Highly sensitive liquid-sealed multimode fiber interferometric temperature sensor

A highly sensitive optical fiber temperature sensor based on liquid-sealed coreless multimode fiber (also called no core fiber, NCF) interferometer is proposed and experimentally demonstrated. By inserting the interferometer into a liquid-sealed capillary, a simple and highly sensitive fiber temperature sensor can be implemented. Owing to the high thermo-optic coefficient of the liquid and thermal expansion of the sealant, the interferometric spectra of the proposed sensor are shifting obviously with the variation of temperature; temperature response of the sensor can be effectively modulated through this way. Experimental results show that the sensitivity of the temperature sensor can be improved by tuning the refractive index (RI) value of the sealed liquid; a maximum value of 5.15 nm/°C has been obtained when the RI value of the sealed liquid is 1.450, it is close to the RI of the NCF.