Design and simulation of SPAD-based UWOC for turbid waters

Single-photon avalanche diodes (SPADs), featuring ultra-high sensitivity and fast response speed, are widely used in underwater wireless optical communications (UWOC). Since the attenuation coefficient of red light is smaller than that of blue-green light in highly turbid waters, therefore, a red-enhanced SPAD based on 250 nm BCD process was specially designed to improve its photon detection efficiency (PDE) in red light band, and then a SPAD-based UWOC simulation system for turbid waters channel was developed in this work. The UWOC simulation results with custom-designed SPAD shown that the transmission distance is up to 75 m for a data rate of 1 Mbps at BER of 3.8×10-3, and the effective communication distance was improved by at least 15% compared to the UWOC system with blue-green SPADs. This indicated that our-designed SPAD can effectively improve the communication performance of UWOC in turbid waters. Besides, the impact of SPAD’s working condition such as excess bias voltage, operating temperature and dead time, on BER was analyzed as well.