Underwater Transmission Characteristics of Blue OAM Vortex Beams

Abstract To mitigate channel-induced degradation in underwater wireless optical communication (UWOC), this study combines theoretical and experimental analyses to characterize 488 nm blue OAM beam propagation across varying temperatures, salinities, and distances. Under short-range conditions, received power decreases monotonically with increasing temperature (10 ∼ 30°C) and salinity (10 ∼ 35 PPT), though overall attenuation remains modest. Notably, salinity fluctuations exerted a more pronounced impact (0.167%/PPT) than temperature (0.023%/°C). Transmission distance is a key factor driving exponential power loss and quality degradation, with an average relative loss of 11.1%/m due to cumulative water attenuation and reflective losses. Furthermore, transmission efficiency proved highly mode-dependent: lower-order modes (l = 1) exhibited superior robustness and stability over higher-order modes (l ≥ 3), owing to their reduced diffraction divergence and compact energy distribution. These findings provide critical theoretical and experimental guidance for modal selection and link design in UWOC systems.