Free-Space Optical Communication With Optical Intelligent Reflecting Surfaces Under Phase Errors

Free-space optical (FSO) communication systems enhanced with optical intelligent reflecting surfaces (OIRS) offer promising solutions to overcome line-of-sight limitations and mitigate atmospheric turbulence effects. This paper presents a comprehensive analysis of OIRS-assisted FSO systems with phase errors utilizing both heterodyne and intensity modulation with direct detection (IM/DD) methods, which provides a more tractable alternative to existing methods. We first derive exact closed-form formulas for the mean and variance of the squared sum of products of independent, identically distributed Gamma-Gamma random variables, incorporating both pointing errors and IRS phase errors. Based on these results, we approximate the square envelope of the OIRS-assisted FSO channel with a Gamma distribution, with shape and scale terms determined from the derived mean and variance. This approximation allows us to obtain closed-form expressions for key performance metrics, including the average bit-error rate for different modulations, the outage probability, and the ergodic capacity, expressed using the Meijer’s G function. Our approach demonstrates excellent agreement with Monte Carlo simulations while offering superior computational efficiency compared to methods based on multivariate Fox’s H functions. Furthermore, we conduct asymptotic analysis at high signal-to-noise ratios and investigate the system’s diversity order for both heterodyne and IM/DD techniques.