Compact three segmented multimode fibre modal interferometer for high sensitivity refractive-index measurement

We experimentally demonstrate a new compact surrounding refractive-index sensor using a MMF-CSF-MMF (MCM) structure. The evanescent waves in the coreless silica fibre (CSF) region can directly interact with the surrounding medium. Due to its distinctive resonant spectral feature, the MCM sensor showed a high sensitivity of 4.37 × 10 −4 for a refractive index range of 1.30 to 1.44, suggesting that the proposed device may be suitable for a wide range of biomedical and chemical sensor applications.