Mitigation of scintillation in FSO using aperture averaging of partially coherent input Gaussian optical beam

Abstract

Atmospheric turbulence induced scintillation of a partially coherent transmitted optical beam in a point-to-point Free Space Optical (FSO) communication system have been investigated. Effects of aperture averaging in mitigating the fluctuations of the optical beam profile reaching the photo-detector have been studied under i weak ii moderate ii strong turbulent conditions. The combined effect of partially coherent optical beam and aperture averaging at the receiver were compared for different values of the aperture widths. Semiconductor optical sources emitting in the range 780–1550 nm were taken to observe the influence of wavelength in mitigating the scintillation effects using aperture averaging. Performance of the optical communication link was studied using MATLAB simulation programs for the three turbulent situations. Results are graphically presented to explain the effects of aperture averaging factor A and the aperture radius scaled by Fresnel zone between the trans-receiver systems in reducing the scintillation effects in FSO system. It is observed that a partially coherent Gaussian with 1550 nm wavelength with 40–50% reduced diameter will obtain a desired minimum level of scintillation index at a particular turbulence condition.