Abstract

In this paper, we analyze the spatial location of the eavesdropper on the secrecy performance of free-space optical communication systems over Fischer--Snedecor F-distribution fading channel. As a key feature, we investigate the impact of the eavesdropper's location within the range of the beam divergence angle, which is more in line with practical engineering applications. The possible position of the eavesdropper is comprehensively assumed with horizontal and vertical components within the beam divergence angle. To this end, the lower-band secrecy outage probability, asymptotic solutions of SOP at high signal-to-noise-ratio, and the strictly positive secrecy capacity are obtained in closed-form, which are corroborated by exact Monte Carlo simulations respectively.