ADAPTIVE OPTICAL TRANSMITTER AND RECEIVER FOR SPACE-COMMUNICATION THROUGH THIN CLOUDS

Optical space communication from satellite to ground or air to air con sists of clouds as part of communication channels. Propagation of opti cal pulses through clouds causes widening and deformation in the time domain and attenuation of the pulse radiant power. These effects decre ase the received signal and limit the information bandwidth of the com munication system. Having dealt with the other effects previously, her e we concentrate on pulse broadening in the time domain. We derive a m athematical model of an adaptive optical communication system with a m ultiscattering channel (atmospheric cloud). We use knowledge about the impulse response function of the cloud to adapt the communication par ameters to the transfer function of the cloud. The communication syste m includes a receiver and a transmitter. We adapted the transmitter to atmospheric conditions by changing the bit error rate. One can adapt the receiver to the atmospheric condition by changing the parameters o f the detector and the filter. An example for a practical communicatio n system between a low Earth orbit satellite and a ground station cove r by cloud is given. Comparison and analysis of an adaptive and semiad aptive system with cloud channels are presented. Our conclusion is tha t in some cases only by such adaptive methods is optical communication possible. (C) 1997 Optical Society of America.