Study on transmission characteristics of OAM beam in underwater channel

Underwater wireless optical communication (UWOC) based on the orbital angular momentum (OAM) beam has great potential to provide a higher data rate and lower communication latency. When the OAM beam propagates underwater, due to the absorption and scattering (AS) effect, the incident light would be attenuated and diffused, causing the crosstalk between OAM modes. In this paper, the electric field Monte Carlo (EMC) method is used to simulate the AS effect by the optical transmission matrix (TM) model. The intensity and the spiral phase spectrum of the received beam at different propagation distances are studied under the coastal ocean water channel. Furthermore, the detection probability is analyzed after propagating through the coastal ocean water and turbid harbor water channels. The simulation results show that the detection probability of OAM beam propagating in an AS channel decreases linearly with the increase of propagation distance. In coastal ocean water (attenuation coefficient 0.398m⁻¹), the detection probability decreases to 0.5 at around 10m. In turbid harbor waters (attenuation coefficient of 2.17m⁻¹) the detection probability decays to 0.5 at around 2m. These results will be beneficial to the design of UWOC-OAM systems.