Modeling of intensity fluctuations in the turbid underwater wireless optical communication links

The performance of the underwater wireless optical communication (UWOC) point-to-point link is strictly affected by the turbulent nature of the ocean. The underwater turbulence mainly arises due to the random variations in the refractive index of the propagating medium, which limits the transmission range of the UWOC links. We study experimentally the effect of salinity-induced turbulence on the propagating optical beam. Three different channel scenarios have been considered, namely, uniform salinity concentrations, salinity gradients, and the different sized air bubbles. In the uniform channel, the received optical power follows an exponential decay with the increase in the salinity concentration in the water. The different gradients and air bubbles create random variations in the refractive index of the water, which results in a random fluctuation in the received intensities. These intensity fluctuations are modeled using the Gaussian mixture model (GMM), which is the sum of the Gaussian functions. The feasibility of both the proposed models is verified by conducting a goodness of fit test in terms of R-2 and root means square error coefficients. The values of these coefficients indicate that the GMM acceptably matches the acquired experimental observations. Furthermore, the performance of the UWOC point-to-point link is also evaluated using the proposed model. The bit error rate of approximately 10 (- 6) that corresponds to a signal-to-noise ratio of 43 dB has been estimated for both uniform and nonuniform channels at an air flow rate of 24 L / min. Hence, the proposed model can efficiently describe the effect of salinity variations, gradient conditions, and air bubbles in the turbulent UWOC point-to-point links. (c) 2022 Society of Photo-Optical Instrumentation Engineers (SPIE)