Thirdly, the fog attenuation for Gauss beam propagation is discussed, and the computational results are compared with those with plane wave incidence.

The most typical weather restriction of Free-space Optical Communications System is the fog; the fog attenuation of laser is a main factor that affects the performance of the lasers communication.

We get rules of the attenuation of fog, cloud, haze and atmosphere as the height changes, and give the calculation formula of the laser scattering character of cloud layer.