Performance analysis of all-optical amplify and forward relaying over log-normal FSO channels

In this paper, we propose a comprehensive analysis of all-optical relaying free space optical (FSO) systems in the presence of all main noise sources, including background, thermal, and amplified spontaneous emission noise, by considering the effect of the optical degree-of-freedom. Using full channel-state information (CSI) and semi-blind CSI relaying, we derive closed-form expressions for the ergodic capacity, outage capacity, and outage probability of the considered dual-hop FSO system. Numerical and analytical simulation results are provided to verify the accuracy of the proposed mathematical analysis. To simplify analytical expressions of full CSI relaying, we also propose and analyze the validity of different commonly used approximations in the context of dual-hop FSO communications.