ROBUST REFRACTIVE INDEX FIBER SENSOR BASED ON TWO UP-TAPERS PLACED IN DOWN-TAPER

Abstract

In this study, a novel tapered optical fiber sensor based on a Mach–Zehnder interferometer (MZI) for refractive index measurement is proposed. Our sensor is constructed with two up-tapers symmetrically placed in a down-taper single mode fiber. Although its waist diameter is as thick as 55 μm, the sensor can measure the refractive index. Simulation results demonstrate RI sensitivities of -94 nm/RIU and -125 nm/RIU at the lower and higher wavelength of the spectrum. The sensor is extremely robust, it can be easily manufactured and it can be used not only for RI but also for simultaneous strain and temperature measurements.