Smoke attenuation in free space optical communication under laboratory controlled conditions

In this paper, we present the experimental results on smoke attenuation for a free space optical communication link. The smoke is generated in an indoor atmospheric chamber under the laboratory controlled conditions. Theoretical simulations are carried out in order to verify that the homogeneity of smoke inside the atmospheric chamber can be improved by increasing the link length. This is achieved by the optical beam being bouncing back and forth between optical mirrors. The improved homogeneity in smoke enhances the accuracy in evaluating the visibility V to characterize smoke and thus the resultant attenuation of smoke. The experimental results for attenuation of FSO communication systems operating at the visible and near infrared (NIR) wavelengths (0.6 μm <; λ <; 1.6 μm) in the controlled laboratory based smoke environment are also presented and compared to the theoretical smoke model. Results indicate that smoke attenuation is wavelength dependent for dense smoke conditions for V <; 0.5 km. Smoke attenuation is higher at the visible wavelength than the near infrared wavelength. The measured attenuation of smoke is almost 90 dB/km for the visible range and 43 dB/km at the NIR wavelength range for V = 0.185 km.