Ondrej Fiser

Rain attenuation measurement and prediction on parallel 860-nm free space optical and 58-GHz millimeter-wave paths

Attenuation of electromagnetic waves at 860 nm and 58 GHz due to scattering in rain is measured on the terrestrial paths simultaneously with rain intensity. The relationship between rain intensity and rain attenuation of light is analyzed using the Marshal-Palmer drop size distribution model and the Mie scattering theory. The pertinent power law model is derived from drop size distribution parameters. An empirical composite power law model is proposed and fitted to the dataset extracted from rain attenuation events recorded during a seven-year experiment in Prague. Observed average rain attenuation of light at intensities larger than about 5 mm/h is lower than attenuation predicted by standard models. Rain attenuation measured at 58 GHz is larger than attenuation at 860 nm for rain intensities in the range from 0.1 to 100 mm/h.

Long-Term Propagation Statistics and Availability Performance Assessment for Simulated Terrestrial Hybrid FSO/RF System

Long-term monthly and annual statistics of the attenuation of electromagnetic waves that have been obtained from 6 years of measurements on a free space optical path, 853 meters long, with a wavelength of 850u2009nm and on a precisely parallel radio path with a frequency of 58u2009GHz are presented. All the attenuation events observed are systematically classified according to the hydrometeor type causing the particular event. Monthly and yearly propagation statistics on the free space optical path and radio path are obtained. The influence of individual hydrometeors on attenuation is analysed. The obtained propagation statistics are compared to the calculated statistics using ITU-R models. The calculated attenuation statistics both at 850u2009nm and 58u2009GHz underestimate the measured statistics for higher attenuation levels. The availability performance of a simulated hybrid FSO/RF system is analysed based on the measured data.

Frequency and polarization scaling of rain attenuation on 58 and 93 GHz terrestrial links

First results of a propagation study focused on rain attenuation frequency and polarization scaling on 58 and 93 GHz terrestrial links are presented. Two 58 GHz links with polarization V and H and a 93 GHz link with V polarization were used. These links were operated simultaneously on an 850 m long path from December 2005 to August 2006. Individual attenuation events were compared with the concurrent meteorological situations. The records of observed rain attenuation events were statistically processed. Monthly and yearly cumulative distributions of attenuation due to rain exclusively at 58 GHz with polarization V and H, and at 93 GHz with V polarization were obtained. Obtained statistical frequency and polarization scaling of rain attenuation on terrestrial links at 58 and 93 GHz were compared with scaling calculated in accordance with the relevant ITU-R recommendations. Attenuation ratios for 93/58 GHz links and polarization ratios for 58 GHz links were obtained.

Cloud microphysics from the free space optical link point of view — Preliminary experimental results

Our experimental site is located on the top of the Milesovka hill in the Czech Republic. Low clouds reach the top of the hill very often. Using the sensor which measures the liquid water content and the particle surface area, we are able to derive the parameters of the Khrgian-Mazin model of the drop size distribution. Results of processing a few selected cloud events are shown considering the free space optical link attenuation.

Experimental Validation of FSO Channel Models

This chapter deals with the FSO link attenuation measurements at very special (severe) climatic conditions of the mountain Milesovka observatory being appropriate for the research but being not typical one. Therefore, examples of measurements from Prague, Budapest, and Milano are added. Fog attenuation (in combination with cloud) is discussed and Kim formula predicting the fog attenuation from visibility was more or less acknowledged. More accurate results are provided for rain attenuation estimation using the Carbonneau formula. Examples discussing concurrent occurrence of rain, fog, and clouds are analyzed. In the last part, we analyze the attenuation due to atmospheric turbulences concluding that the Rytov formula overestimates the attenuation on one hand, but is in good correlation with the measured attenuation on the second hand.

Propagation characteristics obtained on parallel terrestrial FSO links at 860 nm and 1550 nm

Attenuation due to hydrometeors on two parallel terrestrial free-space optical links working at 860 nm and 1550 nm on an 853 m long path and concurrent meteorological measurements were processed over a one-year period. Attenuation events were classified according to the types of hydrometeors that occurred. Both the attenuation and meteorological data were statistically processed and the obtained cumulative distributions of attenuation due to hydrometeors are presented. Cumulative distributions of lower visibilities due to individual hydrometeors as well as cumulative distributions of hydrometeor intensities are also given. The results obtained are discussed.

Specific Results of 7-Year Hydrometeor Attenuation Research at 58 GHz on an 850 m Terrestrial Path

The results of 7 years of experimental research of attenuation due to hydrometeors at 58 GHz with V polarization on an 850 m path are presented. Both the cumulative distributions of attenuation due to all the hydrometeors together and the cumulative distributions of attenuation due to the individual hydrometeors are given. The influence of the individual hydrometeors on attenuation is assessed. The cumulative distribution of rain attenuation obtained for the 7-year period of observation is compared with the one calculated for the average year in accordance with relevant ITU-R recommendations.