Sensing characteristics of a Sagnac interferometer based on ethanol-filled photonic crystal fiber with two ultra-large holes for temperature measurement

Abstract We propose a Sagnac interferometer (SI) based on ethanol-filled photonic crystal fiber (PCF) with two ultra-large holes for temperature measurement. The phase birefringence of the fully-filled PCF varies significantly with the temperature which is realized by infiltrating ethanol into air-holes. Two ultra-large holes in y direction near the core result in a high birefringence of PCF. By selecting a fiber length of 2.5 cm, the average sensitivity of temperature can be up to -34 nm/°C with a resolution of 0.00029 °C in the wavelength range of 780 nm–2170 nm within temperature variation of 40 °C. The proposed PCF with the simple structure is easy to prepare in the experiment. Furthermore, due to the ultrahigh-sensitivity, the proposed sensor provides a new implementation for accurately temperature measurement.