Performance Analysis of Underwater Optical Wireless Communication Using O-RIS and Fiber Optic Backhaul (Extended version)

This Letter presents a novel hybrid underwater wireless optical communication (UWOC) system that integrates underwater optical access points (UOAPs) with a passive optical network (PON)-based fiber-optic backhaul to provide a resilient backbone. A hard switching mechanism is employed between direct and optical reconfigurable intelligent surface (O-RIS)-assisted links to ensure reliable connectivity. Unlike previous studies, the proposed system is evaluated under both active and multiple passive O-RIS configurations. To enhance reliability, the Selection Combining (SC) and Maximal Ratio Combining (MRC) schemes are applied. Analytical and simulation results demonstrate that optimal O-RIS placement significantly enhances system performance. However, in the linear regime, placing it too close to the receiver causes degradation due to increased path loss and beam jitter in an identical water type. Moreover, increasing the number of O-RIS elements within practical limits further improves overall system performance and enhances adaptability to variations in the underwater channel.