Irradiance fluctuations of an indoor FSO channel based on hot air chambers

In this paper the fourth order statistical momentum behavior of irradiance fluctuations through hot air chambers which is crucial for evaluating the proper performance of optical turbulence generator (OTG) as a laser communication channel is studied. Basic principles of designing a developed free space optical wave propagation channel are presented. In order to validate the OTG performance with respect to the real atmosphere, beside Kolmogrov statistics presumptions like homogeneity, isotropy, stationarity and ergodicity, random fluctuations of the signal due to atmospheric turbulence is investigated and compared with log-normal and gamma-gamma PDF model. We have shown the above properties for our OTG and 2/3 power law behavior for the temperature structure function according to the Kolmogrov theory. Experimental data of irradiance fluctuations are well corresponds to the log-normal and gamma-gamma distributions under proper wind velocities and chamber active area. Therefore the chamber irradiance fluctuations resemble more accurately to the real atmosphere. Atmospheric parameters of the turbulence in different wind speeds and channel widths are estimated by new method of fitting the theoretical PDF to the experimental intensity irradiance distribution. The irradiance fluctuations again temperature difference and turbulence strength is measured and compared with the theory.