Demonstration of anti-diffracting optical pin-like beam enabled 5Gbit/s OFDM underwater wireless optical communication system

In the underwater wireless optical communication (UWOC) system, strong optical scattering caused by impurity particles in the water leads to the rapid divergence of the beam. This results in a significant decrease in the received light power when using a restricted-size aperture. The challenge is overcome by utilizing a new structured optical beam called a "pin-like beam". In this study, we built a 5Gbit/s UWOC system in tap water to compare the propagation performance of four beams: Gaussian, zero-order Bessel, pin-like, and pin-like vortex+2 beams. The experimental results showed that the pin-like and pin-like vortex+2 beams have an auto-focusing property, maintaining a narrow beam characteristic over a range after the auto-focus position. Additionally, the results indicated that the proposed pin-like and pin-like vortex+2 beams have lower power loss compared to the Gaussian and zero-order Bessel beams when using a size-limited receiver aperture.