Acceleration Based On Fiber Bragg Grating Sensing Technology

The paper is mainly focus on active fiber laser sensing technology (especially distributed feedback fiber laser) for vibration measurement. The main contents include two parts are as follows:DFB fiber lasers with equivalent phase shift (EPS) are theoretically investigated and experimentally researched; fiber Bragg grating (FBG) based active accelerometer has also been studied.Active fiber sensing technology is based on the sensing principles of FBG and it take FBG fiber lasers as ultra high performances sensor elements. It is characteristic of some excellent properties such as extremely narrow bandwidth, high signal to noise ratio(SNR), compact size and simplicity. The DFB fiber laser based on EPS is studied theoretically and fabricated, the transmission properties of which are also tested. When 980nm pump light power is 55mW, the output power of DFB fiber laser is about 152μW, the threshold value is about 5mW, power conversion efficiency is 0.21% and the laser bandwidth is less than 50KHz.The vibration response of DFB fiber laser is experimentally researched based on the study on the theory of design accelerometer and principles of active sensing technology. Two novel fiber laser accelerometers with sylphon bellowss and double flexure strips structures have been proposed. The relative and absolute measurements to vibration signals are demodulated by a manual vibration detection system and an unbalanced Mach-Zehnder fiber interferometer with a 3×3 coupler. In our experimental setup, a piezoelectric vibrator is used as a reference meter. The experimental results show that fiber laser accelerometer is characteristic of higher accuracy and higher signal to noise ratio than passive FBG accelerometers or piezoelectric vibrator, and it is an excellent option for high precision and micro vibration detections.