Information Capacity of Turbulent and Absorptive Underwater Wireless Link with Perfect Laguerre–Gaussian Beam and Pointing Errors

Abstract

The model of information capacity for underwater wireless optical communication (UWOC) links with pointing errors and the carrier of perfect Laguerre–Gaussian (PLG) beam in absorbed and weakly turbulent seawater is modeled. Using this model, the influence of channel parameters on the propagation of PLG beams is numerically analyzed. We show that the pointing error significantly reduces the performance of the optical transmission system. Large topological charge and radial orders are not conducive to high information capacity transmission. Additionally, the information capacity decreases with the increase in the spectral absorption coefficient of seawater. With higher transmission power, the transmission of an optical transmission system with high average capacity can be realized. The information capacity is affected by both signal wavelength and seawater absorption coefficient. That is, in the case of small seawater absorption and short message channel, the channel capacity loss of the link with long signal wavelength is smaller. In the case of long channels and strong seawater absorption, the influence of signal wavelength on the average capacity can be ignored. The information capacity of the communication link is the highest, which is composed of the carrier with the OAM topological charge, and the radial orders are both 1, and the wavelength is 410 nm.