提出了一种基于M－Z(Mach－Zehnder)干涉仪原理的光纤超声检测技术和U形结构的光纤传感器。讨论了光纤传感器与超声波之间的相互作用关系。对传感器的灵敏度与传感光纤的有效长度、U形结构的个数之间的关系进行了理论分析，实验结果和理论分析结果是一致的。通过比较超声波在三种不同入射方式下探测器的输出电压可知，该结构的光纤传感器在声信号垂直入射时由探测器探测到的信号最强，即传感器有很强的方向性，适合于对声表面波的定向检测。

An ultrasonic measuring technology using optical fiber based on M-Z(Mach-Zehnder) interferometer and a U type configuration optical fiber sensor is introduced. The interaction between the ultrasonic wave and optical fiber sensor is discussed. The theoretical analysis of optical fiber sensor sensitivity relying on the effective length of sensing fiber and number of U type optical fiber is given. Experimental results are in accord with theoretical analysis of sensitivity. Comparing output voltage of photodetector under three different incidence manners,the signal detected by this sensor is strongest when vertical incidence via experiment. So this sensor is fit for beamed monitoring of acoustic wave.