Investigations on the performance of IRS-assisted underwater wireless optical communication

Underwater wireless optical communication (UWOC) has emerged as a key technology to overcome the bottleneck of acoustic and radio frequency systems, offering high data rates and low latency. However, the severe absorption, scattering, turbulence, and water turbidity restrict the achievable communication range. To address this challenge, this work investigates the role of Intelligent Reflecting Surfaces (IRS) in extending UWOC coverage under diverse channel conditions. Closed-form expressions for maximum achievable link distance are derived for conventional relaying schemes, namely detect-and-forward (DF) and amplify-and-forward (AF), and are further extended to passive and active IRS-assisted configurations under both coherent and incoherent combining for UWOC. Analytical modeling and simulations are conducted for different water types, including pure sea, clear ocean, coastal, and harbor waters, to evaluate performance under varying extinction coefficients. Results demonstrate that while direct UWOC links are limited to a few tens of meters, IRS-assisted systems, particularly with coherent combining and active surfaces, enable significant range extensions. Comparative analysis confirms that IRS schemes achieve superior performance as compared to AF/DF relays, with DF relaying still dominating under stringent reliability requirements. The findings establish IRS as a promising enabler for robust, long-distance UWOC links in next-generation marine networks.