Multiple Wavelength Free-Space Laser Communications

Abstract

Free-space optical communications systems in the atmosphere, based on intensity modulation and direct detection, are heavily affected by fading caused by turbulence cells of varying scale and motion. Several data sets of fading measurements under different scenarios have been recorded demonstrating this effect. In this paper we introduce a form of free-space laser communications involving a source operating on several wavelengths. The goal is to overcome atmospheric interference on a communications link. We have performed simulations using the DLR PILab Matlab toolbox. These indicate the extent to which the turbulence and beam properties interact. Experimental investigations are planned. Further properties are also taken into account, including the choice of appropriate laser bandwidth and wavelengths, the effect of atmospheric absorption from aerosols and molecular absorption lines, as well as effects of atmospheric structure on beam propagation. Possible scenarios for application of this scheme will be presented as well.