Reed Solomon coded PPM for Terrestrial FSO Links

Abstract

Free space optical communications (FSO) are fast emerging as the most promising approach for addressing the emerging broadband access network and its "last mile" bottleneck. However, atmospheric attenuations and weather dependence remain the major hurdle in the wide scale acceptability of the technology. This paper proposes performance enhancement using higher state modulation schemes (i.e. 16 and 256-PPM) which promises a gain upto 25 dB when combined with RS codes as compared to the current widely used 2 state modulation mechanisms. The "RS-coded PPM" is shown as an extremely robust and well performing coded-modulation scheme for future FSO systems using a novel approach to terrestrial FSO channel modeling.