High Resolution Force Sensor Based on Dual-Wavelength Erbium-Doped Fiber Laser Integrating a Filter of Sagnac Loop and a Fiber Bragg Grating

We propose a high resolution force sensor based on a dual-wavelength erbium-doped fiber (EDF) laser. By integrating a Sagnac interferometric loop with a fiber Bragg grating (FBG), the sensor achieves both sensing and calibration functions. In this sensor, the polarization-maintaining fiber (PMF) within the Sagnac loop serves simultaneously as an interference filter and a sensing probe. Although it offers high sensitivity, the measurement range of the sensor is limited by the narrow free spectral range (FSR) imposed by the Sagnac loop and the laser gain. To overcome this limitation, we introduce an FBG into the laser cavity to calibrate the force value when it exceeds one FSR, thereby effectively extending the operational range of the sensor. Experimental results show that the sensor achieves a high sensitivity of 14.19 nm/N with a high resolution of 0.035 N in the range of 0–4.9 N. In addition to high sensitivity and high resolution over a broad measurement range, the sensor also exhibits good stability, demonstrating promising potential for precision force analysis.