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 influences of stimulated Brillouin scattering (SBS) on the sensing range of the phase sensitivity optical time domain reflectometry (φ-OTDR) was investigated and the limiting sensing range under different detection sensitivities of photodiodes was proposed. As the SBS threshold decreases along with the increasing of the fiber length, a novel scheme was presented to extend the sensing range. Circulators were employed in the scheme to divide the sensing fiber into several sections and the Rayleigh backscattering of different sections were detected by photodiodes, respectively. As a result, Stokes radiation of different sections would not affect each other such that the SBS become more difficult to build up. Therefore, the power injected into the sensing fiber increased and much longer sensing range was realized. In laboratory tests, three circulators were used to divide the sensing fiber into 3 sections, and 66.92 km sensing range was realized. The sensing range can be extend further by adding more circulators.