Abstract
In this paper, we propose and demonstrate the optical fiber Fabry-Perot (F-P) interferometer based on birefringent crystals and polarization technology. For recovering the variation signals, the orthogonal signals are obtained based on the birefringent crystal characteristics and the proposal thickness difference between the two crystals. The differential cross multiplication (DCM) algorithm is utilized to demodulate the orthogonal signals to obtain the phase variation of the optical fiber F-P sensor. The proposed interferometer has a minimum detection phase of 0.014 $\text{rad}/\sqrt {\text{Hz}} $ at the frequency of 25 kHz. In the experiment, two kinds of vibration signals with frequencies of 25 kHz and 15 kHz are used and the proposed interferometer SNR is 70 dB and 75 dB under the corresponding reference environment respectively. The experiment results show that the proposed interferometer can realize the measurement of large dynamic signals and has high stability. The proposed interferometer has the advantages of fast demodulation and good environmental adaptability.
Highlights
Acoustic vibration detection is an important method for structural health monitoring [1], [2], acoustic imaging [3] and defect characterization detection [4], [5]
In this paper, we propose and demonstrate the optical fiber Fabry-Perot (F-P) interferometer based on birefringent crystals and polarization technology
We proposed an interferometer based on two birefringent crystals with different thicknesses, instead of dual-wavelength monochromatic light sources, to generate the orthogonal phase and demodulate the signals by the differential cross multiplication (DCM) algorithm
Summary
Acoustic vibration detection is an important method for structural health monitoring [1], [2], acoustic imaging [3] and defect characterization detection [4], [5]. The PGC method needs complicated carrier modulation, which limits the demodulation speed of high frequency signals. The demodulation speed is usually limited by the complicated demodulation algorithm Both of the PGC method and the white light interferometry are difficult to realize the demodulation of the high frequency acoustic signal. The dual-wavelength phase demodulation method requires high accurate wavelength of the two light sources, the minor wavelength drift will affect the orthogonality of the backreflected signals and lead to error of the demodulation results. We proposed an interferometer based on two birefringent crystals with different thicknesses, instead of dual-wavelength monochromatic light sources, to generate the orthogonal phase and demodulate the signals by the DCM algorithm. The experiment has demonstrated that the proposed interferometer has a large measurement range and works effectively under high frequency acoustic signals of 25 kHz and 15 kHz
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