Experimental Research on Underwater Visible LightTwo-way Voice Communication based on PIN

Aiming at the problems of limited communication distance and low transmission rate of underwater radio frequency communication system, Visible Light Communication (VLC) system provides a solution for underwater medium and long distance high-speed wireless communication. In this paper, the underwater short-range channel model is estimated by using the sample water quality test. A test method of attenuation coefficient of short-range optical medium is proposed, and an underwater VLC system is developed. The direct-current bias circuit is designed according to the volt ampere characteristics of Light Emitting Diode (LED), and its spectrum response is analyzed. The underwater full duplex audio experiment with blue 465 nm and white light source is carried out in a water tank. The experimental results show that when the rated optical power is 1 W, the receiving end adopts S6968 silicon Positive Intrinsic Negative (PIN) photodetector, and the system can carry out full duplex communication in the sample water (denoted attenuation coefficient c=0.2067 m-1). The communication distance between the two light sources is more than 5m. The speech communication performance of the experimental system is verified through the analysis of the power spectrum estimation of the receiving signal, the signal-to-noise ratio test and the visual demonstration of the loudspeaker. The experimental results provide a guidance for the development of underwater VLC multi-service transmission system.