Simple Method for the Elimination of Polarization Noise in BOTDA Using Balanced Detection and Orthogonal Probe Sidebands

Polarization noise arises in Brillouin optical timedomain analysis due to the strong polarization sensitivity of stimulated Brillouin scattering. To avoid this noise, it turns out to be indispensable to perform some kind of polarization scrambling, either in the pump pulse, the probe signal or both. This is usually achieved using polarization scrambling/switching systems, which, being mechanical, tend to be not as robust as it would be desirable. In this paper, we propose a completely passive system,with no moving parts, to eliminate polarization noise in a BOTDA. It is based on the use of passive depolarization of the pump pulse together with balanced detection among orthogonally polarized Stokes and anti-Stokes bands of the probe signal. The setup requires no alignment readjustment over time and provides a performance similar to a conventional BOTDA using scrambler.Ministerio de Economía y CompetitividadComunidad de MadridEuropean Commissio

Balanced detection in Brillouin optical time domain analysis

We propose the use of balanced detection in Brillouin Optical Time Domain Analysis (BOTDA) sensors. Balanced detection can be effectively accomplished among the Stokes and anti-Stokes bands in the probe signal. This type of detection leads to a doubling of the trace amplitude and at least a √2 increase in signal to noise ratio over the conventional configuration. Moreover, it leads to a complete cancellation of the common-mode noise in the probe signal, including relative intensity noise in Raman-assisted configurations. We show all these benefits both theoretically and experimentallyMinisterio de Ciencia e InnovaciónComunidad de MadridEuropean Commissio

Removal of azo dyes orange II and reactive black 5 from aqueous solutions by adsorption on chitosan beads modified with choline chloride: urea deep eutectic solvent and FeO

The removal of the azo dyes Orange II (OII) and Reactive Black 5 (RB5) from aqueous solutions was studied using three types of adsorbents derived from chitosan: unmodified chitosan beads (un-Ch), chitosan beads tuned with a deep eutectic solvent (DES) composed of choline chloride:urea at a 1:2 molar ratio (Ch-DES), along with FeO nanoparticles added to chitosan and modified with DES (Ch-FeO-DES). Both dyes were effectively removed in 3–4 h when Ch-DES beads were used, at a dye concentration range of 25–50 mg/L. The modification with DES improved the removal efficiency to achieve increases of around 32% for OII and 17% for RB5. The adsorbent dosage and the initial dye concentration influenced the adsorption process. Isotherm adsorption models (Langmuir, Freundlich, and Temkin) and kinetic models (pseudo-first-order, pseudo-second-order, intraparticle diffusion, and Elovich models) were applied to identify the adsorption behavior. The process could be characterized by employing the pseudo-second-order kinetic model and fitting it to the monolayer Langmuir isotherm. The adsorption occurred on a monolayer with no interaction among dye molecules when electrostatic forces would determine the attaching of dye molecules on the adsorbent. OII was efficiently desorbed by an alkaline solution, while RB5 was more strongly attached. The adsorbent could be recycled, after regeneration with an acid solution, for at least 5 reuse cycles while still achieving effective OII removal. Reactivation with a diluted EDTA solution allowed the authors to recycle RB5-attached beads, achieving optimum removal in two further uses.Xunta de Galicia | Ref. GPC-ED431B 2020/08Agencia Estatal de Investigación | Ref. PID2019-107728RB-I0

Removal of Acid Blue 80 from aqueous solutions using chitosan-based beads modified with choline chloride: urea Deep Eutectic Solvent and FeO

