局部放电超声检测是发现变压器潜伏性缺陷的重要手段，但由于现有超声压电传感器自身限制，其灵敏度提升潜能极小。与之相比，光纤传感器可内置于变压器中进行超声传感测量，容易发现微小缺陷。但是，需要多根光纤引入变压器实现分布式测量及灵敏度低是现有光纤超声传感的两大障碍。本课题拟探索πFBGs（π相移光纤光栅）二氧化碳激光制备参数与其超声本征敏感度间的量化关系，提升光栅超声本征灵敏度；掌握增敏结构材料特性及尺寸参数对超声感知灵敏度及频带的影响，构建高灵敏度πFBGs增敏理论体系及方法；研究窄带光信号产生方法，互相关波长自适应调控措施及波分复用方法，建立温度自适应补偿πFBGs单光纤高频分布式超声解调光路拓扑；探索传感器超声感知范围影响因素及高温高压环境下长期稳定性，掌握大检测范围、灵敏度高、长期稳定、仅引入单根光纤的变压器局部放电光纤检测方法。

Ultrasonic partial discharge detection is an important method to locate power transformer defeats, but the sensitivity of the method is hardly to be improved limited by the traditional PZT sensor. On the contrary to the PZT, optical fiber grating sensors are suitable for the partial discharge detection in a power transformer. The bottleneck of the optical fiber ultrasonic sensors are lower sensitivity and distribution detection with multiple fibers. In the project, the πFBGs fabrication method based on CO2 laser will be investigated, and the sensitive enhancement method to improve the partial discharge detection will be studied either. Then, multiple narrow linewidth lasers generated circuit and wavelength division multiplexing will be investigated for distributed πFBGs ultrasonic sensing with only one fiber. After that, the research on laser wavelength auto adjust algorithm based on cross-correlation will be carried out to eliminate the temperature influence and improve the SNR of the proposed system. Moreover, the installed method of the proposed system into the power transformer will be examined. The detection range and aging properties under high voltage and high temperature will be gained based on theories and experiments. With the studies mentioned before, a wide detection range, High sensitivity, high reliability power transformer partial discharge detection system with only one fiber will be achieved.