FREE-SPACE OPTICAL COMMUNICATION - DETECTOR ARRAY APERTURE FOR OPTICAL COMMUNICATION THROUGH THIN CLOUDS

Optical communication must contain clouds as parts of communication ch annels. Propagation of optical pulses through clouds causes widening i n the spatial domain and attenuation of the pulse radiant power. These effects decrease the received signal and increase bit error rate (BER ). One way to improve the BER of the communication system is by using adaptive methods to obtain more signal relative to noise power. Based on mathematical models of spatial widening of optical radiation derive d by Monte Carte simulation, a mathematical model for optimum performa nce of digital optical communication through clouds is developed. The purpose of the optimum adaptive communication system suggested here is to improve the BER by optimizing according to meterological condition s the spatial distribution of the detected radiation beam using a dete ctor array where the external amplification of each detector is adapta ble. Comparison and analysis of three models of communication systems in fog cloud channels are presented: (1) the optimum adaptive detector array aperture, (2) an ordinary single detector aperture of the same size, and (3) a small detector aperture. Improvement of more than four orders of magnitude in BER under certain conditions is possible with the new adaptive system model.