An alternative chitosan-based adsorbent modified by impregnation with deep eutectic solvent (DES) choline-chloride:urea at a molar ratio 1:2 proved efficient removal of the anthraquinone dye Acid Blue 80 (AB80) from aqueous solutions, and offered enhanced adsorption capacity compared to the starting materials. The adsorption was mainly affected by initial AB80 concentration, adsorbent dosage, contact time, and slightly influenced by temperature (25–45 °C), and pH (3.5–10). The pseudo-second-order kinetic model fitted the experimental data, and pseudo-first order model fitted as well at the highest AB80 concentration, 250 mg/L. The experimental data agreed with the Langmuir isotherm model, with a maximum adsorption capacity of 61.64 mg/g at 35 °C. The process was exothermic above 100 mg/L of dye and spontaneous up to 200 mg/L (T < 35 °C). The adsorbent could be reused without further treatment at least 5 times providing ≥40% removal, whereas the dye could be efficiently recovered by NaOH desorption. Electrostatic interactions as well as physisorption could explain the adsorption behaviorAgencia Estatal de Investigación | Ref. PID2019-107728RB-I00Xunta de Galicia | Ref. ED431B 2020/08Financiado para publicación en acceso aberto: Universidade de Vigo/CISU

Unexpected non-local effects in dual-probe-sideband BOTDA

Until now, non-local effects in dual-probe-sideband Brillouin Optical Time Domain Analysis (BOTDA) systems have been considered negligible if the probe power is below the Stimulated Brillouin Scattering (SBS) threshold. In this paper, we show the appearance of non-local effects even below the SBS threshold. The pump pulse experiences a frequencydependent spectral deformation that affects the readout process differently in the gain and loss configurations. The main conclusion of our study is that the measurements in gain configuration are more robust to this non-local effect than the loss configuration. These results are of particular interest for manufacturers of long-range BOTDA systems.European CommissionMinisterio de Economía y CompetitividadComunidad de Madri

Non-local effects in dual-probe-sideband Brillouin optical time domain analysis

According to recent models, non-local effects in dual-probesideband Brillouin Optical Time Domain Analysis (BOTDA) systems should be essentially negligible whenever the probe power is below the Stimulated Brillouin Scattering (SBS) threshold. This paper shows that actually there appear non-local effects in this type of systems before the SBS threshold. To explain these effects it is necessary to take into account a full spectral description of the SBS process. The pump pulse experiences a frequency-dependent spectral deformation that affects the readout process differently in the gain and loss configurations. This paper provides a simple analytical model of this phenomenon, which is validated against compelling experimental data, showing good agreement. The main conclusion of our study is that the measurements in gain configuration are more robust to this non-local effect than the loss configuration. Experimental and theoretical results show that, for a total probe wave power of ~1 mW (500 μW on each sideband), there is an up-shifting of ~1 MHz in the Brillouin Frequency Shift (BFS) retrieved from the Brillouin Loss Spectrum, whereas the BFS extracted from the measured Brillouin Gain Spectrum is up-shifted only ~0.6 MHz. These results are of particular interest for manufacturers of longrange BOTDA systems.European CommissionMinisterio de Economía y CompetitividadComunidad de MadridUniversidad de Alcal

Comparación de ecuaciones para ajustar curvas de crecimiento de vacas Holstein, Jersey y Jersey x Holstein en pastoreo

