Radio on free space optics has become a momentum in research because of its cost effectiveness and efficiency in transferring data at a high rate that is comparable to that for optical fiber media. The transmission data rate is limited in fiber due to dispersion and nonlinearity, such effects do not prevail in FSO communication links. The data rate depends mainly on the switching speed of the optoelectronic devices. With the characteristics of free space being random in nature, the performance of RoFSO is primarily governed by atmospheric conditions. In this report, the performance of the orthogonal frequency division multiplexing (OFDM) signal in free space is evaluated and compared against its counterpart radio frequency (RF) wireless communication systems. Simulations have been done on the atmospheric conditions by means of modeling the scintillation effect using log-normal distribution. Theperformance of the proposed system under two different baseband modulations, namely OFDM–PSK (phase shift keying) and QAM (quadrature amplitude modulation) in weak turbulence conditions is studied. It is found that PSK performs better than QAM. Also the M-ary performance analysis shows that 3–5 dB improvement in the signal to noise ratio is obtained for OFDM based FSO transmission compared to RF based wireless transmission.
Keywords: Optical wireless communication, Radio frequency, Free space optics.