Abstract
In this paper, we experimentally demonstrate for the first time a bidirectional underwater wireless optical communication system that is capable of transmitting an ultrahigh definition real-time video using a downlink channel while simultaneously receiving the feedback messages on the uplink channel. The links extend up to 4.5 m using QPSK, 16-QAM, and 64-QAM modulations. The system is built using software defined platforms connected to TO-9 packaged pigtailed 520 nm directly modulated green laser diode (LD) with 1.2 GHz bandwidth as the optical transmitter for video streaming on the downlink, and an avalanche photodiode (APD) module as the downlink receiver. The uplink channel is connected to another pigtailed 450 nm directly modulated blue LD with 1.2 GHz bandwidth as the optical uplink transmitter for the feedback channel, and to a second APD as the uplink receiver. We perform laboratory experiments on different water types. The measured throughput is 15 Mb/s for QPSK, and 30 Mb/s for both 16 QAM and 64 QAM. We evaluate the quality of the received live video streams using peak signal-to-noise ratio and achieve values up to 16 dB for 64 QAM when streaming UHD video in harbor II water and 22 dB in clear ocean.