介绍了一种基于马赫-曾德尔(M-Z)和萨格纳克(Sagnac)混合干涉仪原理的分布式光纤泄漏检测系统，阐述了系统的工作原理及对泄漏点的定位方法。分别在空气和水下环境中进行实验，并分别在泄漏点距离法拉第旋转镜4025、7043、9050 m 处进行实验，检测不同环境以及不同泄漏点位置对检测系统的影响。在泄漏点距离法拉第旋转镜为7043 m 处重复做了20 次实验，测试检测系统的精确度。实验结果表明：在水下环境中实验所得的干涉信号频谱强度较大，频带较宽；泄漏点距法拉第旋转镜越远，实验结果所得的绝对误差越大；系统能够检测出管道内气体压力为0.5 MPa，泄漏孔径为2.5 mm 的微小泄漏信号并对泄漏点定位，平均相对定位误差为1.44%。

An interferometric distributed fiber optic leakage detection system based on the mixed interferometer principle of Mach-Zehnder (M-Z) and Sagnac is introduced. The working principle of the system and method for locating leaks are described. Experiments are performed in air and underwater environments. Experiments are carried out at 4025 m, 7043 m and 9050 m from the leakage position to the Faraday rotator mirror. The experiments test the impact of different environments and different leakage positions to the detection system. The experiments are carried out at 7043 m from the leakage position to Faraday rotator mirror and repeated 20 times to test the accuracy of detection system. The results show that in the underwater experiment, the interference signal spectrum strength is greater and band is wider. The farther of leakage points from the Faraday rotator mirror, the greater absolute error of the experimental results. The system can detect and locate the slight leakage signal of the gas pressure within the pipeline at 0.5 MPa, with leakage aperture of 2.5 mm, and average relative positioning error is 1.44%.