Analysis of the influence of the particle surface area (PSA) for optical wireless links under fog conditions

The influence of fog on optical wireless links is highly depending on the used wavelength. Experiments, measurements and simulations showed much lower attenuations on larger wavelengths (up to 10 μm). These results play an important role for the corresponding use of FSO links starting from terrestrial links towards space applications. It is intended to interconnect well-proved technologies like 850 nm and 1,064 nm wavelength with new technologies under development (like 10 μm wavelength). Since every technology comes with different properties, it makes sense to have a deeper look on the fog analysis. Practical results within COST Action IC 0802 are implemented in the modelling of the FSO channel under deteriorating fog conditions and other atmospheric effects. TU Graz scientists analysed together with colleagues from Milan and Prague simultaneously measured data of the liquid water content (LWC), integrated particle surface area (PSA), visibility and optical attenuation on different locations. The parameters have been used to analyze the effects of PSA on optical attenuation caused by fog particles. Optical attenuation has been measured at two different wavelengths (830 nm and 1550 nm) across co-located links. Five months measured data have been analyzed to observe the variation and effects of PSA over the fog microphysical parameters (visibility and LWC) and optical attenuations caused by fog. To investigate the influence of fog to analyse the resulting attenuations (measured at Graz, Milan and Prague in detail) and to know the fog microphysics and its characterization for different wavelengths will improve future Optical Wireless Systems.