Spatially multiplexed OFDM – RoFSO transmission under different atmospheric conditions

Abstract In this paper, a spatially multiplexed, OFDM-based radio over free space optical (RoFSO) communication system is proposed to enhance the data rate. The input data streams 1–4 are combined using space division multiplexing (SDM) to achieve 80 Gbps (4 × 20 Gbps) transmission rate. At SDM level, an optical carrier of 193.1 THz frequency is selected and various Laguerre Gaussian (LG) modes LG00, LG01, LG02, and LG03 are assigned to individual data streams 1–4. The RoFSO link is analyzed for different atmospheric attenuation and turbulence conditions while measuring system bit error rate (BER), Q-factor, received signal power, signal to noise ratio (SNR), etc. A comparative analysis for back to back (B2B), subcarrier multiplexed (SCM-MUX), wavelength division multiplexed (WDM-MUX), and space division multiplexed (SDM-MUX) configuration is carried out. In FSO environment, the SDM-MUX configuration is further analyzed for various haze, rain, fog, and dust conditions. Analysis shows that the extended link range is observed under low attenuation conditions. The impact of atmospheric turbulence under light rain and heavy rain conditions is also analyzed. The overall analysis estimates higher transmission rate for SDM-MUX configuration. Also, channel capacity can be enhanced by introducing additional optical modes for the selected design configuration.