Refractive index sensing properties of microfiber cascaded‐long‐tapers

The microfiber cascaded double‐tapers were constructed and used as a Mach–Zehnder interferometer by a two‐step fiber stretching process using a normal fiber splicer and a multifunctional fiber stretching machine. The morphological parameters, such as waist diameter and taper length were optimized by the simulation models. The refractive index sensing performance has been theoretically and experimentally demonstrated and compared. A sensitivity of 2606.39 nm/RIU of one Mach–Zehnder interferometer with microfiber double‐apers (central distance is ~1 cm) was obtained when the RI values changed from 1.3309, 1.3319, 1.3327, 1.3336, 1.3344–1.3352. This study proposed a novel way to design interesting microfiber devices, which will be a promising candidate for exploring optical fiber biosensors with compact structures.