Methodology for realization of given BER in FSO systems under effect of internal and external noises

A methodology to compensate for the influence of external noises on the set value of BER, respectively the SNR, at the output of the optical receiver of the FSO systems has been developed. This compensation is achieved by increasing the power in the input of the receiver´s photodetector together with a corresponding expansion of the optical beam of the transmitter. An important point in the methodology is finding the optimal angle of divergence of the laser beam. At this angle, the required transmitter´s power obtains a minimum value.