Underwater optical wireless communications:Depth dependent variations in attenuation

Abstract

Depth variations in the attenuation coefficient for light in the ocean were calculated using a one-parameter model based on the chlorophyll-a concentration Cc and experimentally-determined Gaussian chlorophylldepth profiles. The depth profiles were related to surface chlorophyll levels for the range 0-4 mg/m2, representing clear, open ocean. The depth where Cc became negligible was calculated to be shallower for places of high surface chlorophyll; 111.5 m for surface chlorophyll 0.8 < Cc < 2.2 mg/m3 compared with 415.5 m for surface Cc < 0.04 mg/m3. Below this depth is the absolute minimum attenuation for underwater ocean communication links, calculated to be 0.0092 m-1 at a wavelength of 430 nm. By combining this with satellite surface-chlorophyll data, it is possible to quantify the attenuation between any two locations in the ocean, with applications for low-noise or secure underwater communications and vertical links from the ocean surface. © 2013 Optical Society of America.