Mean Fade Time of an Optical Communication Channel Under Moderate-To-Strong Atmospheric Turbulence.

摘要

Interest in the use of optical communications over terrestrial links has greatly increased during the last several years. In many applications, the path is horizontal so the index of refraction structure parameter can be taken as constant. In addition, optical communication channels offer a number of advantages over conventional RF channels. However, due to the short wavelength, the reliability of an optical link can be seriously degraded over that of an RF system by atmospheric scintillation. In particular, scintillation can cause severe fading of the channel. In our analysis here we assume that the refractive index structure parameter C_n~2 is constant and use our recently developed gamma-gamma model and the well known lognormal model to consider the fading statistics associated with a spherical wave model for simplicity. The results are similar to a Gaussian-beam wave with perfect pointing.Our analysis show that compared to the gamma-gamma model, the lognormal model predicts optimistic values of probability of fade, underestimate the number of fades per second and consequently does nto measure the mean fade time correctly.