A comparison between free space optics and 70 GHz short haul links behavior based on propagation model and measured data

Free Space Optic (FSO) has been confirmed as a valid alternative technology [l] that gives the opportunity to implement in a very quick way digital links with capacity up to some hundreds of MBit/sec without the need of license and minimizing installation operations and interference issues. On the other hand we??ve to keep in mind that these systems arc designed to perform , np to some km , in clear weather conditions and , up to now, there is no escape from visibility impairments related to haze, fog, rain, hail and snow. During these phenomena the significant increase of scatter losses can produce unavailability periods that can last some hours in case of fog. On the other hand 70 GHz radio links are mainly affected by rain and snow. The relation between visibility and extinction coefficient ( scatter and absorption losses ) together with its statistical characterization depending on the adopted wavelength are essential for the calculation of an adequate fading margin necessary in order to reach high reliability targets for both the systems.