FSO system performance evaluation based on calibrated atmospheric channel emulation

A novel approach for testing Free Space Optical (FSO) systems in a controlled laboratory condition is proposed. Based on fibre optics technology, our testbed could effectively emulate the operation of real wireless optical communication systems combined with various atmospheric perturbation effects such as fog and clouds. The suggested architecture applies an optical variable attenuator as a main device representing the tropospheric influences over the launched Gaussian beam in the free space channel. In addition, the current scheme involves an attenuator control unit with an external Digital Analog Converter (DAC) controlled by self-developed software. To obtain optimal results in terms of the presented setup, a calibration process including linearization of the non-linear attenuation versus voltage figure is performed. Finally, analytical results of the attenuation based on real and simulated measurements with the hardware channel emulator (= testbed) in a laboratory controlled environment are shown.