Study On FBG Vibration Sensor

With the development of information technology, the monitoring on a variety of engineering structures, mechanical structures and natural disasters such as earthquake become more highly dependent on the analysis and solution of complex vibration. Traditional mechanical and electrical vibration sensors in the aspects of sensitivity, accuracy, dynamic range, anti-electromagnetic interference and so on, can no longer meet the application requirements. Fiber Bragg Grating Vibration Sensors technology can achieve an absolute measurement of physical quantities through the modulation of sensor signal's wavelength. The technology becomes a hot point in the sensor technology research field, for its advantages such as perfect capability of anti-electromagnetic interference, convenient conjugation with the WDM technology. Moreover. the equipment has light weight and small size.The FBG vibration sensor technology is studied theoretically and experimentally in this article. We design a FBG vibration sensor which has special structure of metal three-legged stand and elastic cantilever. Particularly, its natural frequency is 101.5Hz, the sensitivity coefficient is 28.5pm/m·s-2. The wavelength demodulation is achieved, whose precision is 1pm, via adopting the technology of bulk grating and linear dimensional sensitization array. The main research results are as following:1. The optical transmission characteristics of FBG is studied based on the study of the mechanism of fiber Bragg gratings and the refractive index distribution. Furthermore, temperature, axial pressure, lateral pressure on the impact of FBG and FBG's temperature and pressure of cross-sensitivity characteristics.2. The cantilever mechanical properties of uniform section and equal strength are researched in the perspective of the mechanical vibration. It should be stressed that a mechanical model of the vibration sensors is established here.Having studied the amplitude and phase frequency characteristic curves, structural parameters including the best natural frequency and damping ratio are presented.3. We have designed a micro-deflection control tester, precision amplifying circuitr and 8-bit data collecting card, Data Handling Program and resistance strain sensor which can measure the vibration of large amplitude.4. A distinctive grating paste process is performed in this paper. We make the fiber optic micro-pull control platform and 12.2Hz low-frequency vibration platform for the FBG vibration sensor. Excitingly, much better results are get under the sinusoidal excitation. With displacement sensor experiment, we discover that the accuracy of the FBG sensor is much higher than the resistance strain sensor. Finally. we created an operable three-dimensional vibration sensor model, which can be proved theoretically.