Underwater optical communications systems part 1: variability of water optical parameters

In this paper, we examine the fundamental physics and natural variability of underwater (u/w) optical attenuation. Using data collected recently in the Yellow Sea, Arabian Gulf, and East China Sea, we describe the persistent features of the near-surface and near-seafloor optical conditions. Depth profiles are shown for optical parameters relevant to u/w communications studies: the diffuse attenuation coefficient (K) and the beam attenuation coefficient (c). Profiles of K and c demonstrate how these coefficients can vary with depth. Sediment-laden nepheloid layers occur at the bottom of many littoral waters; the largest effect is usually in the shallowest water profiles. There can be a significant difference in the communications range at the top and bottom of the water column. This paper shows that satellite data can only be used to estimate optical attenuation coefficients in the top layers of the water column; they does describe the water clarity in littoral waters of any significant depth because this type of remote sensing misses the subsurface variability. Therefore, in-situ profiles are needed to accurately describe the vertical variability in optical clarity that is needed to evaluate u/w optical communication performance