Multicore Fiber Bragg Gratings Array Shape Sensor Fabricated with an Auto-Alignment Femtosecond Laser Point-by-Point Technology

Distributed fiber-optic shape sensor has been a powerful tool for variety of applications, such as structural deformation, minimally invasive surgery, and micro robotics in harsh environments. Such sensor, however, are incompatible with the demand of long-distance distributed sensing or high spatial resolution measurement. By utilizing the combination of image recognition and micro-displacement compensation, we demonstrate an auto-alignment femtosecond laser point-by-point technology, that capable of inscribing fiber Bragg grating (FBG) array through protective coating in commercial seven-core fiber. Based on the proposed method, a shape sensor array consisting of 140 FBGs has been created. Implementation of this sensor array has shown a maximum bend sensitivity of 55.49 pm/m
^-1
and a maximum error per unit length of 4.51 % in shape reconstruction.