Multi-Degree-of-Freedom for Underwater Optical Wireless Communication with Improved Transmission Performance

Underwater optical wireless communication (UOWC) has great potential to provide high-speed and intensive communications over short ranges underwater. However, the mobility of UOWC system is limited by strict alignment requirements between transceivers. In this paper, a multi-degree-of-freedom (MDOF) with high flexibility improved transmission performance proposed experimentally demonstrated based on off-the-shelf light-emitting diode (LED) source. A hardware pre-equalization circuit employed at transmitter extend modulation bandwidth from 5.03 MHz 50 MHz. At receiving end, Fresnel lens array constructed achieve efficient convergence multiple incident signals different directions. To improve underwater signal quality, we designed an additional digital recovery module after trans-impedance amplifier. Finally, experimental established 460 nm blue LED. The reliability verified measurement eye diagram bit error rate recovered end. results show that three directions maximum data 100 Mbps are reliably transmitted 1.2-m-long water tank using non-return-to-zero on-off-keying format.