All-Metal Optical Fiber Accelerometer With Low Transverse Sensitivity for Seismic Monitoring

Abstract

An all-metal double metal diaphragm-based optical fiber accelerometer with low transverse sensitivity is proposed and experimentally demonstrated. The theoretical analysis is given based on the electro-mechanical theory. Finite element modal analysis shows that the proposed accelerometer has low transverse sensitivity. Calibration results show that axis responsivity is 41 dB (re: 0 dB = 1 rad/g) with a fluctuation ±2 dB in frequency bandwidth of 5-400 Hz. The transverse sensitivity is ~ 3 dB (re: 0 dB = 1 rad/g) with a fluctuation ±1.5 dB. A transverse sensitivity of about -40 dB is achieved. The fluctuation of the acceleration responsivity for the three accelerometers is within ±2.5 dB, which shows good consistency of the proposed accelerometer. The minimum phase demodulation detection accuracy of the phase-generated carrier is 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-5</sup> rad/Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> , and the minimum detectable acceleration can be 90 ng/Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> theoretically. With an all-metal structure, the proposed accelerometer is expected to improve the reliability of long-term use in harsh environment. These desirable features show that the proposed optical fiber accelerometer is promising for seismic wave monitoring in oil and gas exploration.