The objective of the study was to compare the goodness of fit of four nonlinear equations to describe the growth curves of Jersey, Holstein, and Jersey x Holstein cows in grazing. The Brody, Gompertz, von Bertalanffy, and Logistic equations were fitted to the data (n= 2,315) on weight and age of Jersey (n= 54), Holstein (n= 6) and Jersey x Holstein (n= 30) cows. For each animal, genotype and equation, the parameters A, b and k that generated the best-fit growth curves were estimated. In each of the four equations compared, parameter A corresponds to the upper asymptote of the curve and estimates the ‘mature weight’ of the animal, parameters b and k represent the integration constant and the maturation rate. For the growth curves of Jersey cows and Jersey x Holstein crosses, the Gompertz and von Bertalanffy equations produced the best fit. In contrast, the Logistic equation had the best fit for the growth curves of Holstein, followed closely by the Gompertz and von Bertalanffy equations. Under the management and feeding conditions of the animals in this study, the growth curves of the females of the three genotypes studied can be fitted with the von Bertalanffy equation.El objetivo del estudio fue comparar la bondad de ajuste de cuatro ecuaciones no lineales para describir las curvas de crecimiento de vacas Jersey, Holstein, y Jersey x Holstein en pastoreo. Las ecuaciones de Brody, Gompertz, von Bertalanffy, y Logística se ajustaron a los datos (n= 2,315) de peso y edad de vacas Jersey (n= 54), Holstein (n= 6) y Jersey x Holstein (n= 30). Para cada animal, genotipo y ecuación, se estimaron los parámetros A, b y k que produjeron las curvas de crecimiento de mejor ajuste. En cada una de las cuatro ecuaciones comparadas, el parámetro A corresponde a la asíntota superior de la curva y estima el ‘peso maduro’ del animal, los parámetros b y k representan la constante de integración y la tasa de maduración. Para las curvas de crecimiento de las vacas Jersey y las cruzas de Jersey x Holstein, las ecuaciones de Gompertz y de von Bertalanffy produjeron el mejor ajuste. En contraste, la ecuación Logística tuvo el mejor ajuste para las curvas de crecimiento de Holstein, seguida muy de cerca por las ecuaciones de Gompertz y von Bertalanffy. En las condiciones de manejo y alimentación de los animales en este estudio, las curvas de crecimiento de las hembras de los tres genotipos estudiados pueden ajustarse con la ecuación de von Bertalanffy

Long-range, Power-efficient Distributed Flow Measurements Using Chirped-pulse Phase-sensitive Reflectometry

The Optical Networking and Communication Conference & Exhibition,, 11/03/2018-15/03/2018, San Diego, Estados Unidos.We demonstrate a technique allowing to perform distributed wind speed measurements over >17 km with <0.6 km/h uncertainty at only 60 mW/m of power dissipation. Applications in dynamic line rating and catenary monitoring are envisaged.European CommissionMInisterio de Economía y CompetitividadComunidad de MadridUniversidad de Alcal

N- and S-doped carbons derived from polyacrylonitrile for gases separation

The CO2 capture using adsorption can reduce the carbon footprint, increasing the sustainability of the process without the production of wastes present in commonly used industrial operations. The present research work analyses the effect of the doping-agents incorporation in carbon materials upon adsorption and separation of gases, specifically for carbon dioxide and nitrogen. The carbons precursor was polyacrylonitrile (PAN), which enabled the incorporation of nitrogen atoms in the structure, whereas sulphur doping was reached using pure sulphur after the carbonisation step. The influence of several variables (such as temperature or pressure) and characteristics of synthesised materials (mainly corresponding to surface characteristics) on carbon dioxide separation has been evaluated. Adsorption isotherms were determined for each gas (CO2 and N2) at different temperatures and pressures. Different adsorption models were evaluated to fit the experimental data. In general, the Toth isotherm described better the adsorption for both gases. Important parameters such as CO2/N2 selectivity and heat of adsorption were determined using the IAS theory and the experimental isotherms at different temperatures, respectively. Non-activated carbons generated from PAN carbonisation without sulphur addition showed the highest values of selectivity (up to 400) and adsorption heat (up to 40 kJ mol−1), mainly at low pressures and at low carbon dioxide uptakes, respectively. Furthermore, thanks to their high adsorption capacity, these carbons can be applied for carbon dioxide separation from mixtures with nitrogen

Simultaneous gain and phase profile determination on an interferometric BOTDA

24th International Conference on Optical Fibre Sensors, 96343Y, Curitiba, Brazil, September 28, 2015.Up to now, complex (phase and intensity) measurements in Brillouin Optical Time-Domain Analysis (BOTDA) systems required complex phase modulation methods and high-bandwidth (multi-GHz) detection. In this work, we propose a novel technique that is able to retrieve simultaneously both gain/loss and phase characteristics of the Brillouin interaction by just introducing a Sagnac Interferometer (SI) 011 a standard BOTDA sensing scheme. The technique is described analytically and demonstrated experimentally. With this technique, a reliability increase is produced since redundant measurements can be performed.European CommissionMinisterio de Economía y CompetitividadUniversidad de AlcaláComunidad de MadridGeneralitat Valencian