Title: Mitigation of scintillation in FSO using aperture averaging of partially coherent input Gaussian optical beam
Authors: Sachin M. Kale; Asim Kar
Addresses: Department of Electronics and Telecommunication Engineering, Jadavpur University, Kolkata 700032, India ' Department of Electronics and Communication Engineering, Institute of Engineering and Management, Kolkata 700091, India
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 iii) 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.
Keywords: FSO communications; free space optical; LANs; local area networks; SNR; signal to noise ratio; BER; bit error rate; scintillation index; aperture averaging; Gaussian optical beam; partially coherent optical beam; turbulence; simulation.
International Journal of Signal and Imaging Systems Engineering, 2014 Vol.7 No.1, pp.21 - 29
Received: 05 Feb 2011
Accepted: 19 Apr 2011
Published online: 24 Oct 2014 *