Dual-parameter optical fiber sensor based on few-mode fiber and spherical structure

An optical fiber sensor based on few-mode fiber and spherical structure is proposed and demonstrated. Temperature and refractive index can be measured simultaneously, since the interference spectrums between certain high core mode and different order cladding modes of the few-mode fiber have different sensitivities for the two parameters. The dips at 1526.4 nm and 1553.77 nm are chosen to measure the temperature and refractive index. The results of the experiment indicate that the temperature sensitivities of the dips are 0.059 nm/°C and 0.05 nm/°C, respectively. The refractive index sensitivities of the dips are −39.15 nm/RIU and −48.82 nm/RIU, respectively. And the temperature and the refractive index resolutions of the sensor are 0.95 °C and 0.0012RIU, respectively. Simultaneous measurement of temperature and refractive index can be realized by the sensor structure. This fiber interferometer sensor can also be applied in other sensing fields and has good prospects.