Experimental and Technical Research on Fiber Bragg Grating Vibration Measuring Based on Two Matching Gratings Demodulation

The analysis of a novel demodulation technique for Fiber Bragg Grating (FBG) vibration sensors based on two parallel matching gratings has been carried out both theoretically and experimentally. The lineally model between transformed formula of optical power and the central reflection wavelength of sensing grating has been obtained. In addition, the FBG vibration sensor based upon cantilever with equalized strength is designed and the natural frequency of sensor has been obtained by calculations. The vibration experiment have been carried out to verify the feasibility of the modulation approach and the performance of the sensor, the results show that frequency measured by the FBG vibration sensor is agreement with the setting value. Moreover, the experiment also indicate that the sensor have a excellent frequency response at the measuring range of 0 similar to 30Hz, and the demodulation technique with two parallel matching gratings work well in the vibration sensing system.