Optimization of cascaded fiber tapered Mach-Zehnder interferometer and refractive index sensing technology

A novel refractive index sensor with high sensitivity based on Mach-Zehnder interferometer formed by cascaded two single-mode fiber tapers was proposed and experimentally demonstrated. The dip of the measured spectrum signal caused by Mach-Zehnder interference shifted obviously when the surrounding refractive index changed. The approximate linear relationship between surrounding refractive index and spectrum dip wavelength shift was obtained experimentally. The measurement sensitivity up to 158.4 nm/RIU was showed with the surrounding RI ranged from 1.33 to 1.3792, which meant the measurement resolution about 6.3 × 10−6 could be implemented if wavelength shift measurement resolution of the optical spectrum analyzer is 1 pm. Meanwhile, its ease of fabrication makes itself a low-cost alternative to existing sensing applications.