A Compact Vector Curvature Sensor Based on a Dual-Path Mach–Zehnder Interferometer Structure

We first propose and demonstrate a compact and high sensitivity vector curvature sensor based on a dual-path Mach-Zehnder interferometer (MZI) structure with intensity-modulated operation. The sensor is fabricated via electric-arc splicing technology using two parallel optical paths, where the reference path is composed of a single-mode fiber (SMF) while the sensing path incorporates the SMF with a core-offset fiber structure. The asymmetric arrangement of the dual-path MZI, combined with the core-offset fiber design, creates a direction-dependent curvature sensitivity characteristic. Experimental results demonstrate that the proposed sensor can distinguish four directions: 0°, 90°, 180°, and 270°. For the bending direction of 180°, a peak sensitivity of −105.54 dB/m-1is achieved over the range of 0 to 0.041796 m⁻¹, which is the highest sensitivity for intensity-modulated vector curvature sensors to our knowledge. Additionally, we conduct experiments on temperature and strain. The experiments show that the proposed sensor exhibits temperature and strain sensitivities of 86 pm/°C and 4.3 pm/με, respectively, within the ranges of 30 °C–90 °C and 240–860 με. The cross-sensitivity issues of these parameters can be effectively addressed by a sensitivity matrix. The dual-path MZI structure, designed for vector detection, illuminates vision for developing sensors with various vector characteristics.