Fiber Sagnac interferometer based on a liquid-filled photonic crystal fiber for temperature sensing

A fiber Sagnac interferometer based on the square-lattice photonic crystal fiber (PCF) for temperature sensing is designed. All the air holes are assumed to be filled with temperature sensitive liquid. The temperature sensing characteristics are analyzed by finite element method (FEM). The phase birefringence B, the group bi-refringence Bg, and the sensitivity dependence on the operable wavelength lambda are studied, and the temperature varies from 25 degrees C to 85 degrees C. The birefringence sensitive coefficient of partial derivative B/partial derivative T is -10(-7)/ degrees C. The sensitivity could reach to -11.9 nm/ degrees C (-29 750 nm/RIU) at 1.8 mu m as the temperature is 25 degrees C. The sensitivity is also studied by the transmission spectrum, and the wavelength spacing between the resonance wavelengths at 85 degrees C can reach to 492 nm. The average sensitivity could reach to -7.54 nm/degrees C (-18 850 nm/RIU). The diameter d(1) on the sensing characteristics of the temperature sensor is also analyzed. The temperature sensor shows high sensitivity and broad detecting window. (C) 2016 Elsevier B.V. All rights reserved.