Line-of-sight propagation of optical wave through multiple-scatter channel in optical wireless communication system

Recently, the use of free-space optical (FSO) communications in urban environments has brought new attention to the study of optical wave propagation through clouds and fog. This application is often referred to as optical wireless communication (OWC) for the short horizontal links. The OWC links often perform poorly in adverse weather conditions such as fog and low clouds. Fog is composed of droplets of water vapor suspended in the air near the ground. These fog droplets are only a few microns in diameter, but can modify light propagation characteristics or completely hinder the passage of light through a combination of absorption, scattering and reflection. Understanding the optical propagation channel characteristics of fog will provide the critical information necessary to design OWC systems and to improve link performance.; The purpose of this study is to characterize the optical propagation channel to determine the link performance in different fog conditions. Random media such as fog in the atmosphere impede link performance by reducing available power at the receiver. We focus our study on the attenuation and wave distortion of the received signal. In a numerical study, a modified pulse vector radiative transfer (RT) equation is used to obtain the specific intensity of the received signal. We solved the equation numerically by using the Fortran radiative transfer code. Then the data was analyzed using Matlab.; We study the propagation channel characteristic by comparing the forward intensity of the received signal at different modulation frequencies, optical depths and receiver fields of view (FOVs) as a function of time. The attenuation and the phase lag cause a wave distortion in the received signal. The wave distortion induces a bit error rate, and therefore, limits the throughput of OWC communication. Therefore, if we understand the relationship between the effects of random media and the distortion in optical wave and also the effects of the communication system parameters on this distortion, we will be able to design a better OWC system to improve link performance.