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 optical fiber ultrasonic testing technology based on M_Z (Mach_Zehnder) interferometer and a U-shaped optical fiber sensor are proposed. The interaction between optical fiber sensor and ultrasonic wave is discussed. The relationship between the sensitivity of the sensor and the effective length of the sensing fiber and the number of U-shaped structures is theoretically analyzed. The experimental results are in good agreement with the theoretical analysis. By comparing the output voltage of the detector under three different incident modes, it can be seen that the optical fiber sensor of the structure has the strongest signal detected by the detector when the acoustic signal is incident perpendicularly, that is, the sensor has strong directivity and is suitable for Surface acoustic wave orientation detection.