Experimental study of underwater wireless optical channel model

The propagation of a laser beam in an underwater environment gives rise to attenuation caused by absorption and scattering as well as fading caused by turbulence. These effects lead to a decrease in light power and fluctuations in light intensity. To account for variations in water velocity, flow direction, and distance in communication links, field measurements were conducted in rivers and ocean nearshore waters. Based on these measurements, a model for an underwater wireless optical channel was developed. Our study involves the measurement and analysis of light intensity fluctuation, loss of received light power, and the structure constant in various underwater regions. Additionally, the investigation examines the variation of the bit-error rate in relation to different signal-to-noise ratios. The results suggest that the river displays attributes of low turbulence, whereas the ocean's nearshore waters exhibit a moderate level of turbulence under the specified circumstances. As the velocity of the water increases, the scintillation index of the received optical signal also increases, indicating a higher degree of signal instability. When transmitting horizontally, the scintillation index of the received optical signal remains unaffected by the direction of water flow. Furthermore, as the distance between the transmitter and receiver increases, the scintillation index of the received optical signal intensifies, indicating a greater level of signal instability. The presence of the external interference factors can increase turbulence intensity. Within a depth range of 60 cm underwater, the turbulence intensity at different depths remains basically unchanged.