Etched fiber bragg gratings sensors for water-ethanol mixtures: a comparative study

Abstract

Abstract-In this work is evaluated the performance of etched fiber Bragg gratings, assembled in different configurations to operate as a refractometric sensor, in the analysis of water-ethanol mixtures. Two fiber Bragg gratings operating close to 1300 nm and 1500 nm were wet-etched and employed in the sensor design. Four configurations for the refractometric sensor were studied, in dualwavelength and single-wavelength operation modes, and at two sample temperatures. Calibration curves were determined for the range between 0.0 and 100.0 % v/v of water in ethanol, and the sensor performance for each configuration was analyzed by comparing its sensitivity, conformity, repeatability and combined uncertainty. The best results showed that the sensor can be used to measure the ethanol-water concentration with combined uncertainty of 2. I. INTRODUCTION The ethanol is a substance miscible in both non-polar substances as hydrocarbons and polar substances as water. This characteristic makes the ethanol a versatile solvent used in several industrial sectors such as chemical, pharmaceutical, beverage and fuel. Particularly in the fuel sector, due to the inevitable depletion of the world's petroleum supply, there is an increasing worldwide interest in alternative, non-petroleum-based sources of energy.The ethanol production process is characterized by sequential procedures, and in several cases for which water is a constituent of the final product, the water-ethanol proportion must be periodically monitored and compared to standardized conditions to preserve the product quality. In Brazil, the ethanol used as fuel is obtained by the fermentation of sucrose. In the production process, sulfuric acid is employed to hydrolyze the carbohydrate and after the hydrolysis, the acid is separated from the sugar which is fermented to obtain the ethanol [1]. A careful monitoring of water content in ethanol is fundamental for the product commercialization as the product cost and destination are specified as a with spectral parameters of λ c1500 = 1539.87 nm and R 1500 = 22 dB, was written by using a phase mask with pitch of 1062.5 nm. B. FBG EtchingFBGs have been extensively used as temperature and strain transducers, with typical sensitivities of 13.7 pm/ºC and 12.0 pm/µε, respectively [11]. However, FBGs are intrinsically insensitive to surrounding medium refractive index once the light coupling takes place only between well-bound core modes, which are shielded from the influence of the surrounding medium refractive index by the fiber cladding. To make the FBG sensitive to changes in the surrounding refractive index, the cladding radius around the grating region must be reduced, allowing the effective refractive index of the fiber core to be significantly affected by the refractive index of external medium [12].The change in the Bragg wavelength δλ B associated with the chemical etching is given by [13]:(1) where Λ is the grating period, η po is the fraction of the total power of the unperturbed mode that flows in the etched region an...

Detection of Ethanol Concentration using a Generic Optical Sensor Platform

“…the refractive index. Experimental measurements previously reported in the literature show that the relationship between the refractive index and the concentration of ethanol in water is not linear throughout the concentration [1][2][3][4][5]. However, there is a convenient region where the refractive index behaves linearly with respect to the ethanol volumetric concentration.…”

Optical sensing of low ethanol concentration via absorption rate in visible wavelength

“…Previously, most of the ethanol optical sensor detections are in the near infrared (NIR) [4], [5] and UV regions. This paper presents the optical measurement of ethanol concentration in the visible wavelength region.…”

CO2 sensing at room temperature using carbon nanotubes coated core fiber Bragg grating

“…where n eff is the effective refractive index of the core and is the grating periodicity. FBGs have been used to sense temperature, 14 strain, 15 load, 16 refractive index, 17,18 micro fluidic refractive index, 19 humidity, [20][21][22] and also gases such as hydrogen 23 and ammonia. 24 In strain or temperature sensing, the grating periodicity and/or the effective refractive index changes with strain/temperature, causing a shift in the Bragg wavelength.…”

“…By etching the clad and core, FBG sensors can also be made sensitive to optical phase changes on the interface between the fiber core and the surrounding medium. 17,18 By controlling the etch depth, one can control the interaction of the propagating optical field with the bulk medium and 0034-6748/2013/84(6)/065002/7/$30.00 © 2013 AIP Publishing LLC 84, 065002-1 restrict the interaction with the surface to probe phenomena such as surface binding of molecular species or conformational changes in molecular layers immobilized on the surface of the fiber core.…”