Comprehensive experimental and statistical analysis of the effects of salinity gradient, temperature gradient, air bubbles on the performance of underwater wireless optical communication link

Salinity gradients (SGs), temperature gradients (TGs), and different-sized air bubbles affect the optical signal propagating in the UWOC link. These effects contribute to beam wandering, spot dancing, and intensity fluctuations in the received optical signal. In this paper, experimental analysis has been carried out to estimate the effect of SG, TG and air bubbles on the underwater optical signal. The beam wandering, mean and variance deviation, displacement of weighted centroid, the statistical distribution of received intensities and link outage probability have been estimated in this work. It has been found that the beam wandering effects follow a Gaussian mixture model (GMM). It is also observed that in the presence of air bubbles in the SG, the chances of link outage increase from 48% to 80% and it increases from 7% to 28% in the TG conditions. Furthermore, the experimental and theoretical modelled outage probabilities are in close agreement.

盐度梯度（Salinity gradients, SGs）、温度梯度（Temperature gradients, TGs）以及不同尺寸的气泡，均会对UWOC链路中传输的光信号产生干扰作用。这类干扰会导致接收光信号出现光束漂移、光斑抖动以及强度起伏等问题。本文通过开展实验分析，量化评估盐度梯度、温度梯度与气泡对水下光信号的影响。本研究针对光束漂移、均值与方差偏差、加权质心位移、接收光强统计分布以及链路中断概率等指标开展了量化测算。研究结果表明，光束漂移效应符合高斯混合模型（Gaussian mixture model, GMM）。同时研究发现，当盐度梯度环境中存在气泡时，链路中断概率从48%提升至80%；而在温度梯度环境中，链路中断概率则由7%升至28%。此外，实验测得的中断概率与理论建模得到的中断概率吻合度极高。