Effect of aperture averaging on bit error rate for DPSK modulated UWOC system over strong oceanic turbulence

Underwater wireless optical communication (UWOC) systems receive growing attention as an alternative technology to meet the high-speed and large-data requirement in various underwater applications due to their higher bandwidth, lower attention, lower time latency, lower power loss, better security and higher communication rate compared to acoustic communication as well as underwater radio frequency communication. Despite all these advantages, expect absorption and scattering effects, the turbulence effect under water, will also cause loss and fading on the received optical signal, and limit the viable communication range of UWOC systems. In moderate to strong oceanic turbulence, a differential phase-shift-keying (DPSK) modulated underwater wireless optical communication (UWOC) system with an aperture receiver is presented. The analytical expressions for bit error rate (BER) of UWOC system over moderate to strong oceanic turbulence are derived based on Gamma-Gamma channel model by the help of the Whittaker function. The variations of BER are investigated versus modulation methods, beam types, aperture diameters as well as four oceanic turbulence parameters, i.e., the rate of dissipation of kinetic energy per unit mass of fluid, the rate of dissipation of mean-squared temperature, the ratio of temperature to salinity contributions to the refractive index spectrum and the kinetic viscosity. The simulated results show that the performance improves when the UWOC system adopting spherical wave with DPSK modulation and averaging receive at a lower value of the rate of dissipation of mean-squared temperature, the ratio of temperature to salinity contributions to the refractive index spectrum, the propagation distance, a higher value of the kinetic viscosity or a lower and higher rate of dissipation of kinetic energy per unit mass of fluid.