Visibility statistics based unavailability events estimation of FSO link due to fog in four cities of Pakistan

Currently researchers are very interested in FSO (Free Space Optics) as compare to conventional fiber optic and RF transmission systems at last mile because FSO facilitates easy deployment, cost effective and high data rate with licensed free spectrum. Like other open air wireless systems local climate make performance inefficient due to interference of propagation impairments like rain, fog, mist, haze, snow etc. The effect of fog on narrowband (780 nm to 850nm & 1529 nm to 1600 nm) transmission of FSO system is high due to the comparable drop size of fog with operating wavelength of FSO link. This paper focused on the unavailability events estimation through Kim, Kruse, advection and convection fog attenuation models on the basis of available Visibility statistics of Karachi, Lahore, Islamabad and Sukkur.