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对于普通单模光纤的布里渊散射光,其频移是温度或应变的函数,因此通过检测光纤散射光信号的布里渊频移率,即可得到沿光纤一维分布的温度或应变。布里渊光时域分析(BOTDA)仪适合于长距离分布式传感,但存在受激布里渊散射信号的偏振相关性问题,会造成探测信号随偏振状态的随机波动,因此难以得到稳定的布里渊光频移信息。采用正交偏振控制对参与受激布里渊散射的激励和探测光信号进行偏振处理,抑制了受激布里渊散射的偏振相关性,通过检测探测光信号得到了布里渊散射光频移。最后实现了25 km普通单模光纤的分布式传感,在5 m空间分辨率下分别达到2℃的温度分辨率和30με应变分辨率。
For a single mode fiber, the frequency shift is a function of temperature or strain for Brillouin scattered light. Therefore, by measuring the Brillouin frequency shift of a fiber-scattered light signal, a one-dimensional temperature or strain along the fiber can be obtained. Brillouin Optical Time Domain Analysis (BOTDA) is suitable for long-range distributed sensing, but it has the problem of polarization dependence of the stimulated Brillouin scattering signal, which causes random fluctuations of the detection signal with the polarization state, so it is difficult to get stable The Brillouin frequency shift information. Orthogonal polarization control is used to polarize the excitation and probe optical signals which are involved in the stimulated Brillouin scattering and to suppress the polarization dependence of the stimulated Brillouin scattering. The Brillouin scattering optical frequency shift is obtained by detecting the probe optical signal . Finally, the distributed sensing of 25 km ordinary single-mode optical fiber is achieved, and the temperature resolution of 2 ℃ and the resolution of 30με are respectively achieved at 5 m spatial resolution.