Large-coverage underwater visible light communication system based on blue LED employing equal gain combining with integrated PIN array reception.

In this paper, we proposed a large-coverage underwater visible light communication (VLC) system utilizing quadrature amplitude modulation-discrete multitone (QAM-DMT) and integrated 2×2 positive-intrinsic-negative (PIN) array reception to achieve equal-gain combining (EGC) receiving. The transmitter consists of a lens group and blue-emitting silicon substrate light-emitting diode peak emission, the wavelength of which is 458 nm. After 1.2 m underwater transmission, a data rate of over 1 Gbit/s is successfully achieved with a spot of 25 cm in diameter and 11 cm alignment tolerances. A data rate of 1.8 Gbit/s is also achieved when using parallel light reception. Both are the highest data rates to our knowledge so far in a large-coverage underwater VLC system, which shows the benefit and feasibility of using an integrated PIN array with QAM-DMT modulation and EGC.