Two-way 5G NR FSO-HCF-UWOC converged systems with R/G/B 3-wavelength and SLM-based beam-tracking scheme

A two-way fifth-generation (5G) new radio (NR) free-space optical (FSO)-hollow-core fibre (HCF)-underwater wireless optical communication (UWOC) converged systems with a red/green/blue (R/G/B) 3-wavelengths and spatial light modulator (SLM)-based beam-tracking scheme is practically built. It is the first to practically build a two-way FSO-HCF-UWOC converged system with high-speed and long-distance optical wireless-wired-underwater wireless communication characteristics. It shows a 5G NR FSO-HCF-UWOC convergence from drone or buildings to undersea, using R/G/B 3-wavelengths and an SLM as a demonstration. The R/G/B 3-wavelengths are used to enhance the downstream and upstream aggregate transmission rates. An SLM with electrical comparator is used to adjust the laser beam and mitigate laser beam misalignment caused by drone movement or ocean flow. Over a hybrid of 1-km FSO, 10-m HCF, and 10.44-m ocean water-air-ocean water medium, downstream/upstream 5G-millimeter-wave (MMW) 9.1-Gb/s/24-GHz signals are transmitted with satisfactorily low bit error rates and error vector magnitudes, as well as distinct constellations. This demonstrated that the 5G NR FSO-HCF-UWOC converged system exhibits promising potential as it advances the scenario implemented by the 5G-MMW signals over FSO, HCF, and UWOC convergence, paving the way for high-speed and long-distance communications across diverse media.