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

•This paper presents an ultrastable technique for LiNbO3 electro-optic modulation phase interrogation in Fabry-Perot acoustic sensors.•The method utilizes the optical properties of three birefringent crystal paths, generating three low-coherence interference signals from a single 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.•A series of experiments verifies the feasibility of this scheme, showcasing its capability to eliminate real-time irrelevant factors and exhibit an excellent linear acoustic pressure response.•The proposed scheme demonstrates robustness in practical engineering applications: even with a 60 % attenuation in the input optical power or when the initial sensor cavity length drifts by −2.544 μm or 2.862 μm, correct demodulation is maintained, with maximum relative demodulation errors of 2.046 % and 1.476 %, respectively.