Optical Communications Between Underwater and Above Surface (Satellite) Terminals

A multiple scattering model is used and extended to characterize the channel between underwater and airborne (satellite) terminals at optical frequencies. The effects of the air/sea interface are also included with approximate solutions accurate for elevation angles above 45°. The results are presented in terms of a radiance function which is related to the transform of the spatial covariance function (mutual coherence function). The primary losses are shown to be a result of the water absorption coeffecient and not the extinction coefficient. The scattering losses can be isolated from the absorption losses and for certain cases, where the receiver is imbedded in the scattering medium, can be completely recovered. New components may be required to achieve this performance. The effects of ocean roughness are shown to have a minimal effect upon the subsurface reception while causing possible beam steering of subsurface transmission. Although substantial losses are experienced, duplex operation can be achieved at modest data rates.