The Research On High Resolution Fiber-optic Inclinometer And Accelerometer Based On Fabry-Perot Interferometer

Optical fiber sensor was widely used in various fields for its multiple advantages of immunity to electromagnetic interference,resistance to harsh environment and easy to be multiplexed,for example,in the field of road and bridge safety monitoring,energy security,building state monitoring and aerospace safety,and optic fiber inclin-ometer play an important role in optical fiber sensor system.Most of fiber sensors is based on the principle of fiber Bragg grating nowadays,which is measure the tilt by the means of the characteristic wavelength's shift because of the stress when the tilt occurs.To solve the problems that the field of optical fiber tilt sensors' requires about high resolution and wide dynamic range sensors,a high resolution opical fiber tilt sensor based on F-P Interferometer was proposed in this paper,and it can also measure the vibration at the same time.The main work of this paper is summarized as follows:Based on the simple pendulum model,the measurement mechanism of inclination angle of accelerometer is theoretically analyzed,and the linear relationship between the length of F-P cavity and the inclination angle is obtained,and the acceleration measurement mechanism of inclination acceleration sensor is theoretically analyzed by using forced damped vibration model.the length of F-P cavity is not only related to acceleration,but also to external vibration frequency.To solve this problem,a non-linear fitting acceleration frequency response curve is drawn to measure the external acceleration.In this paper,a fast WLI demodulation algorithm as a phase demodulation method is employed in order to get the cavity length.On this basis,a physical model of sensor based on the principle of simple pendulum is made.Copper is used as the material of pendulum mass block,carbon fiber cable is used as the material of suspension,and aluminum is used as the material of encapsulation shell.In order to compare with the experimental results and provide reference for the experimental design,the model of optical fiber sensor is established in the large simulation software,and the modal analysis and harmonic response analysis are carried out,two natural frequencies of 0.886 Hz and 1.667 Hz are obtained in the range of 0-200 Hz.Through the inclination calibration experiment,the inclination range is determined to be-2.8-+2.6 and the inclination resolution of the sensor is measured to be 0.023?.The resonance of the sensor at 2.5Hz was measured by acceleration measurement.The acceleration frequency response curve was drawn by non-linear fitting.The external acceleration value was obtained by curve data,and the frequency range of the external vibration was determined to be 0-180 Hz.Experiments show that the sensor can measure the inclination and acceleration simultaneously and in real time.