Abstract: FSO is communication system where free space acts as a medium between transceivers and they should be in LOS (line of sight) for successful transmission of optical signal. Medium can be air, outer space or vacuum. This system has many advantages like high bandwidth, no spectrum license and economically less. The transmission in FSO is dependent on the medium because the presence of foreign elements like rain, fog and haze, physical obstruction, scattering and atmospheric turbulence are some of these factors. There are many routing techniques available for the transmission of light wave in free space. A comparative study of different routing techniques used in FSO is discussed in this paper.
Keywords: FSO, Link margin, RWA, modulation, routing, nodes, routing techniques.