Juliana S. Santos

Real-time optical fibre sensor for hydro-alcoholic solutions

The fast determination of ethanol–water concentration in alcohol distillation plants is a primordial requirement to preserve the quality and reduce production losses. The present research proposes an optical fibre sensor for the measurement of hydro-alcoholic concentration in liquids based on the Fresnel reflection principle. The reflection intensities of ethanol samples with 0–100% of water content were measured at different temperatures for 1310 nm and 1550 nm wavelengths. Calibration curves were prepared by fitting the experimental data and implemented in a computer algorithm. According to the functional tests, the sensor is capable of identifying samples with less than 1% error on concentration and providing practically real-time analysis.

Analysis of immersed silica optical microfiber knot resonator and its application as a moisture sensor

An embedded silica optical microfiber knot resonator humidity sensor is presented. As silica has a poor response to environmental humidity changes, a surrounding layer of Nafion is used as a transducer. Spectral characterization and also a procedure to determine the coupling and total loss coefficients are presented. Sensitivity as high as (0.29±0.01)  nm/% relative humidity has been noticed. Possible issues that emerge from the use of Nafion such as bulk swelling, refractive index hysteresis, as well as a saturation process, are discussed.

Measurement of sucrose and ethanol concentrations in process streams and effluents of sugarcane bioethanol industry by optical fiber sensor

The measurement of process streams and effluents from sugar-ethanol industry by using optical fiber sensor based on Fresnel reflection principle is reported. Firstly, binary sucrose-water and ethanol-water solutions were measured in order to determine the calibration curves. Secondly, the co-products from various processing stages were analyzed in order to identify the sucrose or ethanol concentration. The absolute error was calculated by comparison between the nominal concentration values obtained by plant laboratory analysis and the sensor response, yielding errors ≤ 5 wt% and ≤ 5 vol% for sucrose and ethanol content, respectively. The fiber sensor provided reliable results even for samples with more complex compositions than pure sucrose or ethanol solutions, with perspectives of application on the several stages of the plant facility.

Effect of the Nanostructure Control on the Novel Optical Properties of Silica Photonic Glass Synthesized by VAD Method

This research reports the development of high homogeneity silica glass for photonic components synthesized by the VAD (Vapor-phase Axial Deposition) method. Structural radial homogeneity of silica soot were characterized by scanning electron microscopy (SEM) and small angle X-ray scattering (SAXS). It was established a relationship with the refractive index homogeneity, n, and the birefringence of consolidated boules characterized through interferometry, optical spectrometry, and polarization spectrophotometry. By controlling the silica soot nanostructure during the deposition stage, a material with high radial homogeneity of refractive index of 1 ppm and birefringence of 2 nm/cm can be synthesized.

SAXS study of optically homogeneous silica glass synthesized by flame aerosol method

Aiming the development of optically homogeneous silica glass for use on photonic components, in this research, silica boules were synthesized by the VAD (Vapor‐phase Axial Deposition) flame aerosol method by varying the H2/O2 ratio. Radial structure of sintered silica samples were characterized by small‐angle X‐ray scattering technique in correlation with its optical properties, refractive index radial homogeneity and birefringence. The refractive index was determined by interferometry and optical spectrometry. The polarization spectrophotometry was used to obtain the birefringence. The structural radial homogeneity in sintered silica glass presents strong correlation with optical properties. Also, silica glass with high radial homogeneity of refractive index of 1 ppm and birefringence of 2 nm/cm can be synthesized by controlling the H2/O2 ratio during the VAD synthesis process.