Investigations on spectrum sliced-wavelength-division multiplexed visible light communication transmission for underwater links under varying turbulent conditions

摘要

Underwater visible light communication (UVLC) transmission systems have garnered significant attraction in comparison to their radio-frequency and acoustic counterparts due to their inherit merit of significantly higher channel bandwidth. We propose the modelling of a novel spectrum sliced-wavelength-division multiplexed UVLC transmission system. In the proposed work, a single 532 nm blue-green laser diode is spectrum sliced into 4 distinct wavelengths by employing a 1 x 4 de-multiplexer, where each wavelength transmits independent 10 Gbit/s binary data through the underwater channel. At the receiver terminal, independent signals are retrieved and the performance is investigated using bit-error rate, eye diagrams and quality factor (Q Factor) with increasing underwater transmission range. Furthermore, the system's performance is compared for non-return-to-zero (NRZ), returnto-zero (RZ), and alternative mark inverted modulation techniques under water turbulent conditions including coastal ocean, pure sea, and clear ocean, and beam divergence. The reported results demonstrate superior NRZ modulation scheme performance and a reliable 40 Gbit/s transmission along 260m-60 m depending on the type of water turbulence.