Fiber-optic Mach-Zehnder Interferometer for Refractive Index Measurement Based on MEMS Optofluidic Platform

Abstract

We present a fiber-optic sensing configuration based on Mach-Zehnder interferometer (MZI) embedded into the MEMS optofluidic platform for measurement of index of refraction of liquids in dynamic regime. The sensing principle is based on the low-coherence interferometry, characterized by generation of Gaussian shape interferograms, which maximum position depends on the optical path difference (OPD) between the sensing and reference arm of the MZI. When liquid flows through the central microchannel of the optofluidic platform it crosses the light beam between the two optical fibers in the sensing arm causing the OPD change. An algorithm has been applied for calculation of index of refraction of liquids out of the raw interference signals. We obtained very good agreement between the experimental results and literature data of index of refraction of subjected fluids. The accuracy of index of refraction measurement is about 1 % that is predominantly determined by accuracy of reading the position of mechanical scanner.