Highly Sensitive Optical Fiber Sensor for Magnetic Field and Temperature Based on FPI-SPR Collaboration

A dual-parameter fiber-optic sensor achieving synchronous detection of magnetic field strength and ambient temperature was engineered through synergistic coupling between surface plasmon resonance (SPR) and Fabry-Perot (FP) interferometric mechanisms. The sensor structure mainly consists of SPR and FP for the magnetic field and temperature, respectively. Two multimode optical fibers fixed inside a hollow core fiber form an FP interference for temperature detection, while SPR forms based on a single mode fiber spliced with the output multimode optical fiber coated with Au thin-film. A layer of magnetic fluid is covered on the structure of SPR for magnetic field sensing. Experimental results demonstrate that the sensor achieves a peak magnetic sensitivity of 0.428 nm/Gs (R² = 0.992) and a thermal sensitivity of −1.000 nm/°C (R² = 0.994), respectively, within magnetic field intensities spanning 90.8 Gs ∼241.4 Gs and temperatures between 5 °C ∼50 °C. The proposed sensor achieves high sensitivity and wide measurement range of magnetic field and temperature. Moreover, the sensor features a straightforward structure and a convenient plug-and-use property, offering novel method for the combination and downsizing of multi-parameter measuring sensors in complex environments.