Series-connected solar array for high-speed underwater wireless optical links

Solar panels are being increasingly used as detectors in underwater wireless optical communication (UWOC) systems, as the large detection area can significantly simplify the link alignment. However, the greatest problem in such a scheme is the limited bandwidth of the solar panel, which was originally optimized for energy harvesting rather than communication. In this Letter, we propose series-connected solar arrays for high-speed underwater detection, by taking a deep dive into the fundamentals of the solar array. As the size of the solar array increases from lx1 to 3x3, the -20-dB bandwidth increases from 4.7 MHz to 24.2 MHz. To further improve the frequency response, a reverse bias is applied on the array. With a reverse bias voltage of 90 V, the -20-dB bandwidth of the proposed 3x3 solar array is extended to 63.4 MHz. To the best of our knowledge, it is the highest bandwidth achieved among the reported solar panel-based optical communication systems with a large detection area. Using the proposed series-connected solar array, a data rate of 150 Mbps is achieved over a 35-m underwater channel with a frequency domain equalizer. The proposed system shows that off-the-shelf solar cells have great potential in high data rate UWOC systems. (C) 2022 Optica Publishing Group