the angular spread can be thus determined based on the performance of the FSO receivers. For direct detection, we find the optimal receiver field-of-view (FOV) to improve the performance. We further show the benefit of coherent detection over direct detection in the presence of angular spread. Moreover, spatial diversity receivers which are able to significantly improve the performance of atmospheric optical systems are discussed in detail.