LINE OF SIGHT FREE SPACE OPTICAL COMMUNICATIONS LINK

Abstract

Free space optical communication FSO links have several features that make them attractive because they supply equip high bandwidth, high bit rates, low bit error rates, low cost, security, and it is a reliable communication medium. However, the greatest challenge for FSO communications link originates from the fundamental characteristics of free space channel; tackling these challenges requires a detailed understanding of the factors affecting optical signal propagation through free space. The aim of this paper is to provide detailed analysis of the effect of different parameters of FSO communication line of sight LOS link, including the effect of the coefficients of absorption, Rayleigh and Mie scattering, turbulence, and visibility on Propagation of Optical signal in free space for three selected types of optical sources namely Gallium Arsenide GaAs LED (850 nm), Nd:YAG solid state lasers (1060 nm), and InGaAsP laser diode (1550 nm). A numerical FSO channel model developed in MATLAB software is provided for estimating the influence of these parameters on propagation of optical signal through free space of the selected optical sources under various range and atmospheric conditions. The provided results indicate that the Rayleigh scattering is significant up to (λ=1µm), and it becomes negligible in IR band. In addition, it is proved that longer wavelength of InGaAsP laser diode (1550 nm) is less attenuated in comparison with shorter wavelengths of the other two sources.Consequently, the performance of the system at the wavelength of 1550 nm is much better than the wavelengths of 1060 nm and 850 nm.