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由于探测光脉冲宽度受到限制,布里渊光时域反射仪(BOTDR)在对光纤上的应变进行分布式测量时,空间分辨力只能达到1 m。针对布里渊光时域反射仪单次采样接收背向布里渊散射信号(BBS)需要一定的时间,提出了基于等效脉冲光的多洛仑兹拟合法以提高其应变测量的空间分辨力。该方法将探测光脉冲在布里渊光时域反射仪完成单次采样所需的时间上进行积分,将积分函数作为等效脉冲光的表达式,再根据等效脉冲光的形状将布里渊光时域反射仪接收到的背向布里渊散射谱(BBS)细分,并对它进行多洛仑兹迭代拟合,准确求得每个细分布里渊散射谱的中心频率,进而利用光纤中布里渊频移与应变的对应关系,得到光纤中与细分布里渊散射谱对应的细分光纤单元上的应变情况。实验结果表明,利用这种方法,可使布里渊光时域反射仪应变测量的空间分辨力提高至0.05 m。
Due to the limited pulse width of the probe light, the Brillouin Optical Time Domain Reflectometer (BOTDR) can only achieve spatial resolution of 1 m in distributed measurements of the strain on the fiber. For Brillouin optical time-reflectometer single-sample receiving back-to-Brillouin scattering signal (BBS) takes some time, the equivalent pulsed light based on the Polynon fitting method to improve the spatial resolution of the strain force. The method integrates the probe light pulse in the time required for Brillouin optical time-reflectometer to complete a single sampling, integrates the integral function as the expression of the equivalent pulsed light, and according to the shape of the equivalent pulsed light, Back-facing Brillouin Scattering Spectra (BBS) subdivision received by the deep-light time-domain reflectometer, and it is subjected to the polynomial iterative fitting of the polynomial to obtain the center frequency of each subdivision Brillouin scattering spectrum accurately By using the corresponding relationship between the Brillouin frequency shift and the strain in the optical fiber, the strain on the subdivided optical fiber unit corresponding to the finely distributed Brillouin scattering spectrum is obtained. The experimental results show that the spatial resolution of the strain measurement of Brillouin OTDR can be improved to 0.05 m by this method.