Design And Manufacture Of Optical Fiber Accelerometer

With the development of optical fiber sensing technology,various types of optical fiber sensors have been proposed,which greatly promotes the development and progress of the sensor field.Compared with electrical sensors,optical fiber sensors are small in size,high in sensitivity,strong in anti-electromagnetic interference,and easy for distributed measurement.As a very important branch of optical fiber sensors,fiber optic accelerometers have been widely used in resource survey,natural disaster warning,transportation and structural health monitoring.The development of high-performance accelerometers is of great significance for people’s lives and national defense construction.In view of the structural health monitoring requirements of large-scale infrastructure,combined with the research progress of fiber optic accelerometers,a LPFG accelerometer based on a clamped beam structure and a F-P accelerometer based on an elastic diaphragm structure are designed and fabricated respectively.LPFG accelerometer adopts the intensity demodulation method and F-P acceleration sensor adopts the phase demodulation method,and builds a cavity length demodulation system based on the signal demodulation requirements.Starting from the mechanical model of inertial sensor,this paper conducts theoretical analysis of LPFG and F-P based on coupled mode theory and multi-beam interference principle respectively.The LPFG was inscribed by the femtosecond laser point-by-point direct writing method.The sensor design was realized by combining the "double-end clamped beam-mass block" structure with the LPFG.The experimental results show that its natural frequency is 13.7Hz and can work stably within 10 Hz,with an average sensitivity of 2.78 m W/g,the maximum measurable acceleration is 0.5g and resolution is 0.0072 g.Using ceramic ferrule and single-section silicon wafer as reflective surfaces,combined with the "elastic diaphragmmass block" structure,an F-P acceleration sensor was designed and the natural frequency is above 300 Hz through simulation.An F-P cavity-length demodulation system is designed based on the Fourier transform method,and the resolution of the demodulation system is 0.0561μm after the frequency domain interpolation processing.The experiment found that the sensitivity was 7.318μm/g and the resolution is 0.048 g under the 7Hz state.The frequency working range and acceleration resolution of the two sensors designed in this paper basically reach the design goals,and the natural frequency is adjustable,but the working bandwidth and sensitivity of the acceleration sensor are mutually restricted,the parameters should be determined according to the actual needs when using.In addition,increasing the speed and resolution of the demodulation system sensor can further improve the performance of the sensor.79 figures,7tables,84 references...