The sensing characteristics of microstructure-core photonic crystal fiber filled with liquid based on Sagnac interferometer

A highly-sensitive temperature sensor based on the Sagnac interferometer embedded with a microstructure-core photonic crystal fiber (PCF) has been demonstrated and studied. The PCF structure with the micro holes dis-tributed on its core is designed and the unique core is called microstructure core. All the air holes of the PCF are assumed to be filled with a temperature-sensitive liquid whose thermo-optic coefficient is much higher than that of the background material. The mode field distribution and effective refractive index are calculated based on finite element method (FEM). The influences of the structural parameter d(3) of the micro holes on the sensing characteristics are analyzed. The sensitivity of the designed PCF sensor increases as the diameter d(3) increases and the average sensitivity is up to 21.05 nm/degrees C as the temperature varies from 28.35 degrees C to 46.35 degrees C. The sensing characteristics are also discussed by just filling the air holes on the fiber cladding with the temperature sensitive liquid and removing the air holes on the microstructure core.