Analysis of optical communications through the random air-water interface: feasibility for under-water communications

New results for investigating optical propagation through the random wavy air-water interface relevant to underwater optical communications are presented. A laser beam propagating through the air-water interface reaching a receiver below the water surface, as well as propagated through the water towards an airborne receiver, is significantly distorted due to the high geometric phase aberrations introduced by the random motion of the water surface waves. This causes a significant reduction in the received communications signal resulting in limiting the data transfer capability and the transmitting and receiving data rates. This research develops probabilistic models for optical propagation at the random air-water interface for both reflection and transmission cases under various wind speed conditions. Preliminary results from a laboratory water tank experiment provide information about histograms or the probability density functions of intensity fluctuations measured by a CCD camera for both reflection and transmission cases. Angular displacements of the centroid of the fluctuating laser beam generates the beam wander effects. Finally preliminary results for BER estimates for an on-off keying (OOK) for air-water interface only are presented for a communication system where random air-water interface is a part of communication channel.