Underwater wireless optical communication system using a 16-QAM modulated 450-nm laser diode based on an FPGA

An underwater wireless optical communication (UWOC) system with a 450-nm laser diode and a 150-MHz PIN photodiode is presented. The 16-ary quadrature amplitude modulation scheme is employed and realized on a field-programmable gate array (FPGA) to efficiently provide a high data rate. Experimental results show that this system can achieve data rates up to 50 Mbps over a distance of 3 m underwater with a bit error rate (BER) of 7.11×10^-4 in artificial seawater at 35‰ salinity, where the attenuation coefficient is 0.481. This BER is below the forward error correction target of 3.8×10^-3. Thus, this system can provide reliable high-speed communications over short to moderate distance point-to-point UWOC links.