Performance evaluation of a Free Space Optical (FSO) communication system impaired by atmospheric effects

Free Space Optical (FSO) links are very much promising for future terrestrial optical wireless applications due to high bandwidth and easy deployment compared to fiber optic links. However the FSO links are severely degraded by the presence of smoke, fog, snow, cloud etc. which attenuates the optical signal and causes dispersion of the optical pulses. In this paper an analytical approach is presented to evaluate the bit error rate (BER) performance of a FSO link in the presence of fog. Analysis is carried out to find the received optical power with field of view (FOV) of the transmitter to receiver as a parameter and other system parameters like transmitter power, wavelength, density of air etc. at a given bit rate considering on-off keying (OOK) modulation and direct detection receiver. The results are evaluated numerically in terms of SNR, BER and power penalty due to fog. Optimum FOV angle is determined corresponding to minimum BER at a given wavelength. It is noticed that FSO system suffer significant power penalty due to fog which is dependent on wavelength of optical carrier.