Effect of moving microalgae on underwater wireless optical links.

Underwater wireless optical communications is a promising technique for addressing short-range data networks, as it provides cost, performance, and complexity improvements as compared with other alternatives, such as acoustic communications or radio frequency links. It is a part of the optical wireless communications research area, since for these applications, broad optical sources such as visible LED lamps can be used. Unless those links are designed for short distances (about 1 m, as in data-muling services on internet-of-things submerged systems), they are still severely affected by channel perturbations, such as scattering due to the presence of particles. This effect is particularly important when considering sensing applications for algae or aquaculture farming, which are becoming a crucial economic resource in many maritime areas. In this work, the effects of moving microalgae on underwater short-range optical links are studied so as to estimate a model for this scattering under dynamic conditions. The statistical parameters over experimentally measured received signal level and signal-to-noise ratio (SNR) are calculated, and the experimental setup is described. Results show that in clear water (no-algae scenario), the water-pump-induced movement effect over the mean and variance of the received optical power can be neglected, while when microalgae are present, the average optical power value decreases and the variance increases with all measured wavelengths. Finally, the SNR penalty due to the movement of microalgae is statistically evaluated.