A novel bend-insensitive long-period fiber grating sensor

A novel bend-insensitive LPFG sensor written by high-frequency CO2 laser pulses is demonstrated, for the first time, to our knowledge. Experiment results shows that the bend-sensitivity of the novel LPFG depends strongly on curved orientation. The resonant wavelength shifted merely -0. 018 nm even for a curvature of 1.1 m(-1) at the most bend-insensitive position. Such a bend-insensitive sensor could be used to solve the problem of cross-sensitivity between bend and other measurands, such as temperature, strain or refractive index, which is an unsolved problem for LPFG sensors in practice. In addition, the bend sensitivity of the LPFG can be adjusted by selecting its circular positions.