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Research On The Theory Of Apperceiving Underwater Information With Brillouin Scattering

Posted on:2005-03-02Degree:MasterType:Thesis
Country:ChinaCandidate:Y GaoFull Text:PDF
GTID:2168360152968493Subject:Physical Electronics
Abstract/Summary:PDF Full Text Request
Brillouin scattering Lidar underwater detection technique is an application in underwater detection that combines Brillouin scattering with Lidar and remote sensing technique. The detection mode is new and the accuracy of measurement is comparatively high, the new detection way is more feasible and practical. This new technique is not only able to detecting the sound speed, the salinity and the depth of the sea, but also can be applied to identifying target, i.e. identifying whether there are torpedo and submarine etc underwater, which has great sense and importance for us to understand ocean and solidify our national defence. Brillouin scattering Lidar underwater detection system involves Brillouin scattering, Brillouin frequency shift, i.e. Brillouin Lidar system and edge technique. Brillouin scattering is a phenomenon which is caused by the interaction of incited light and elastic sound wave of the medium, the primary characteristic of Brillouin scattering is that the scattering light has a frequency shift relative to the incited light. Detecting the small frequency shift is the key of Brillouin scattering Lidar underwater detection system. The edge technique is a new and powerful method for measuring small frequency shifts, in particular it can be applied to obtain underwater Brillouin frequency shift with a Brillouin Lidar system. The intensity and its angular distribution of Brillouin scattering has get much attention, especially in ocean detection with Brillouin scattering. The Brillouin scattering cross section is deduced. Classical electromagnetic and quantum electrodynamics theory,the two ways in depicting the physics process of Brillouin scattering underwater are compared and discussed intensively. This paper emphasizes the edge technique. Some theoretical analysis on Brillouin frequency shift determination with the edge technique is given. From theoretical calculations, the effect on the measurement of Brillouin frequency shift,which are caused by the absorption line of the ideal molecular absorber,is analyzed. The relations of Brillouin frequency shift B and the oceanic backscattering signals ratio S is also discussed. The resulting signals ratio S is plotted in a series of figures under different center frequencies and different widths of the absorption lines.Lastly the statistic error of Brillouin frequency shift measurement and accuracy of sound speed measurement are analyzed. The maximal detecting depths of sound speed was calculated under different system conditions. These data may contribute to the design of Brilluin Lidar.
Keywords/Search Tags:Laser, Brillouin scattering, Scattering cross section, Brillouin frequency shift Edge technique, Molecular absorber
PDF Full Text Request
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