Analysis of NLOS Channel Properties of Terrestrial FSO Links

Point-to-point Free-Space Optical (FSO) links use narrow laser beams to transmit information in the line-of-sight arrangement. In the real atmosphere with aerosols, there is necessarily omnidirectional scattering of radiation, which gives the possibility of illegitimate reception outside the beam. This paper presents a simple qualitative model which, in addition to power levels, also describes the frequency characteristics of the eavesdropping channel. The paper also analyzes practical scenarios in terms of reception feasibility.