The Study Of Vibration Sensor Which Is Applied To The Quasi-distributed Optical Fiber Fence System

Vibration is a widespread phenomenon, and the measurement of the vibrationsignal plays a vital role in many important areas. The vibration signal monitoring of thefiber grating is also an important research problem. Most of the sensors used in thequasi-distributed optical fiber fence system are temperature and strain sensors.Temperature sensors can sense changes in ambient temperature, in most cases they areapplied to the fire security fence alarm system. Strain sensor is sensitive to staticdeformation, and mostly used in perimeter security monitoring. However, due to thelimitations of strain sensor, such as lack of collecting information, slow deformationrecovery, propagation delay, and limited reuse distance, the sensors can’t satisfy thecomplex environment and long-distance monitoring requirements. FBG vibrationsensors are derived from the stain sensors, not only can survey the outside variation, butalso sensitive to the vibration signal. In actual project, the transmission distance of avibration signal is further than stain signal transmission distance, the deformation on thefence is generally accompanied by vibration. If strain sensor is not sensitive enough, itcan’t monitor the small deformation caused by slight vibration, but the vibration sensorcan compensate the defect.In this paper, based on the study of fiber grating sensing used in vibrationmeasurement, combined with the actual demand for the quasi-distribute fiber opticfence system, we designed a new type of horizontal mandrel type low-frequencyvibration sensor. The main contents include:1. The existing vibration sensor and the application of FBG vibration sensor arestudied, and the existing fiber grating vibration sensor which has a good applicationvalue are summarized, while the status of FBG sensor used in optic fiber fence systemare studied, and we have found many flaws in the sensor application, which show theneed to develop a new FBG vibration sensor to solve practical engineering problem.2. According to the basic principle of fiber grating applied to vibrationmeasurement and the design of several typical FBG vibration sensors, we improved thedesign of some existing sensors, which had good sensitivity and frequency response, and simulated the structure by ANSYS, verified the results of the theoretical analysis.3. A vibration sensor has been designed, which is suitable for optic fiber fencesystem, we analyzed its performance by ANSYS, compared it with server other models,and drew a conclusion that the structure has advantages in project application.4. Test apparatus is built, and the produced FBG vibration sensor is reachedexperimentally. The experimental results show that the acceleration sensitivity reaches127.4pm/g, and the amplitude sensitivity is0.16nm/mm. The natural frequency responseof the sensor reaches42Hz, and the frequency response is flat within the frequencyrange of less than30Hz. Compared with software analysis results, the experimentalresults are in the range of allowable error.5. To conduct the monitoring experiment, the packed FBG vibration sensor andthe strain sensor are applied to the quasi-distributed fiber optic fence system. Indifferent additions, the test results of these two sensors are compared, and the reasonsare analyzed. It can be concluded that FBG vibration sensor has more advantages thanstrain sensors in monitoring measurement.6. The fiber Bragg grating vibration sensor is applied to the fiber fence system.Based on the characteristics of the waveform, the pattern recognition algorithms arestudied, and the future direction of development is proposed.