Evaluation of atmospheric coherent length of free-space optical links by using phase fluctuation

Abstract

Atmospheric coherence length is one of the most crucial parameters for free-space optical (FSO) links, which can reflect the level of phase and amplitude fluctuations caused by the atmospheric turbulence. In this paper, we study the evaluation of the atmospheric coherence length of the FSO links. The analytical expression of atmospheric coherence length is rendered based on the phase fluctuation resulting from atmospheric turbulence by using the most realistic Bump model. The proposed method is validated theoretically with the Monte Carlo phase screen. Also, the experimental setup with respect to FSO links is established with the spatial light modulator to validate the method experimentally, wherein the fluctuated phase is collected by Shack-Hartmann sensor. The results show that the evaluation of atmospheric coherence length by the analytical expression is consistent with the theoretical prediction as well as the experimental measurement. Thus, the proposed method enables the accurate evaluation of atmospheric coherence length under various turbulence conditions, which can assist the performance analysis as well as design of free-space optical communication systems.