A Vector Bending Sensor Based on a Core-Offset Long Period Fiber Grating Induced by an Arc-Discharge

Abstract

We proposed and experimentally demonstrated a vector bending sensor based on a core-offset long period fiber grating (CO-LPFG). The CO-LPFG is configured by CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> laser polishing on three mutually orthogonal planes of a single mode fiber (SMF) to different depths and then heating it by the electrical arc-discharge of a fusion splicer. The asymmetrical cladding structure leads to an uneven density distribution of the fiber in the molten state. Under the effects of releasing the residual stress and fiber surface tension, the fiber core deviates toward the polished deeper directions to form a core-offset structure in two dimensions. The experimental results demonstrate that the bending sensitivities of CO-LPFG reach 37.06 nm/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> −5.85 nm/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> -14.59 nm/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> and −12.45 nm/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> for four bending directions within the range of 1.12-2.10 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> The temperature sensitivity of CO-LPFG is 57.90 pm/°C in the range of 40-160°C.