Energy-Aware Underwater Optical System With Combined Solar Cell and SPAD Receiver

This letter designs a simultaneous lightwave and power transfer (SLIPT) system in the underwater environment using the power splitting technique. The data is sent by a laser diode and received by a multi-element receiver composed of a Single Photon Avalanche Diode (SPAD) and a solar cell that decodes the transmitted symbols and harvests electrical energy from the optical signal, respectively. In this context, we propose an energy-aware SLIPT system that optimizes the power split between the receivers and the SPAD detecting threshold to maximize the harvested energy while considering minimum link quality for the communication service. Although the optimization problem is not convex, we derive its feasibility conditions in terms of the system’s parameters and propose an optimal resource allocation algorithm. Finally, we introduce some numerical results to investigate the effect of SPAD’s dead time and other parameters on the system’s performance.