Capacity analysis of free space optical links for a partially coherent Gaussian beam over a turbulent channel with pointing errors

In this paper, we investigate the joint effects of beam width and the spatial coherence length in a partially coherent free-space optical (FSO) link from the information theory perspective, taking into account the combined influence of atmospheric turbulence and pointing errors. In addition, the effects of aperture-averaging on the average capacity of FSO links employing partially coherent beams (PCBs) are examined. Results show that PCBs are desirable in the weak-to-moderate turbulence regime, whereas highly coherent laser sources are preferred under strong fluctuations conditions; and there exist optimality in the optical beam parameters for different atmospheric channel conditions. Near-optimal average capacity is best achieved through the introduction of a larger receiver aperture and the joint beam width and spatial coherence length optimization technique, which effectively mitigates the effects of scintillation and pointing errors.