Low-temperature crosstalk and surrounding refractive index insensitive vector bending sensor based on hole-assistant dual-core fiber.

A low-temperature crosstalk and surrounding refractive index insensitive vector bending sensor based on resonance coupling 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. The transmission characteristics of the sensor are theoretically analyzed by combining coupled-mode theory and full-vector finite-element method. The bending responses of the sensor are experimentally measured in the curvature range of 0-3.6651  m. The bending sensitivities are -15.95  nm/m and 14.87  nm/m at 0° and 180° bending orientation, respectively, which are higher than that of most long-period fiber-grating-based and interferometer-based vector bending sensors. Moreover, the temperature and surrounding refractive index responses of the sensor are investigated. The measured results show that the proposed sensor has a low temperature sensitivity of 21.7 pm/°C in the range of 15°C-55°C and is insensitive to the surrounding refractive index in the range of 1.335-1.425, which reduces the cross-sensitivity from temperature and surrounding refractive index.