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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,因此通过检测布里渊频移可得到沿光纤分布的温度或应变。长距离布里渊散射分布式光纤传感器有光时域分析和光时域反射计两种结构,虽然布里渊光时域反射计具有单端光信号处理的优点,但其传感长度受限于微弱的自发布里渊散射。而布里渊光时域分析采用的是较强的受激布里渊散射,更具有长距离传感能力。实现布里渊光时域分析的一个关键是产生传感所需的频移探测光。采用线宽小于1 MHz的光纤激光器作为单一光源,基于微波电光调制产生频移探测光,并采用正交偏振控制来抑制偏振相关信号衰弱。实现了50 km普通单模光纤的布里渊光时域分析,在10 m空间分辨率下达到约2℃的温度分辨率。
The ordinary single-mode optical fiber Brillouin scattering light, the frequency shift is a function of temperature or strain, so through the detection of Brillouin frequency shift can be distributed along the optical fiber temperature or strain. The long-range Brillouin scattering distributed optical fiber sensor has two structures of optical time-domain analysis and optical time-domain reflectometry. Although the Brillouin optical time-domain reflectometer has the advantages of single-ended optical signal processing, the sensing length is limited by Weak spontaneous Brillouin scattering. The Brillouin optical time-domain analysis using strong stimulated Brillouin scattering, but also with long-range sensing capabilities. One of the keys to achieving Brillouin optical time-domain analysis is to generate the frequency-shifted probe light needed for sensing. A fiber laser with a linewidth less than 1 MHz is used as a single light source to generate frequency-shifted probe light based on microwave electro-optic modulation, and orthogonal polarization control is used to suppress the polarization-dependent signal weakness. The time-domain analysis of Brillouin light at 50 km for single-mode fiber is achieved with a temperature resolution of about 2 ° C at 10 m spatial resolution.