Abstract
To achieve high-sensitivity and high-precision strain measurement, this paper proposes a strain sensor based on digital signal processing (DSP) demodulation of the second-order Vernier effect. The sensor consists of a Solc-Sagnac interferometer and a Sagnac interferometer connected in parallel, which generates a second-order Vernier effect and significantly enhances the sensitivity of the sensor. Furthermore, the DSP method is employed to process the complex transmission spectrum generated by the sensor, extracting and demodulating the characteristic envelope signal of the second-order Vernier effect. This enables high-precision tracking of the dip position, effectively improving the measurement accuracy of the system. Experimental results indicate that the strain sensitivity of the parallel-structured sensor reaches 367.9 pm/µε, with a high linear fitting coefficient of up to 0.9997. This excellent linear response validates the feasibility of the DSP-assisted demodulation. Additionally, further experiments demonstrate the sensor's outstanding repeatability and performance stability. With advantages including a simple structure, high sensitivity, low cost, and robust stability, the proposed strain sensor is highly suitable for precision strain detection scenarios.