A Survey: RTE Solutions for Underwater Optical Communications

The Radiative Transfer Equation (RTE) is essential for solving the spatial distribution of light energy. It plays a crucial role in the link budget analysis of Underwater Wireless Optical Communication (UWOC). However, due to its complex integro-differential form, obtaining an exact solution is extremely challenging. This paper provides a systematic overview and comparison of key RTE solution strategies in case of UWOC scenario—including the Monte Carlo Method (MCM), Beer–Lambert Method (BLM), Beam Spread Function (BSF), Finite Element Method (FEM), and others—and analyzes how each approach balances accuracy, computational efficiency, and ease of implementation. Results show that MCM, though computationally intensive, to best match the three-dimensional spatial configuration of practical UWOC systems. BLM, while simplest, loses accuracy in turbid conditions. BSF partially corrects for scattering but yields only modest gains over BLM, and FEM struggles at longer ranges due to discretization. These findings help guide method selection for reliable estimation UWOC system power budget.