Compact Vector Bending Sensor Based on Hole-Assisted Optical Fiber

A highly sensitive, compact and robust vector bending sensor based on in-fiber directional coupler is proposed and experimentally demonstrated. The sensor is constructed by directly sandwich-splicing a segment of single eccentric hole-assisted dual-core fiber between two single mode fibers (SMFs). The bending responses of the sensor are experimentally measured in the curvature range of
$\mathbf{0-4.8248}\mathbf{m}^{-\mathbf{1}}$
. The bending sensitivities are
$-\mathbf{13.83}\ \mathbf{nm}/\mathbf{m}^{-\mathbf{1}}$
and
$\mathbf{15.48}\ \mathbf{nm}/\mathbf{m}^{-\mathbf{1}}$
at 0° and 180° bending direction. Furthermore, a two-dimensional vector bending sensor based on hole-assisted three-core fiber coupler is demonstrated. Two completely discrete resonance dips are observed in the transmission spectrum. The bending response of the proposed sensor is investigated at 360° range with a step of 45°. The bending curvature and direction can be identified by interrogating the wavelengths of the two resonance dips, and the maximum curvature sensitivity of
$-\mathbf{50.62}\ \mathbf{nm}/\mathbf{m}^{-\mathbf{1}}$
is achieved at 0° direction.