Ultra-sensitive high temperature sensor based on a PMPCF tip cascaded with an ECPMF Sagnac loop

Abstract We propose a sensitivity magnified polarization maintaining photonic crystal fiber (PMPCF) Fabry-Perot probe cascaded with a Sagnac loop (SL) for high temperature measurement (up to 1000 °C). The Fabry-Perot interferometer (FPI) fabricated by fusion splicing a PMPCF tip with a single mode fiber works as a sensing interferometer. The cascaded SL consisting of a temperature insensitive elliptical core polarization maintaining fiber (ECPMF) is applied as a reference interferometer. The free spectral range of the SL is easily tailored by adjusting the ECPMF length, making it similar to that of the sensing FPI, to generate Vernier effect. Experimental results show that the temperature sensitivity of the single FPI is 13.71 pm/°C, and the sensitivities of cascaded FPI-SLs are 143.52 pm/°C, 418.7 pm/°C and 1.15 nm/°C. The measured magnification factors are about 10, 35 and 91, which are consistent with theoretical results. The linearity of temperature response is 99.94 % from room temperature to 1000 °C. The proposed ultra-sensitive sensor has promising prospects for high temperature measurement.