BPSK intensity modulated free-space optical communications using aperture averaging

Atmospheric turbulence-induced intensity fluctuations severely impair Free-Space Optical (FSO) communication systems, affecting the quality of the propagated laser beam and lead to significant performance degradation. By using aperture averaging technique, we investigate the performance of the FSO system using a Subcarrier Intensity Modulation (SIM) based on a Binary Phase Shift Keying (BPSK) scheme under weak-to-strong atmospheric turbulence regimes. The performance is assessed in terms of both the Carrier-to-Signal Ratio (CNR) and the Bit-Error-Rate (BER) of the SIM-BPSK system by applying a modified model taking into consideration the aperture averaging. We show that there is a design tradeoff between the receiver lens aperture and the required CNR to achieve a given BER.