Temperature-Insensitive Two-Dimensional Vector Bending Sensor Based on Fabry-Pérot Interferometer Incorporating a Seven-Core Fiber

We proposed and experimentally demonstrated a temperature-insensitive two-dimensional (2D) vector bending sensor on the basis of Fabry-Pérot Interferometer (FPI). The sensor is fabricated by splicing a section of silica capillary optical fiber (COF) between a trench-assisted seven-core fiber (SCF) and a multimode fiber (MMF). For orientation angle from 0° to 360°, the vector bending responses of six outer-core FPIs were studied at a step of 30°. From experimental results, the proposed sensor exhibits strong bending-direction dependence, and the maximum sensitivity is 200.6 pm/m
⁻¹
. The curvature magnitude and orientation angle can be reconstructed through the dip wavelength shifts of any two off-diagonal outer-core FPIs. Hence, there are 12 various combinations from six outer-core FPIs, and the average value can be taken in multiple reconstructions to develop exact 2D vector bending measurement. For curvature magnitude and orientation angle reconstructed, the average relative error is 6.2% and 3.3%, respectively. In addition, experiments verified the proposed sensor is insensitive to ambient temperature changes.