Cascaded FSO Systems With Optical Reflecting Surfaces

Recently, reconfigurable intelligent surfaces (RISs) have emerged as a highly promising technology within the realm of wireless communication systems, as they offer the potential to minimize obstructions, enhance reliability, and establish alternative paths for signal propagation. This article presents the performance of a free space optics (FSOs) system empowered by multiple optical reflecting surfaces (ORSs) over a Gamma-Gamma turbulence-induced fading channel with pointing errors by considering imperfections in channel state information (CSI). The expressions for probability density function (PDF) of the end-to-end FSO channel considering both perfect and imperfect CSI cases are derived. Further, the unified PDF and cumulative distribution function (CDF) of instantaneous signal-to-noise ratio (SNR) are determined under two detection schemes, i.e., intensity modulation/ direct detection and heterodyne detection for both perfect and imperfect CSI cases. Utilizing the derived CDFs, the closed-form expressions for outage probability and average symbol error rate (ASER) of the proposed multiple ORSs system are obtained along with performing asymptotic analysis. Finally, the numerical results indicate that the performance of ORS-assisted FSO systems is significantly degraded by severe turbulence, pointing errors, and imperfect CSI. However, the inclusion of ORSs and increasing their number improves the performance of ORS-assisted FSO systems in the presence of turbulence, pointing errors, and imperfect CSI, compared to FSO systems without ORSs.