A Design and Implementation of Underwater Wireless Optical Communication System

With extremely high information rate, great data transmission capability, and strong anti-interference, underwater wireless optical communication (UWOC) becomes a promising short-range solution for various marine sensors and types of equipment. Related key technologies are discussed in this paper, and a laser diode (LD) and an avalanche photon diode (APD) are selected as light source and receiver. The 450 nm light beam will be generated, and modulated using orthogonal frequency division multiplex (OFDM) for its adaptive ability and resistance to multipath effect. Therefore, a Qualcomm QCA6410 chip with OFDM module is chosen as core processor. Furthermore, a constant current driver circuit, a TPS55340-based negative bias generator with temperature compensation, and a trans-impedance amplifier (TIA)-based post-stage signal processing unit are designed to steadily drive the LD, provide the high voltage leading to the avalanche effect of the APD and generate differential signals that can be received by the chip, respectively. Finally, a full-duplex UWOC system is implemented and tested in a one-meter-long water tank under several water conditions. Results show that a stable data link will be connected with water attenuation coefficient of less than $1.58\ m^{-1}$, and an average data rate of 6.6 Mbits/s ∼ 10 Mbits/s can be achieved.