Impact of Optical Crosstalk on OIRS-Assisted HAP-Based Multiuser FSO Systems over Turbulence Channels

Free-space optical communication (FSO) utilizes laser beams to transmit data through the atmosphere. However, FSO faces significant challenges, including the strict requirement for line-of-sight (LoS) communication and terrestrial obstacles, which limit its scalability to connect multiple users in diverse environments. To address these limitations and enable reliable multi-user connectivity, the integration of high-altitude platforms (HAP) and optical intelligent reflecting surfaces (OIRS) has emerged as a critical solution. To serve multiple users simultaneously, an OIRS is equipped at the HAP to dynamically control the reflected beam from a ground station to the terminals. This study analyzes the proposed FSO system performance through the outage probability. During the analysis, practically influencing factors such as optical crosstalk, i.e., interference between OIRS regions, and atmospheric turbulence, are considered. The numerical results show the feasibility of deploying OIRS on HAP to support multiuser FSO systems. In addition, properly designing the OIRS coverage could improve the overall performance of the multiuser FSO system.