Analysis of heterodyne efficiency of near earth coherent laser communication links

Coherent laser communication links of near space are important links of the integrated sky-earth high speed communication networks. This research focused on the heterodyne efficiency which represents coherent index of local laser and signal laser influenced by the atmospheric turbulence. The theoretical heterodyne efficiency expression with the path influenced by non-homogeneous turbulence was derived. The simulations of heterodyne efficiency of near space-earth, near space-near space and near space-low orbit satellite coherent laser communications links were given. The simulation results show that the atmospheric turbulence effect of near space-low orbit satellite links can be neglected. If the link distance between near space-near space is greater than 500 km or the zenith angle of near space to ground link is greater than 600 degrees, the heterodyne efficiency will be less than 50% and it is necessary to compensate the effect of atmospheric turbulence by using of adaptive optics.