Performance Evaluation of Underwater Wireless Optical Communications Links in the Presence of Different Air Bubble Populations

TLDR

The study experimentally evaluates underwater wireless optical communication links under varying air bubble conditions. Bubbles of varying size and density were produced by an air pipe and a variable‑flow submersible pump that fragments large bubbles into smaller ones. Bubbles markedly degrade UWOC performance, with large bubbles causing complete beam blockage and deep fades, while smaller bubbles reduce fade severity, and beam expansion can alleviate the resulting signal loss.

Abstract

We experimentally evaluate the performance of underwater wireless optical communication (UWOC) links in the presence of different air bubbles. Air bubbles of different sizes and densities are generated by using an air pipe in conjunction with a submersible water pump of variable flow rate that helps break up large bubbles into smaller bubbles. Received signal intensity measurements show that bubbles significantly degrade the performance of UWOC links. Large bubbles completely obstruct the optical beam and cause a deep fade. However, as the bubble size decreases, the level of deep fade also decreases because the optical beam is less susceptible to complete obstruction, and more light reaches the detector. We also show that beam expansion could help mitigate the performance degradation due to the deep fade caused by air bubbles scatters in the channel.