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根据受激布里渊散射(SBS)对相位敏感光时域反射计(φ-OTDR)的监测距离的限制,分析了在使用不同灵敏度的光电探测器时φ-OTDR系统的监测距离,并根据SBS阈值随着光纤长度的增加而下降的特点,提出了一种新的光路结构以提升系统的监测距离。该光路结构采用环行器将敏感光纤分为多个部分,并对各部分的后向瑞利散射光分别进行探测,避免了各部分光纤产生的斯托克斯光相互叠加,从而提高了SBS阈值,进而实现了提升系统监测距离的目的。在实验室测试中,使用3个环行器将敏感光纤分为了3个部分并实现了66.92 km的监测距离。通过增加环行器的数量,系统的监测距离可以进一步提高。
The monitoring distance of φ-OTDR system when using photodetectors with different sensitivities is analyzed according to the SBS detection limit of phase-sensitive OTDR (φ-OTDR) SBS threshold decreases with the increase of fiber length, a new optical path structure is proposed to improve the monitoring distance of the system. In this optical path structure, the circulator is used to divide the sensitive optical fiber into multiple parts, and the rear Rayleigh scattered light of each part is respectively detected, thereby avoiding the Stokes light generated by all the optical fibers being superposed with each other, thereby increasing the SBS threshold , And then achieve the purpose of improving system monitoring distance. In the lab test, 3 circulators were used to divide the sensitive fiber into 3 sections and achieve a monitoring distance of 66.92 km. By increasing the number of circulators, the monitoring distance of the system can be further increased.