Based On The Gaussian Filter Fbg Vibration Sensor Demodulation Technique

The fiber grating can be used as the sensor to get physical quantities such as temperature, stress, current, magnetic field, vibration etc by detecting the variation of reflection or transmission center wavelength. Because of the sensor advantages of high electromagnetic interference resistance and sensitivity, fine electrical insulation, good safety and reliability, resistant and easy to constitute optical fiber sensors network, the fiber grating has potential application in aerospace, navigation, oil exploration, power transmission, nuclear industry, medical science, scientific research and other fields. This thesis focuses on the demodulation technology of fiber Bragg grating sensor, the main research content and results are as follows.The reflectivity and reflection spectrum of fiber Bragg grating were analyzed by the fiber grating coupling theoretical model. Based on this, the principle and feature of fiber grating sensing in stress strain, pressure and temperature were discussed. The demodulation method and multiplexing technology of fiber Bragg grating were introduced as well.The effect of axial and radial direction force on fiber Bragg grating sensing was discussed. The experimental results of fiber grating sensing coincided with the theoretical analysis, by measuring the center wavelength of reflection spectrum of fiber Bragg grating with the interrogator.In order to overcome the shortage of dynamic measure range in traditional fiber grating demodulation, Gaussian filter with broader bandwidth was introduced to replace matching grating. After theoretical analysis, effective method to obtain work-point was discussed. The demodulation experiment was performed by replacing matching-grating (3dB,0.241nm bandwidth) with filter (3dB,0.374nm bandwidth). This system achieved effective vibration demodulation at 1000Hz and broadened the dynamic measure range from 0.29nm to 0.378nm. In addition, within this range, the sensitivity and measurement error of the system is 3.6 mv/pm and 2.7% respectively.