Stimulated Raman Scattering In Fibers And Its Application

Stimulated Raman scattering (SRS) is one of the most important problems in the field of non-linear fiber optics. Recently the Raman fiber laser and Raman fiber amplifier with their special characters have attached much more attentions. Therefore the investigation about Raman scattering of fiber has become a hot research problem in the area of nonlinear optics.In the dissertation, we mainly investigate the spectrum characters and polarized properties of SRS in fibers. Compare the experimental result of plastic optical fiber with that of silica fiber. Then we go further into its application in detecting to microscale gases. The whole paper can be taken into three parts: the theory of stimulated Raman scattering, the spectrum characters and polarized properties of SRS in fibers, and the application of Raman scattering in detecting.In the first part, we sum up the recent development of stimulated Raman scattering, and introduce the achievement of SRS in fiber and the position of Raman scattering in spectrum. Then we analyze the physical mechanism of stimulated Raman scattering, study the laws of the Stokes spectrum intensity changing.In the second part, we systematically study the spectral characters of stimulated Raman scattering in silica optical-fiber and plastic optical-fiber, then measure the threshold, spectrum width and Raman gain of SRS. The mechanism of energy transmission between each order of the Raman spectra is analyzed. The temperature character of Raman spectra in silica fiber is studied. For the first time the first order SRS spectrum of PMMA plastic fiber is gained and the frequency-shift, threshold, spectrum width are also gained. Then compare the experimental result of plastic optical fiber with that of silica fiber. The result indicates that the plastic fiber and the silica fiber have the same mechanism of energy transmission.The energy density of plastic fiber at the point of threshold is much lower than that of silica fiber.The polarized light properties of SRS in circular core and elliptical core silica opticalfiber are systematically studied. The parameter such as polarized light properties and the Raman frequency-shift and so on under the condition of different pump light state is analyzed. The experience formula is provided. Each -order Stokes spectra polarization states of stimulated Raman scattering in the birefringence optical fiber are related not only with Raman medium but also with pump light polarization state. The influence of pump light polarization state on low-order Stokes frequency-shift is lower but higher on the high-order Raman Stokes frequency shift fluctuation.In the third part, we discus the principle of detecting pollutant air by using the method of Raman amplification in fiber. A new method of testing trace gases and measuring their concentration is given. By using this method low weak signal light can be amplified and extracted. Therefore trace gases of low concentration can be detected.