A High Resolution and Large Measurement Range Strain Sensor Based on Sagnac Loop and Fiber Bragg Grating in Dual-Wavelength Erbium-Doped Fiber Laser

The high-resolution strain detection holds significant research value in terms of providing early warning for cracks in aircraft, wind energy blades, and combustible gas containers. We propose and experimentally demonstrate a strain sensor based on Sagnac loop and Fiber Bragg grating (FBG) in dual-wavelength erbium-doped fiber laser (EDFL), showing the properties of high resolution and wide detection range, the polarization maintaining fiber (PMF) in the Sagnac loop serves as both an interference filter and a sensing probe. Nonetheless, the strain measurement range is limited by the Sagnac loop's short free spectral range, we add an FBG in the Sagnac loop, which provides a calibration element to improve the range. We successfully improve the spectral quality factor to 170.56 and reach a high resolution of 0.067 nm in a wide measurement range of 0-6434.81 µϵ. The results of our experiments show that the method is ideally suited for precise strain measurement, with major potential applications in environmental monitoring, health monitoring, biomedicine, and aerospace.