الفهرس يوجد فقط 14 صفحة متاحة للعرض العام
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المستخلص
Free Space Optical communications or FSO is a telecommunication technology that uses light propagating in free space to transmit data between two points. The technology is useful where the physical connection of transmit and receive locations is difficult, for example in cities where the laying of fiber optic cables is expensive. FSO might also be used to communicate between ground to spacecraft/satellite or between spacecraft/satellite to spacecraft/satellite.
With recent advances and interest in Free Space Optics for commercial deployments, a proper understanding of optical signal propagation in different earth’s atmospheric conditions has become essential, and thus arises the need to rationalize the effects of atmospheric channel on FSO links. This atmospheric channel acts as multiply scattering media that may be due to cloud, haze or rain.
The aim of this thesis is to present the results of our effort to simulate the atmospheric FSO channel. We considered the study of the response of the optical cloudy channel to an optical signal which is delta in time, space, and angle. We chose to simulate the cloudy channel only because it is the biggest environment challenge for an FSO link. This studying is important to predict the performance of a FSO link operating under cloudy conditions.
In this thesis, we concentrated on the study of the temporal, spatiaJ, and angular dispersion of the transmitted optical signal due to the physical characteristic of the cloudy channel. We chose the cloud microphysical parameters (i.e. scattering particles, particle-size distribution, concentration of particles ... etc) to approximate the low altitude clouds.
To solve the problem of light transport in this cloudy atmosphere, we assumed that the light consists of mono-energetic photons. We used the Monte Carlo method to deal with the analysis of the propagation of these photons at a specified optical wavelength. Based upon this Monte Carlo method, we constructed a stochastic radiative transfer model. This model was based on the forward-propagating photon transport algorithm, and the response of the cloud is then calculated by using the concept of the local estimation method. So, the properties of the radiation field can be obtained at any desired point in the cloud model domain.