Study On The Characteristics Of Non-line-sight Propagation Of Polarized UV Radiation In Atmosphere

Non-line-of-sight (NLOS) UV communication is an exciting application of free-space-optical (FSO) communication recently, it makes use of solar-blind UV as the communication wavelength to obtain all-day work, makes use of scattering of light by atmospheric particles to achieve NLOS propagation, and is an method of optical communication which can work at NLOS geometry. The main aims of this paper are to find a method that can measure the intensity and polarization of the signal of NLOS UV communication, and to find a way to enhance the performance of UV communication. The main conclusions are shown as follows:The polarized scattering models are set up. The signal of UV communication has two characteristics: intensity and polarization, but the existing scattering models, including the single-scatter models based on the spheroidal coordinate system and the multiple-scatter models based on Monte Carlo, can not calculate the polarization of the signal. By extending the existing unpolarized scattering models to polarized ones, the polarization of the scattering signal, and also the impact of the polarization setups on scattering signals, can be calculated quantitatively.The conception and the structure of polarized UV communication have been presented, and the elementary experiment have been done. The existing NLOS UV communication system can only measure the intensity of the signal, and the data rates are mostly among the range of several kilo bps to several tens of kilo bps, which are violently lower than the theoretically predicted data rates. By the means of measuring the intensity and polarization at the same time, the data rates of the existing systems can be greatly enhanced, this is the so-called polarized UV communication. The polarized UV communication system consists of a light source accompanied with a time-dependent polarizer and a detector array accompanied with a time-independent analyzer array; the polarizing information is coded by the polarizer, influenced by the atmospheric channel, analyzed by the analyzer array, and decoded according to the distribution characteristics of the scattering signals on the detector array. The decoding of the polarizing information for 2-polarization UV communication is validated by the experiment.The calculation process of the single-scatter model based on the prolate spheroidal coordinate system is simplified; the empirical formula of the single-scatter energies in the coplanar geometries is presented. The noncoplanar single-scatter model presented by Elshimy can solve arbitrary transmitter-receiver geometry, but the complicated calculation process may restrict its application; the calculation process is greatly simplified, thus the model is more tractable than before. In the empirical formula of coplanar unpolarized single-scatter energy, the impacts of the transmitter-receiver geometry, the atmospheric parameters, and the range to the single-scatter energy are very clear, this formula can be used for the design guidance of short-range UV communication system.