| Brillouin scattering-based optical fiber sensing technology can provide measurements of high precision, long distance, low cost, which are broadly used for structural health monitoring such as tunnel, bridge and civil engineering. It has been the hotspot in the field of optical sensing technologies. Brillouin Optical Time Domain Reflectometry (BOTDR) is one of the most important spontaneous Brillouin scattering-based sensing technologies. It can measure the temperature and strain along the fiber and only need one end to perform detection.In this paper, by using the method of signal processing, theoretical research and experimental verification are carried out to improve the performance of BOTDR. The iterative subdivision method is firstly proposed to improve the spatial resolution of BOTDR. By analyzing the process of generation of Brillouin scattering signal, the power density distribution is derived. The Brillouin signal is divided based on the power density distribution. Experiments show that this method can obtain 1.5m and 0.1m spatial resolution in 50km and 1km fiber respectively.A maximum similarity matching method is proposed. The correlation coefficient is selected as the similarity evaluation function in the method. By evaluating the similarity between the reference spectrum and the detection spectrum, the Brillouin frequency shift is obtained. Experiments verify the feasibility of the method. Compared with fitting method, this method is not limited by the profile of the Brillouin spectrum and can get more precise results and higher speed. |
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