Modulation Analysis for Long Distance Underwater VLC Systems under Dead Time Limit

Underwater visible light communication (UVLC) has a very wide application prospect in ocean exploration. The single photon avalanche diode (SPAD) can expand system communication distance. In this paper, we study the SPAD based UVLC systems performance under dead time limited. To analyze the BER performance, we first get the model of the practical SPAD based UVLC system under the dead time limit. Then, we set up a long-distance VLC model based on the double exponentials decay. Furthermore, the maximum likelihood detection methods of different modulation schemes for the system are proposed. The simulation results show that the longest communication distance in pure sea water is 360 meters.