Scintillation index of an optical wave propagating through moderate-to-strong oceanic turbulence

In this paper, based on the extended Rytov theory that combines modified large-scale and small-scale amplitude spatial-frequency filters, we theoretically derive the scintillation index (SI) of the plane and spherical waves by means of the approximate oceanic refractive-index spectrum with the variable eddy diffusivity ratio propagating through moderate-to-strong oceanic turbulence. The mean bit-error rate (BER) of the underwater optical wireless communication systems is analyzed by use of the predicted SI and the gamma-gamma distribution model. Numerical results show that the obtained SI models are in good agreement with the results in weak-fluctuation regions. Also, we find that in weak turbulence, the mean BER drops sharply with the increase in mean signal-to-noise ratio, while in moderate-to-strong turbulence, the situation is opposite. We also note that the mean BER differs between the cases of unity and the variable eddy diffusivity ratio.