Model for the Prediction of Rain Attenuation Affecting Free Space Optical Links

Abstract

A model for the prediction of the attenuation induced by rain on free space optical (FSO) links is presented. The proposed methodology is developed, starting from the accurate simulation of the interaction between FSO links (path length up to 5 km) and precipitation maps, from which analytical expressions are then proposed. The model is simple as it only receives the local rainfall statistics for the site of interest as the input, but it is also accurate, as it takes into account the dependence of the attenuation on the drop size distribution (DSD), as well as multiple scattering effects associated with rain, which contributes to reducing the overall predicted attenuation. The proposed model represents a useful tool to dimension FSO links in areas where fog is negligible, i.e., where rain has the highest impact on the link performance.

A Survey of Free Space Optics (FSO) Communication Systems, Links, and Networks

“…In the case of European region, the climate is prone to fog and heavy snow, which directly affects a FSO link [7]. However, in Malaysia, which is located within tropical climate, snow does not exist, fog is not a considerable concern, whereas haze and heavy rain are foreseen to significantly impact the availability of a FSO link [75].…”

“…Currently, the new recommendations (e.g. P.837-6) [75], [84] include highly precise models to predict the rain rate statistics according to regions throughout the world. Globally, rainfall is subdivided into fifteen climatic zones by ITU according to the rainfall intensity of (mm/hr) for each region.…”

A Survey of Rain Attenuation Prediction Models for Terrestrial Links—Current Research Challenges and State-of-the-Art

“…Another technique for generating the rain rate is applying the local rain data to the MultiEXCELL model [ 23 ]. This model was used in [ 24 ] to generate synthetic rain rates. Transmitting and detecting specific differential phase-shifted signals through a dual-band radar system has been experimented with in [ 25 ].…”

Experimental Study of the Free Space Optics Communication System Operating in the 8–12 µm Spectral Range

“…The main advantage of FSOs is their wide application field that includes outdoor wireless access, backhaul, fiber backup, last mile [4,5], bridging Wide Area Network (WAN) [6], and military access [7]. Several factors can significantly reduce the transmission efficiency, in particular, physical obstructions, rain [8], temperature fluctuations in different air layers [9], geometric losses [10], absorption [11], atmospheric turbulence [12][13][14], and atmosphere attenuation and scattering [15]. In commercial FSO communication systems, strictly defined wavelengths of approximately 0.8 µm and 1.5 µm are used [16,17].…”