Spatial Property of Optical Wave Propagation through Anisotropic Atmospheric Turbulence

Abstract

For the free-space optical (FSO) communication system, the spatial coherence of a laser beam is influenced obviously as it propagates through the atmosphere. This loss of spatial coherence limits the degree to which the laser beam is collimated or focused, resulting in a significant decrease in the power level of optical communication and radar systems. In this work, the analytic expressions of wave structure function for plane and spherical wave propagation through anisotropic non-Kolmogorov turbulence in a horizontal path are derived. Moreover, the new expressions for spatial coherence radius are obtained considering different scales of atmospheric turbulence. Using the newly obtained expressions for the spatial coherent radius, the effects of the inner scales and the outer scales of the turbulence, the power law exponent, and the anisotropic factor are analyzed. The analytical simulation results show that the wave structure functions are greatly influenced by the power law exponent $\alpha$ , the anisotropic factor $\zeta$ , the turbulence strength ${\tilde{\sigma }}_R^2$ , and the turbulence scales. Moreover, the spatial coherence radiuses are also significantly affected by the anisotropic factor $\zeta$ and the turbulence strength ${\tilde{\sigma }}_R^2$ , while they are gently influenced by the power law exponent $\alpha$ and the inner scales of the optical waves.