Analysis of Beam Wander Effect of Flat-topped Multi-Gaussian Beam for FSO Communication Link

Atmospheric turbulence causes severe impairment of FSO communication link. By using the earlier model for the Gaussian beam, we analyze the beam wander effect for the flat-topped multi-Gaussian beam. The link availability decreases drastically in high turbulence regime for a Gaussian beam due to turbulence induced beam wander. In this paper, we model each turbulent eddy as a thin dielectric lens with Gaussian shaped refractive index profile and assume there are several sheets of eddies throughout the propagation path. We consider uniformly distributed eddy positions in a laminar sheet with Chi-Square distributed eddy sizes. We graphically demonstrate beam wander characteristics for different beam sizes and orders of the flat-topped multi-Gaussian beam in all three turbulence regimes characterized by different refractive index structure parameter values. Our results show that the flat-topped beam has a limited advantage in weak and moderate turbulence regimes. But it has a significant advantage in high turbulence regime to mitigate link outage due to beam wander.