Curvature and Temperature Sensor Based on Anti-resonant Effect Combined with Multimode Interference

An inline fiber sensor for simultaneous measurement of curvature and temperature based on anti-resonant (AR) effect combined with multimode interference (MMI) is proposed and experimentally demonstrated. The sensing structure is simply formed by embedding a section of multimode fiber (MMF) and glass capillary between single-mode fibers (SMF). Thence the multimode interference (MMI) pattern with dips and the AR effect spectrum with the loss valleys at the resonance wavelengths can be observed on the optical spectrum analyzer (OSA). A curvature sensitivity of −9.25 dB/ $\text{m}^{-1}$ with almost unchanged wavelength can be achieved by intensity demodulation at an AR valley. And a temperature sensitivity of 30 pm/°C with a tiny intensity sensitivity −0.079 dB/°C is obtained by wavelength demodulation at a MMI dip. Different demodulation mechanisms enable our sensors to discriminate curvature and temperature. Moreover, the advantages such as repeatability of fabrication, robust structure and cost-effectiveness, further benefit its practical sensing applications.