Fiber optic curvature sensor

A fiber optic curvature sensor based on discrete Fiber Bragg gratings inscribed in a multi-core fiber is presented. The individual cores of the multi-core fiber are each interrogated by a custom-built spectrometer running at up to 20 kHz. They are interfaced with a custom-tapered combiner of single-core fibers fusion spliced to the multi-core fiber. The curvature and bend direction for each fiber segment is obtained from the geometric relation of strain measurements in all interrogated fiber cores, thus eliminating temperature influences and minimizing noise. In order to reconstruct the shape of the measurement fiber, both constant curvature and spline interpolation using homogeneous transformation matrices are performed and compared to given free space equilibrium state solutions for a Kirchhoff elastic rod.