Dispersion Analysis of 1.55um Free-Space Optical Communications through a Heavy Fog Medium

Free-space optical communication (FSOC) is a method by which one transmits a modulated beam of visible or infrared light through the atmosphere for broadband applications. FSOC makes connectivity possible between high-rise buildings and metropolitan and intercity communication infrastructures. While radio frequency (RF) communication still dominates the commercial communications networks, it has not been able to meet the increasing demand for larger data rates. Reliable communications require a good understanding of the surrounding environment that affects the communications channel. The fundamental limitation of FSOC arises from the environment through which light propagates. The presence of particles, such as fog and clouds in the propagation channel introduces spatial and angular dispersion to the transmitted light signals. Attenuation of the light signals through the propagation medium is a combined effect of dispersion and absorption by particles. A mode of ray tracing is developed to simulate light going through the medium. A 2-D histogram is presented to investigate correlation of spatial and angular dispersion of the received light.