Ultrastable cascaded LiNbO3 electro-optic modulation phase interrogation technique for Fabry-Perot acoustic sensors

In this paper, we report an ultrastable lithium niobate (LiNbO3) electro-optic modulation phase interrogation technique for Fabry-Perot acoustic sensors. Leveraging the optical characteristics of three paths of birefringent crystals to engender three low -coherence interference signals derived from a solitary light source, wherein one path is composed of two LiNbO3 crystals with different lengths cascaded in series, then engendering periodic electro-optic modulation and concurrent real-time compensation of the other two orthogonal interference signals. This procedure affords the generation of two normalized quadrature signals, which are subsequently subjected to precise phase demodulation. A series of experiments have been carried out to verify the feasibility of the proposed scheme. The proposed scheme can eliminate the influences of irrelevant factors in real-time, the system has excellent linear acoustic pressure response. Specifically, when the input optical power of the system is attenuated by 60 %, or when the initial cavity length of the sensor drifts -2.544 mu m or 2.862 mu m, the system can still be correctly demodulated, and the maximum relative the demodulation errors are 2.046 % and 1.476 %, respectively. With the advantages of strong robustness, large dynamic range and low cost, this scheme has great potential in practical engineering applications.