Characteristics of chiral long-period fiber gratings written in the twisted two-mode fiber by CO_2 laser

Abstract

We demonstrated the fabrication of a chiral long-period grating (CLPG) by twisting a two-mode fiber (TMF) when a CO2 laser beam was sweeping along the fiber axis. The torsion, temperature, and surrounding refractive index characteristics of the fabricated TMF-CLPG were investigated experimentally. The fabricated TMF-CLPG has a high torsion sensitivity [0.7768 nm/(rad/m)], and can measure the twist rate and twist direction simultaneously. This kind of CLPG would have great potential applications in high-sensitivity optical sensors.