Experimental Saturation Characteristics of PMT from DC to 1GHz and Adaptive Compensation Algorithm for High-Speed UOWC

A photomultiplier tube (PMT) may get saturated if the incident optical power approaches the saturation threshold for an underwater optical wireless communication (UOWC) system. This paper introduces a representation method of high-speed PMT saturation level based on the measured amplitude of direct current associated with frequency characteristics of the PMT output from DC to 1 GHz. Then, an adaptive optical saturation compensation algorithm based on electronic-controlled variable optical attenuator (VOA) is proposed to realize a reliable high-speed UOWC system. Experimental results demonstrate that a higher tolerance for large dynamic signal and background radiation for a 2 Gbps UOWC system can be achieved with BER below the forward error correction (FEC) limit.