Investigation On The Novel Accelerometer Based On The Fiber Gratings

With the rapid development of fiber communication technology and sensing technology, lots of new technology has been applied to the traditional industries. In recent years, accelerometers based on optical fiber attract many interests. Optical acceleration sensors have many advantages over conventional ones, such as immunity to electromagnetic interference, small size, light weight, large dynamic range, high sensitivity and resolution, capability of embedded into material, multiplexing and capability to transmit signals over long distance without any additional amplifiers. Various types of optical accelerometers based on the intensity modulation, phase modulation, wavelength modulation, and polarization modulation, etc., have been reported. In this dissertation, accelerometer based on the D-shaped Fiber Bragg Grating (D-FBG) and Long Period Fiber Grating (LPFG) was investigated in experiment and theoretic analysis.Due to the non-circularly symmetric configuration, bending will induce the shift of center wavelength of D-FBG Mode distribution, Birefringence effect of D-fiber was simulated and bending effect of D-FBG was analyzed in this paper. Based on D-FBG, a novel method of measuring acceleration is presented theoretically and experimentally. With the parameters of the D-shaped fiber used in the experiment, the sensitivity of the sensor can be calculated to be 611.86με/g, and the resonant frequency is 4.56Hz. The experimental data shows that the sensitivity and minimum resolution of the sensor are obtained as 563.67με/g and 1.15×10^-3g, respectively. It can be used in detecting both very low frequency and small acceleration.LPFG has high sensitivity to the bending. We fabricate LPFG by UV exposure the hydrogen loaded optical fiber. Experimental analysis has been done to the bending effect. An accelerometer using LPFG is designed. The experimental results shows that the sensitivity of the sensor based on the LPFG reaches 12.65nm/g, minimum resolution is 1.9×10^-3g, and the resonant frequency can be calculated to be 28.9 Hz, which reveals that the sensitivity of LPFG-accelerometer is as 18.48 times as that of D-FBG accelerometer. At the same time, a novel wavelength demodulation of LPFG based on the wavelength-matched FBG is proposed. It has many merits, such as low cost, simple structure, fast response, easy to multiplexing, and so on. Our results have some reference value to some engineering application.