Ultrasensitive Strain Sensor Based on V-Groove Structure Long-Period Fiber Grating

We propose and experimentally demonstrate an ultrasensitive strain sensor based on a V-groove structure long-period fiber grating (V-LPFG). The V-LPFG is fabricated by using CO2 laser to etch periodic V-groove structures on a standard single-mode fiber. Utilizing the periodic V-grooves, effectively enhancing the strain sensitivity of LPFG. The effect of different V-groove depths on the strain sensitivity of V-LPFG are discussed. The experiment results show that the sensitivity of strain is up to -229.1 pm/<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \varepsilon $ </tex-math></inline-formula>. In addition, the temperature response of the sensor is measured and the temperature sensitivity is 80.18 pm/°C. Its temperature-strain cross-sensitivity is as low as -<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.35\mu \varepsilon $ </tex-math></inline-formula>/°C. The proposed ultrasensitive strain sensor has the good potential applications in engineering health monitoring and precision measurement due to its low cost, small size, simple fabrication, and high sensitivity.