  Free space optics (FSO) is a promising solution for the need to very high
data rate point-to point communication. FSO communication technology became
popular due to its large bandwidth potential, unlicensed spectrum, excellent
security and quick and inexpensive setup. Unfortunately, atmospheric
turbulence-induced fading is one of the main impairments affecting FSO
communications. To design a high performance communication link for the
atmospheric FSO channel, it is of great importance to characterize the channel
with proper model. In this paper, the modulation format is Q-ary PPM across
lasers, with intensity modulation and ideal photodetectors are assumed to
investigate the most efficient PDF models for FSO communication under turbulent
condition. The performance results are evaluated in terms of symbol error
probability (SEP) for different type of channel model and the simulation
results confirm the analytical findings.
