A New Spring-Shaped Long-Period Fiber Grating With High Strain Sensitivity

A new type of spring-shaped long-period fiber grating (S-S-LPFG) written with CO2 laser is proposed in this letter. A single-mode fiber is etched clockwise in four directions and any two adjacent etched regions are partially coincident in the vertical direction. The special manufacturing method makes that the S-S-LPFG has satisfactory strain sensitivity. The experimental results prove that the strain sensitivity of the S-S-LPFG is up to 30 pm/mu epsilon with the range of 0-700 mu epsilon, which is nearly 18 times higher than that of the normal CO2-laser-notched long-period fiber gratings (CO2-LPFGs). The temperature sensitivity of the S-S-LPFG is also calculated from the experimental data as 37 pm/degrees C. It is strongly believed that the S-S-LPFG could be an excellent candidate for the strain sensors.