Faculdade de Ciências da Saúde
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- Large range coherence tuned fiber optic interferometric system for application in accelerometersPublication . Lobo Ribeiro, Antonio B.; Santos, J. L.; Jackson, D. A.A low coherence interferometric system with large tracking range and self‐initialization to be used for remote signal processing of fiber optic accelerometers is investigated. The tracking range of the low coherence system is 1.1 mm at low frequency. Phase resolution better than 1 mrad/√Hz at frequencies below 600 Hz is obtained, with a dynamic range of ≊90 dB. Data are presented which show that if the system were used to process the output from a compliant cylinder‐type accelerometer, resolutions of ∼10−7 g/√Hz could be achieved.
- Simple multiplexing scheme for a fiber-optic grating sensor networkPublication . Jackson, D. A.; Reekie, L.; Archambault, J. L.; Lobo Ribeiro, Antonio B.A new approach for the interrogation of a large number of fiber-optic grating sensors is proposed and demonstrated for a small number of sensors in which signal recovery is achieved by matching a receiving grating to its corresponding sensor. This technique is demonstrated for both quasi-static and periodic measurands, and the resolution achieved for a single sensor–receiving grating pair for quasi-static strain is 4.12 μ∊.
- Isolation and characterization of a cDNA clone from Catharanthus roseus encoding NADPH: cytochrome P-450 reductase, an enzyme essential for reactions catalysed by cytochrome P-450 mono-oxygenases in plantsPublication . Meijer, Annemarie H.; Cardoso, Inês Lopes; Voskuilen, John Th.; de Waal, Anthony; Verpoorte, Robert; Hoge, J. Harry C.The membrane‐bound flavoprotein NADPH:cytochrome P‐450 (cytochrome c) reductase, that functions in electron transfer to cytochrome P‐450 mono‐oxygenases, was purified from a cell suspension culture of the higher plant Catheranthus roseus. Anti‐serum raised against the purified protein was found to inhibit NADPH:cytochrome c reductase activity as well as the activities of the cytochrome P‐450 enzymes geraniol 10‐hydroxylase and trans‐cinnamate 4‐hydroxylase, which are involved in alkaloid biosynthesis and phenylpropanoid biosynthesis, respectively. Immunoscreening of a C. roseus cDNA expression library resulted in the isolation of a partial NADPH: cytochrome P‐450 reductase cDNA clone, which was identified on the basis of sequence homology with NADPH:cytochrome P‐450 reductases from yeast and animal species. The identity of the cDNA was confirmed by expression in Escherichia coli as a functional protein capable of NADPH‐dependent reduction of cytochrome c and neotetrazolium, two in vitro substrates for the reductase. The N‐terminal sequence of the reductase, which was not present in the cDNA clone, was determined from a genomic NADPH: cytochrome P‐450 reductase clone. It was demonstrated that the reductase probably is encoded by a single copy gene. A sequence comparison of this plant NADPH:cytochrome P‐450 reductase with the corresponding enzymes from yeast and animal species showed that functional domains involved in binding of the cofactors FMN, FAD and NADPH are highly conserved between all kingdoms. In C. roseus cell cultures a rapid increase of the reductase steady state mRNA level was observed after the addition of fungal elicitor preparations that are known to induce cytochrome P‐450‐dependent biosynthetic pathways.
- Low coherence fiber optic system for remote sensors illuminated by a 1.3 μm multimode laser diodePublication . Lobo Ribeiro, Antonio B.; Jackson, D. A.A fiber optic sensor probe, with two low‐finesse Fabry–Perot cavities enabling the determination of displacement (in the range of a typical diaphragm pressure sensor) and temperature, is described. The sensors are connected in a reflective array network and their status is read using coherence tuned sensing based upon a multimode laser diode at 1.3 μm wavelength. Data are presented which show the resolution and linearity of the sensors for the measurement of displacement and temperature.
- All‐fiber traveling‐wave laser with nonreciprocal ring configurationPublication . Okhotnikov, O. G.; Lobo Ribeiro, Antonio B.; Salcedo, J. R.An all‐fiber ring laser geometry in the form of a nonreciprocal S‐ring is presented and demonstrated. Its operation is demonstrated to allow unidirectional laser oscillation. The intensity ratio for laser oscillation in each of the two directions were measured, and found to be larger than 150. This value is the largest such ratio obtained for a ring laser without Faraday isolators.
- Demultiplexing of fibre Bragg grating temperature and strain sensorsPublication . Brady, G.P.; Hope, S.; Lobo Ribeiro, Antonio B.; Webb, D.J.; Reekie, L.; Archambault, J.L.; Jackson, D.A.We describe a demultiplexing scheme for fibre optic Bragg grating sensors in which signal recovery is achieved by locking each sensor grating to a corresponding receiver grating. As a demonstration, the technique is applied to strain and temperature sensing, achieving a resolution of 3.0 με and 0.2°C, respectively.
- Multiplexing interrogation of interferometric sensors using dual multimode laser diode sources and coherence readingPublication . Lobo Ribeiro, Antonio B.; Rao, Y.J.; Jackson, D.A.A multiplexing topology with virtually no cross-talk is demonstrated for a sensor network based upon low coherence interferometry, in which a scanning interferometer simultaneously interrogates all the sensors. Dual wavelength operation using two multimode laser diode sources is implemented. The concept is demonstrated by multiplexing two bulk optical Michelson interferometers. For both sensors the achieved resolution was of the order of 1 nm, with a working range of 45 μm.
- Progressive ladder network topology combining interferometric and intensity fiber-optic-based sensorsPublication . Lobo Ribeiro, Antonio B.; Caleya, R. F.; Santos, J. L.Progressive ladder topology is studied by consideration of its properties of power budget and coupler tailoring. Optimization criteria are addressed for lossless and real systems, and their basic characteristics are compared with other topologies. Numerical results are presented, and an experiment is described for the case in which the network supports interferometric and intensity (with referentiation) fiber-optic-based sensors.
- Combined spatial- and time-division-multiplexing scheme for fiber grating sensors with drift-compensated phase-sensitive detectionPublication . Rao, Y. J.; Zhang, L.; Bennion, I.; Lobo Ribeiro, Antonio B.; Jackson, D. A.A combined spatial- and time-division-multiplexing topology with drift-compensated high-resolution wavelength-shift detection is reported for fiber Bragg grating sensors. An eight-element grating sensor array is demonstrated based on this topology. A resolution of ~1.2 microepsilon over a range of ~1.5 mepsilon with a measurement bandwidth of 30 Hz (~0.22 microepsilon/ radicalHz) has been achieved for quasi-static strain measurement.
- Referencing technique for intensity-based sensors using fibre optic Bragg gratingsPublication . Cavaleiro, P.M.; Lobo Ribeiro, Antonio B.; Santos, J.L.An all-optical fibre referencing scheme for intensity based sensors which uses two identical fibre Bragg gratings is described. It provides a general and simple miniature sensor design with referencing directiveness against system power fluctuations. The concept is demonstrated for a reflective-type displacement sensing cavity, and its potential for simultaneous measurand and temperature evaluation is evaluated.