When detecting vibration with a phase sensitive optical time domain reflectometer, if the incident laser power is high, the photo detector might be saturated so that the front end of optical fiber become insensitive to vibration sensing; if the laser power is relatively low, long-distance detection might be impossible. In order to solve this problem, a new type of sensor structure was used to conduct theoretical analysis and experimental verification. According to the incident of high or low power, optical fiber was segmented and detected. Through corresponding data processing, the whole process sensitivity of optical fiber vibration was realized. At the same time, in order to further improve the vibration sensitivity and signal-to-noise ratio of the system, the results of avalanche diode detection and low noise photodiode detection were compared and analyzed. The experimental results of acoustooptic modulator and semiconductor optical amplifier were compared. The results show that, when the measuring distance is 38km, compared with avalanche diode detection, the use of low noise photodiodes and erbium-doped fiber amplifiers has a higher signal-to-noise ratio. Compared with acoustooptic modulators, a higher signal-to-noise ratio can be obtained by using semiconductor optical amplifiers. The new sensing structure provides a good reference for scientific research and engineering application in the field of optical fiber sensors.