Turbulence spectrum model and fiber-coupling efficiency in the anisotropic non-Kolmogorov satellite-to-ground downlink

Abstract

Increasing experimental and theoretical results have confirmed that the anisotropy of turbulence cells cannot be ignored in the atmospheric turbulence. The satellite-to-ground downlink is the important part of satellite optical communication network, so the anisotropic non-Kolmogorov turbulence spectrum model for the satellite links needs to be established urgently. However, the previously derived turbulence spectrum model for the satellite links is only applicable to vertical links. In this paper, considering the ellipsoid hypothesis of turbulence cell, we derive a new anisotropic non-Kolmogorov turbulence spectrum for the satellite links that is applicable to both vertical and slant links. Then based on this spectrum, the fiber-coupling efficiency for a Gaussian-beam propagating through the weak-to-strong anisotropic non-Kolmogorov satellite-to-ground downlink is developed. The results show that when the zenith angle is greater than a certain angle, the coupling efficiency decreases with the rising of anisotropic factor, but while the zenith angle is less than the certain angle, the opposite trend will appear. It is anticipated that this work will benefit the understanding of laser beam transmission in the anisotropic non-Kolmogorov satellite links and provide the theoretical basis for the design and parameter optimization of satellite optical communication systems based on fiber-coupling.