2-D Medium–High Frequency Fiber Bragg Gratings Accelerometer

A 2-D fiber Bragg grating (FBGs) accelerometer is proposed and experimentally demonstrated in this paper. The accelerometer is composed of a universal flexure hinge and two FBGs in which the FBGs are vertically attached on the surface of the hinge. The sensing characteristics of the accelerometer are analyzed theoretically. The theoretical analysis results show that the proposed device has a linear response to applied acceleration and it was confirmed by the experiments. The experimental results show that the resonant frequencies of the accelerometer are 1050/1060 Hz in the x/y direction, respectively. The accelerometer has a wide frequency response from 50 to 900 Hz and a large sensitivity ~13.1/12.0 pm/G in the x/y direction, respectively. The maximum measurable acceleration reaches 200 G and the dynamic range is 80 dB. These unique characteristics make the accelerometer as an excellent candidate in various vibration signals monitoring field.

I. Introduction

Fiber sensors for vibration signal measurement have aroused wide attention in the application of structure health monitoring, oil and gas exploration, cross-hole seismic and micro-seismic fracture detection, etc. Fiber optic accelerometer based on different principle types have been proposed, such as modal interferometer [1], fiber laser accelerometers [2], polarization-interference-based fiber vibration sensor [3], Fabry-Perot accelerometer [4], Michelson interferometer [5], title fiber grating accelerometer [6], etc. Compared with other fiber optic accelerometers, FBG accelerometers are more dominant for FBG’s unique advantages of multiplexing capability, good linearity and wavelength demodulation [7]. Recently, Many achievements have been made in the research of one-dimensional acceleration sensors. A FBG accelerometer based on a compliant cylinder was proposed [8]. A flat frequency range from 30 to 300 Hz was obtained, and the corresponding sensitivity is 42.7 pm/G. Weng et al. [9] reported a FBG accelerometer composing of a flat diaphragm and a U-shaped rigid cantilever beam. Its sensitivity was up to 100 pm/G and the frequency response ranging from 10 to 120 Hz. Dai et.al. [10] proposed a medium-high frequency FBG accelerometer with integrative matrix structure. Its sensitivity is 200 pm/G and an eigen frequency larger than 3000Hz can be realized separately, but the sensitivity and natural frequency can not reach the maximum value at the same time. Zhang et al. [11] designed a flextensional FBG-based accelerometer with natural frequency of 16.7 Hz and sensitivity of 410.7 pm/G. Li et al. [12] demonstrated an FBG accelerometer by fixing the FBG on transversely moving inertial object, whose sensitivity was 0.634 nm/G and the resonant frequency was about 25 Hz. Liu et al. [13] proposed a FBG accelerometer based on diaphragm with sensitivity of 36.6 pm/G and a frequency range of 10–200 Hz.