Analytical performance evaluation of a RF subcarrier modulated optical FSO system under the influence of atmospheric turbulence

An analytical approach is developed to evaluate the carrier to noise ratio and bit error rate of a free space optical link with RF subcarrier modulation taking into account the effect of weak atmospheric turbulence which is modeled as log-normal distribution. A close form expression for the carrier to noise ratio conditioned on a given turbulence at the output of a direct detection is developed. Average CNR and BER are then evaluated by averaging the results are evaluated in terms of bit error rate and power penalty suffered by the system due to turbulence at a given BER for several system parameters link turbulence variance, system parameters like turbulence variance, link distance, data rate, RF modulation index etc.