High-sensitivity strain sensor based on a helical-core long-period fiber grating

A highly sensitive strain sensor based on a helical-core long-period fiber grating (HC-LPFG) is proposed and experimentally investigated. The helical core is fabricated in the common single-mode fiber by using a high-frequency CO2 laser and hydrogen-oxygen flame. This helical shape core of the structure experienced the highly centralized refractive index modulation, which enhances the strain sensitivity and shortens the length of the sensing area to 2 mm. Experimental results indicate that the maximum strain sensitivity of the HC-LPFG reaches -97 pm/µɛ within the measuring range of 0-400 µɛ.