Estudo e desenvolvimento de sensores interferométricos de fibras ópticas com nanopartículas de ferrita de cobalto como elemento sensor

Abstract

In this work, a current and magnetic field sensor was proposed and experimentally demonstrated, using a fiber optic Mach-Zehnder interferometer (MZI) structure, where one of the interferometer arms is coated with magnetic nanoparticles. The MZI consists of a laser source that emits an optical signal, where it is divided by a coupler into two signals that are propagated by a reference fiber and a sensor fiber, which is surrounded by cobalt ferrite (CoFe2O4) . CoFe2O4, when placed in the presence of a magnetic field, causes a vibration in the fiber, altering the sensor’s transmission, causing an imbalance between the optical signals of the interferometer arms, where it is possible to analyze the sensor’s performance by parameters of sensitivity, precision and saturation. These nanoparticles were produced by the protein sol-gel method, obtaining an average crystallite size of 8, 27 and 67 nm. For a better performance analysis, samples were characterized by X-ray fluorescence, X-ray diffraction, VSM magnetic measurements and Mössbauer spectroscopy. The sensor presented a linear performance in all points of the samples in the regions between 0 to 15 mT with an output power value of approximately 20 dBm related to the output power and the applied magnetic field that can also be obtained the sensitivity that it presented 0,92, 0,74 and 1,12 dB/mT. Studies in the literature have shown the relationship between the horizontal width of the hysteresis loop and the saturation of the sensor composed of the same application of this research, however, in this work a different coating was applied, which complemented with more results that reports that the maximum applied field in the If the sensor is smaller than the width of the hysteresis cycle, the sensor tends not to saturate.