Fading Analysis of Direct Detection Free Space Optical Systems under Different Atmosphere Conditions

Free space optical communication systems have been used in many communication applications and especially the communication through the free medium such as the atmosphere. However, they are still having some performance limitation due to the atmosphere turbulence. In this paper, we will test an important factor that affects the performance of any free space optical communication system, which is fading in the received signal. The signal fading is tested under week to moderate turbulent atmosphere. We will use the conventional Kolmogorov power spectrum model to evaluate a free space optical system when the probability distribution function is characterized by log-normal probability distribution function (PDF). The probability of fade and fading time will be discussed. Also, the acceptable fading threshold is tested for optical system under the given conditions.