Dumbbell-Shaped Mach–Zehnder Interferometer With High Sensitivity of Refractive Index

We proposed and fabricated a dumbbell-shaped Mach-Zehnder interferometer (MZI) on a single mode fiber using a revised program of the fusion splicer. To the best of our knowledge, it is the first time one has produced and applied the MZI of this configuration to detect liquids refractive indexes. The dumbbell shape has a length of 1.9 mm and a minimum waist diameter of 63 μm. The wavelengths shift with the changing of surrounding refractive indexes, and the refractive index sensitivity is as high as 251 nm per refractive index unit with the linear range of 1.333-1.391 that is tens of times higher than the MZI based on two fiber tapers.