Educação matemática pela arte
Gusmão, Lucimar Donizete
2013-08-28
Search results
12 records were found.
We describe a compact, pulsed, broadband source for sensing using ASE from Er gas detection.
We describe a compact, pulsed, broadband source for sensing using ASE from Er gas detection.
Results from simulations of the response of a methane gas sensor using optical correlation spectroscopy (CoSp) are presented. Predictions of the sensor response, signal/noise performance and detection sensitivity are made for a typical fibre optic-coupled system . Spectral absorption data of the gases is obtained from the publicly available HITRAN database. Emphasis is placed on the effects on the detection sensitivity of varying (a)the optical filter characteristics, i.e. center wavelength and bandwidth, and (b)the concentration (partial pressure) of CH, a theoretical noise-limited detection limit below 1 ppm is predicted.
The cross-sensitivity to water vapor is derived and compared to that which would occur with a conventional broadband absorption method, i.e. one that would not exhibit the same selectivity as the CoSp method. This...
We present a comprehensive model of a CO2 correlation spectroscopy based gas sensor. Predictions of the sensor response for typical fibre optic-coupled systems are made, taking into account effects of noise in detected signals.
This paper describes recent experimental results on the detection of carbon dioxide and methane gases using the complementary source modulation (CoSM) method, the topology of which is shown in figure 1, and compares these with numerical simulations from data derived from the HITRAN database. There is a particular interest in sensors using optical fibres coupled to a passively coupled sensing head. CO have reasonably strong absorption bands in the 2.0 μm and 2.3 μm spectral regions respectively. That of methane in the 2.3 μm band is less suited for propagation over fibre lengths greater than a few metres, so the somewhat weaker absorption band at 1.6 μm is more suited to sensing over extended fibre networks. Analyses have been conducted for both of these gases and results will be presented for the prediction of modulation index, signal/...
We present a distributed amplified hybrid dense wavelength division multiplexing (DWDM) and time division multiplexing (TDM) array architecture for large scale interferometric fiber-optic sensor array systems. This architecture employs a distributed Erbium doped fiber amplifier (EDFA) scheme to decrease the distribution loss among multiplexed wavelengths, and employs TDM at each wavelength to increase the total number of sensors that can be supported. The first experimental demonstration of this system is reported including results which show the potential for multiplexing and interrogating up to 4096 sensors using a single telemetry fiber pair with good system performance. The number of interrogation sensors could be further increased by increasing the number of wavelength channels. These architectures would be of great importance in ...
We present an analytical approach to accurately model the phase sensitivity, and provide simple analytical formulae, useful in the design, comparison and optimization of multiplexed amplified interferometric fiber-optic based sensor systems. The phase sensitivity model incorporates the various key noise contributions including receiver noise, amplified spontaneous emission (ASE) induced noise, active sources noise and other phase noise terms. We define and present a novel term 'Demod phase sensitivity' to take into account the effects from noise aliasing in systems based on time division multiplexed (TDM) architectures. An experiment was conducted that confirmed the appropriateness and accuracy of the phase sensitivity model. The approach is widely applicable but particular appropriate for fiber-optic sensor systems using amplifiers an...
A new optical luminescent-lifetime pH sensor based on the sol-gel doped europium chelate has been developed. Near-UV to visible (350.400 nm) excitation of the europium(III) chelate of a 4-trifluoromethylcarbostyril derivative of diethylenetriaminepentaacetic acid (DTPA) exhibits a typical lanthanide line-like emission, the highest peak being at 615 nm. Due to antenna-mediated effects, the heterocyclic chromophore (parent emission at 450 nm) transfers its energy to the close europium having isolated very weak quantum efficiency. The complex was co-immobilized with the non-fluorescent pH indicator bromothymol blue (BTB) in a semi-permeable sol-gel layer. It can be shown, that not only the line emission spectra but also decay lifetimes depend strongly on pH changes. Since the sensitive dyestuff is highly stable and not quenched by oxygen,...
It is of great importance to develop gas sensing techniques which are selective, quantitative, fast-acting and not susceptible to poisoning. Spectroscopic optical gas sensors, especially those capable of remote sensing over optical fibres, are highly attractive for fast real-time detection and measurement of many gases [1]. One highly selective optical gas sensing method is correlation spectroscopy (CS) [2], in which a reference sample of target gas is held fixed within the interrogation system to act as a spectral reference, and is then compared with the spectrum of the test gas to obtain the measurement. We have suggested that a Photonic Bandgap Fibre (PBGF), filled with the target gas, provides a very effective and compact reference, with a clear advantage over traditional linear cells, which are bulky, intricate, fragile, difficult...
We present results from the first optical fibre correlation spectroscopy gas sensor which uses no lenses other than in the measurement gas cell. The sensor measures acetylene (C2H2) gas concentration. A 1-m length of photonic bandgap fibre (PBGF) was filled with acetylene at atmospheric pressure, then fusion spliced to standard, solid-core, single-mode SMF-28 fibre to form a compact, coilable, reference cell without the need for any lenses or bulk optics. As the cell contained a gas volume <5 μL, it presents a greatly reduced hazard even when filled with explosive or harmful gases. Acetylene concentration measurements were made by comparing the absorption spectrum of this reference cell with that of a bulk optics measurement cell containing test gases, using a simple sensing topology requiring no spectrally selective components. Our se...
