A highly sensitive Mach-Zehnder interferometric refractive index sensor based on core-offset single mode fiber

A highly sensitive refractive index (RI) sensor based on all-fiber Mach-Zehnder interferometer (MZI) was simulated and demonstrated. It was fabricated by splicing a section of single mode fiber (SMF) between two SMFs with a slight core offset at two splicing joints, which were used to excite cladding modes and couple the core mode to cladding modes. And then the interference between the core and cladding modes was utilized to measure sounding RI and the sensitivity of the sensor was enhanced by tapering fiber. Experimental results showed that the measured RI sensitivity could be up to 78.7 nm/RIU in the range of 1.333-1.374. Meanwhile, the sensor has the advantages of simple structure, small size, high sensitivity and low cost.