Research On Optical Fiber Acoustic Vibration Demodulation Method Based On Polarization Low-Coherence Interferometry And Phase-shifting Method

The optical fiber acoustic vibration sensor has the advantages of small size,high sensitivity,simple structure and anti-electromagnetic interference,the optical fiber acoustic vibration sensor has a wide range of applications and is one of the most important sensing research directions.In this paper,in order to meet the needs of high-quality demodulation of optical fiber acoustic vibration,combined with low-coherence interferometry theory and phase-shifting method,an optical fiber acoustic vibration demodulation method based on polarization low-coherence interferometry and phase-shifting method is proposed,and an optical fiber acoustic vibration demodulation system based on this method is built.The effectiveness of the system is demonstrated by test experiments.The specific works accomplished during the research are as follows:1.The excellent characteristics of optical fiber acoustic vibration sensor are introduced.The research status of optical fiber acoustic vibration sensor and demodulation method is summarized.The theory of low coherence interferometry is introduced in detail,and the phase-shifting method is emphatically analyzed.2.An optical fiber acoustic vibration demodulation method based on polarization low-coherence interferometry and phase-shifting method is proposed.Four quadrature phase-shifted signals are obtained by using four birefringence crystals with different thicknesses,and the optical fiber acoustic vibration signals can achieve high quality restoration by using four-step phase-shifting method.At the same time,the degree of influence of key parameters of the demodulation system is clarified through simulation analysis.3.The optical fiber acoustic vibration demodulation system based on polarization low-coherence interferometry and phase-shifting method is built and the experiment of stability test is carried out.The experimental results show that the stability of the optical fiber acoustic vibration demodulation system is 1.97 times and 2.63 times higher than that of the B&K calibration microphone under the 21 kHz and 40 kHz sinusoidal signals.The measurement experiment of sinusoidal displacement signal with 10 Hz and displacement of 2 ?m is carried out by the nanopositioning stage.The experimental results show that the demodulation system is effective in avoiding phase ambiguity,and not limited in the range of [-?,?],and can be applied to a larger displacement range measurement.