Free space optical (FSO) communication systems are an attractive alternative for wireless communication links. A turbulent FSO channel can be modeled by a gamma-gamma probability density function (pdf. However, when two or more overlapping lasers that have the same central frequency but have random polarization and phase angles, the gamma-gamma pdf cannot represent the intensity In this paper we investigate via Monte Carlo Simulation the effect of both the beat noise and turbulence on the detected pdf when a FSO system uses a number of overlapping lasers. Results show that the beat noise is the dominant source of noise, while a turbulent channel A gamma pdf can give a good approximation of the intensity when the number of overlapping lasers is greater than sixteen, otherwise, the empirical pdf is provides a better estimate.
