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Due to the vast area of application and reliability, fiber optic magnetic field sensors have been the subject of several studies, however, some of these application areas are submitted to temperature variations, which can hinder the sensors in monitoring the magnetic field. With this panorama, this work analyzes through computational modeling a fiber optical magnetic field sensor, using the magneto-optical Faraday effect and observing temperature effects in the sensor response. For modeling, a numerical model built in COMSOL Multiphysics is used. The results show a value for cross-sensitivity of 3.27 mT/°C in a non-optimized configuration of the sensor and of 2.47 mT/°C for an optimized configuration. A methodology for optimizing the sensor to operate in a certain temperature range, 55 to 75 °C, is also discussed. The results presented in this work show that the temperature is an important factor to be considered to improve the selectivity and to obtain the correct sensitivity of the sensor. [ABSTRACT FROM AUTHOR]

We report the development of a measurement system capable of monitoring and characterizing the main features of the leakage current flowing on a polluted insulator string of a high-voltage transmission line. The system comprises a fiber-optic sensor, directly connected to one insulator of the string, that emits a sample of the leakage current waveform to a processing module via an optical link. A capacitive sensor connected to the processing module allows recording the relative humidity of the outer environment. At the present stage, six measurement units have been deployed on CHESF's electrical transmission system in the Northeast of Brazil, and studies are underway to further correlate the degree of environmental pollution with humidity and leakage current activities on high-voltage insulator strings. Index Terms--Flashover, insulators, leakage current, optical-fiber transducers, power transmission lines.

This article presents the proposed structure and the simulation results from analytical and numerical modeling of two corrosion sensor elements in D-shaped optical fiber: one based on the lossy mode resonance (LMR) effect and the other based on the effect of surface plasmon resonance (SPR). In the first sensor element, a bilayer of titanium dioxide - aluminum (TiO2-Al) is deposited on the D-shaped region, operating in LMR conditions, while, in the second sensor element, an aluminum(Al) monolayer is deposited under D-shaped region, operating in SPR condition. The sensor elements can operate separately, enabling simultaneous twoparameter measurements at two different points, or they can operate in cascade configuration, increasing the operating range and sensitivity of the sensor set. The D-shaped region of the optical fiber is modeled with an analytical model based on the Fresnel formulation, and also with a numerical model, which uses the finite element method with the COMSOL Multiphysics 5.2 software. The transmission of light through the D-shaped region causes peculiar variations in each light polarization in each sensor element, depending on the metal thickness. Both regions are subject to a corrosive environment. The sensor elements are evaluated separately and in cascade configuration, using polarized and nonpolarized light. Finally, the obtained results show two resonance valleys for the same operating wavelength, resulting in a higher operating range with high sensitivity, compared to other corrosion sensor structures found in the literature. [ABSTRACT FROM AUTHOR]

In this paper, a new optical fiber corrosion sensor based on metallic bilayers is described. The detection region is located at a fiber end facet and we present simulations as well as experimental results in controlled lab conditions for Ti(10 nm)/Al(10 nm) and Ni(5 nm)/Al(5 nm) bilayers. We perform the characterization of the device by numerical simulations using the COMSOL Multiphysics software, and with an analytical model, which makes use of the Fresnel equations. According to the simulations, the change in the reflected optical signal over time is related to variations in the thickness of the metallic films by the corrosive process and, consequently, the corrosion rate in each metal of the bilayer can be obtained. Upon the simulation results, sensor devices were fabricated by depositing thin metallic films on the cleaved facet of the optical fiber using the sputtering method. We show that the use of a metallic bilayer as a transducer, instead of a monolayer, improves the sensor measuring interval (20 ± 1 nm) and provides information about the corrosion rate along the corrosion process. [ABSTRACT FROM AUTHOR]