| Distributed optical fiber sensor system can sensing the change of temperature along the optical fiber by the form of continuous function of distance. The fiber of distributed optic fiber has the peculiarity of insulation and resistance of electromagnetic interfere, small size and do little effect to temperature field. The distributed optic fiber sensor is always the hotspot in industry, science , military affairs and other fields.Deep research is taked on the distributed optic fiber temperature sensor in this thesis,and the distributed optic fiber sensor based on the Raman scattering is adoptioned. The work theorem of the distributed Raman optic fiber temperature sensor system is introduced in this thesis; and the predominant technology index impacted on the capability of the distributed Raman optic fiber sensor is assayed and the system of distributed Raman optic fiber sensor is devised.The principle of Raman scattering and of distributed optic fiber temperature measuring methods has been researched and three demodulation methods have been discussed. The back scattering Raman signal with the information of temperature is weak or completely submerged in noise. The temperature calibration methods of distributed optic fiber temperature sensing system was discussed and a new method was brought forward .As a result, the denoising level determined the accuracy of the whole system. Weak signal measurement must be used in this system and resolved the remaining problem and the signal collection block is devised.Based on the theorem of distributed temperature measuring,the factor about the accuracy of temperature was discussed . A signal processing method was discussed based on the study of distributed temperature. The thereunder of theoretics about how to choice the wavelengh was broung forward. This method is the amalgamation of signal processing system and average, which can raise the signal-to-noise ratio and improve the accuracy of system. |
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