Highly sensitive strain sensor based on a long-period fiber grating with chain-shaped structure

In this paper, a novel chain-shaped long-period fiber grating (CS-LPFG) for strain measurement is investigated and experimentally demonstrated. This structure is achieved by polishing periodic slant planes on a single-mode fiber with a high-frequency CO2 laser. The chain-shaped structures improved the strain sensitivity of the sensor while shortening the length of the sensing unit. Experimental results show that the strain sensitivity of CS-LPFG is 34.8 pm/µe in the range of 0–650 µe, and the total length of the sensing unit is significantly reduced to 7.5 mm. Meanwhile, the temperature-strain cross talk is 1.6 µe/°C, which is much lower than that of most fiber strain sensors.