Underwater optical wireless communication using a green laser

Abstract

Visible light communication (VLC) emerging as an essential technology in the 6G era has expanded its application from indoor to outdoor scenarios. Underwater optical wireless communication (UOWC) technology is presented aiming to provide high-speed and safe communication service for complex underwater scenarios. The blue-green band exists as a transmission window in seawater with less transmission loss than other visible light counterparts. In this paper, a self-designed full-duplex UOWC transceiver is demonstrated. A green laser and an avalanche photodiode (APD) are used as core devices of the transmitter and receiver, respectively. We use a field programmable gate array (FPGA) as the main processing unit where an on-off-key (OOK) modem and reed-solomon (RS) coder are adopted which can correct up to 8-bit errors at a correction efficiency of 94%. A bias-tee module is used as the emitting driver of the modulated signals for the green laser diode (LD) and a receiving circuit is self-designed realizing photoelectric conversion and signal processing, in which the transceiver could simultaneously emit and receive light. We conducted an experiment using a water flume to simulate underwater communication channels and realize full-duplex communication. The transmission rate of the transceiver is 5 Mbps. The photoelectric properties of the LD are characterized in this paper. Eye patterns and flowing signals are analyzed for the communication performance of the transceiver. This work provides a feasible method for advanced UOWC technology.