Torsion sensing characteristics of a highly birefringent photonic crystal fiber with two asymmetric cores in the Sagnac loop

Abstract

We experimentally demonstrated torsion sensing characteristics of a highly-birefringent asymmetric two-core photonic crystal fiber (HB-ATCPCF) in the Sagnac loop configuration. Two cores in the HB-ATCPCF exhibit distinct birefringence properties and light launched into them propagate with negligible coupling. The transmission interference spectrum of the device shows six frequency peaks in the spatial domain, which corresponds to the two Sagnac and four Mach-Zehnder interference spectra characterized by the four-beam interference model. Torsion response of the device was investigated by measuring the shift of the peak wavelength and the fringe visibility of the fiber interferences using fast Fourier transform-based spectrum-demodulation method.