Refractive Index Sensing of SMS Fiber Structure Based Mach-Zehnder Interferometer

A Mach-Zehnder interferometer based on single-mode-thin-core-multimode-single-mode (STMS) fiber structure for refractive index (RI) measurement is proposed and experimentally demonstrated. It works on the basis of interference between the core mode and cladding mode. Using the multimode fiber core, the transmission spectrum of STMS structure is very sensitive to RI variations of the surrounding medium. The experimental results show that the sensor possesses a high sensitivity of 148.27 nm/RIU in the RI range of 1.333-1.403 and has a good linear response to the SRI.