Curvature Sensor Based on Hollow-Core Photonic Crystal Fiber Sagnac Interferometer

A fiber-optic curvature sensor based on hollowcore photonic crystal fiber (HC-PCF) Sagnac interferometer is demonstrated. The two ends of the 36 cm HC-PCF are spliced to the two arms of a 3 dB single-mode fiber coupler to form a Sagnac interferometer. The output spectra of the Sagnac interferometer under different curvatures are measured and analyzed. The results show that the wavelength shift has a linear relationship with the curvature, and the sensitivity of 0.232 nm.m is achieved in the curvature range of 0-9.9 m(-1). The temperature sensitivity is only 3.7 pm/degrees C, and the cross sensitivity to the curvature measurement is similar to 0.016 m(-1)/degrees C. This merit of low sensitivity to temperature is very useful for the curvature measurement.