This paper is a first attempt to study the effects of atmospheric turbulences on hybrid free space optics/ radio frequency (FSO/RF) transmission system in Doha, Qatar. The state of Qatar is characterized by a Mediterranean climate with hot and dry summers with modest cloud coverage highly affected by airborne dust. Due to its sensitivity to atmospheric turbulences, throughout this study, we try to demonstrate the working capabilities of FSO technology as well as to promote an understanding of this technology amongst the countries of the gulf cooperation council (GCC). Moreover, we studied the behavior of RF link during the same period. In order to analyze the transport media, two transmitting subsystems are employed and installed at Qatar University (QU) at two different buildings separated by a distance of 600 m. Each system is composed of a FSO and RF terminal. We have ported an Embedded Linux kernel on Micro-blaze processor build in Field Programmable Gate Array (FPGA). Then, we have designed a network sniffer application that can run on the FPGA board. The measurements from the network sniffer applications were carried out during summer season from June up to September 2015. The relation between the measurements and the atmospheric factors, taken from a weather station installed at QU, were also found.
KEYWORDS: Free space optics, Signal attenuation, Free space optical communications, Optical communications, Laser systems engineering, Infrared radiation, Visibility through fog, Visibility, Data modeling, Atmospheric modeling, Optical sensors, Atmospheric optics
In order to distinguish the most rigorous model, we made a comparison between measurements data and the mostly used empirical models. These models use the visibility as a basic parameter to predict the fog attenuation. In order to measure the visibility, we used a laser lamp of 532 nm and two light sensors. The experimental set up is composed of a fog machine and two KORUZA terminals operating at 1310 nm and 1550 nm, respectively. Every one minute, the measured attenuation is averaged to one value then compared to the attenuation calculated based on measured visibility and according to the empirical models cited previously.
The LASERIX facility provides coherent and short soft x-ray beams for scientific applications. The beams are generated through high intensity laser interaction with matter using two different schemes, plasma based soft x-ray lasers, and high order laser harmonic generation. We describe in this communication the present status
of the facility. The LASERIX beamtime has been recently opened to external users. We present two typical experiments performed in that context with the facility. The first one is dedicated to the fundamental study of the plasma based soft x-ray laser, whereas the second uses the existing beam to study irradiation induced
dammage in DNA samples. We present also the development performed on the soft x-ray laser source to improve its stability and high repetition rate operation.
S. Liehn, C. Le Sech, E. Porcel, B. Zielbauer, J. Habib, S. Kazamias, O. Guilbaud, M. Pittman, D. Ros, M.-A. Hervé du Penhoat, A. Touati, H. Remita, S. Lacombe
Samples of plasmid DNA were irradiated with pulsed 18.9 nm radiation originating from a Mo X-ray laser (XRL)
pumped in GRIP configuration at the LASERIX facility. Up to 21 000 pulses were delivered with a repetition rate of 10
Hz and average pulse energy of 200 nJ. Radiosensitization by two different platinum compounds (platinum terpyridine
chloride (PtTC) and platinum nanoparticles) were investigated. SSB and DSB yields were measured using agarose gel
electrophoresis. The occurrence of single and double strand breaks not present in controls having undergone the same
treatment except for the XRL irradiation can be seen as a clear effect of the XRL irradiation. This confirms the role of
direct effects in DNA damages as previously seen with low energy ions and electrons (1) (2). In addition we demonstrate
a DNA breaks enhancement in the presence of platinum. No difference of enhancement was seen between these two
radiosensitizers.
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