Enhanced Performance of FSO Link Using OFDM and Comparison with Traditional TDM-FSO Link

Free space optical (FSO) communication systems with its high data rate, capacity same as optical fiber and secure communication over unlicensed spectrum have become a promising technology where the installation of optical fiber is not possible. However, bit-error-rate (BER) performance of FSO link depends on the atmospheric conditions and turbulence strength. In this paper, the performance of intensity modulation/direct detection-time division multiplexed-FSO (IM/DD-TDM-FSO) link and IM/DD-orthogonal frequency division multiplexed-FSO (IM/DD-OFDM-FSO) link are analytically compared. BER is expressed assuming the turbulence as Gamma-Gamma distribution. At BER of 10(-3), there is 14.7 dB gain in signal-to-noise ratio (SNR) and 7.2 dB improvement in receiver sensitivity with OFDM-FSO link as compared to traditional TDM-FSO link.