All-fiber temperature and refractive index sensor based on a cascaded tilted Bragg grating and a Bragg grating

An all-fiber dual-parameter sensor based on a cascaded tilted grating and a Bragg grating for temperature and refractive index measurement is proposed. Both fiber Bragg gratings and tilted Bragg gratings are sensitive to temperature, but fiber Bragg gratings are not sensitive to the refractive index. Therefore, through decoupling the cross sensitivity of the temperature and refractive index, the sensor sensitivity matrix can be obtained. In the temperature range of 25°C–300°C, the temperature sensitivities are 11.60 pm/°C for the fiber Bragg grating and 11.25 pm/°C for the tilted Bragg grating. NaCl solutions with concentrations from 5% to 20% are used for the refractive index test, and the refractive index sensitivity is 0.833 nm/RIU for the tilted Bragg grating. The proposed sensor can be used for dual-parameter measurement, showing good application prospects and research reference value.