Improved wavelength independent empirical model for Fog attenuation in FSO communication systems

Interest in free space optics (FSO) increases day-to-day as a solution for the last mile bottleneck. The FSO link reliability is in principle sufficiently high except in severe weather conditions such as fog, dust, rain, etc. In effect, fog is until now considered as a primary challenge for FSO system because this may cause attenuation up to 480 dB/km. Fog attenuation prediction was determined by Kruse formula for long time ago. However, this formula underestimates the fog attenuation. In this paper, we improve the wavelength independent model proposed in literature for fog attenuation prediction. We determine the optimum values of the parameter k using some field measurements reported in literature. The improved model is compared and evaluated with Kruse model and others reported in literature using root mean square error (RMSE) measure. The results show good performance for the proposed model with 5 dB average RMSE lower than the lowest average RMSE achieved by other models.