Bending Vector Sensing Based on Arch-Shaped Long-Period Fiber Grating

A novel arch-shaped long-period fiber grating (ALPFG) is proposed and fabricated by a high-frequency CO
₂
laser on a single-mode fiber. The ALPFG is composed of a string of arch grids, which can provide stronger refractive index modulation than normal planar grids. The asymmetrical structure induced by arch grid and one-side exposure allows it to sense vector bending in two orthogonal directions. Within the curvature range from 0.5 to 2.2 m
^-1
, its bending sensitivities can reach 22.120 and -18.626 nm/m
^-1
for the two opposite directions. Its temperature recycle and force characteristics are also provided.