Omnidirectional bending sensor based on fiber Bragg gratings inscribed in a seven-core fiber

We demonstrated a novel omnidirectional bending sensor by use of fiber Bragg gratings (FBGs) inscribed in a homogeneous seven-core fiber. The seven FBGs were simultaneously inscribed in each of all seven cores using a modified Talbot interferometer and a lens scanning method. The omnidirectional bending response of six outer-core FBGs was investigated in all 360° directions with a step size of 15°. A strong angular dependence of the curvature sensitivities was achieved radially, with a maximum sensitivity of 59.47 pm/m
^-1
. They were displayed in a polar-coordinate system with six perfect '8'-shaped patterns. The seven-core fiber-based FBGs have significant potential as compact and robust vectorial bending sensors for intelligent artificial limb applications.