High-Stability Polarization-Based Interrogation Method With Cross-Correlation for Optical Fiber Interferometric Acoustic Sensors

In this work, we propose and demonstrate a high-stability polarization-based interrogation method using cross-correlation for optical fiber interferometric acoustic sensing. Specifically, an extrinsic Fabry-Perot interferometric (EFPI) sensor based on polyphenylene sulfide (PPS) diaphragm is firstly used for signal detection, and then a cross-correlation interrogation system is formed with a birefringent crystal based on polarization low-coherence interference technology. Finally, the direct current (DC) component of the interference signal can be acquired in real-time with the help of the birefringent crystals block of known length. The system does not require an orthogonal relationship between the interference signals. Moreover, it can still work when the initial cavity length of the sensor drifts due to the influence of the environment. Theoretical simulations and a series of experiments have been carried out to verify the feasibility of the proposed scheme. And experimental results show that the sensor's initial cavity length shifts from 90.082 μm to 88.451 μm or 91.692 μm under 1 kHz acoustic signal, the maximum relative demodulation error is 0.4539 nm, and the signal-to-noise ratio(SNR)can reach 80 dB. Compared with the reported schemes, the proposed interrogation scheme simplifies the system configuration, and has properties of low cost, strong robustness, and high-frequency, so it has great potential in practical engineering applications.