Browsing by Author "Ferreira, L A"
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- Analysis of the reflective-matched fiber Bragg grating sensing interrogation schemePublication . Lobo Ribeiro, Antonio B.; Ferreira, L A; Santos, J L; Jackson, D AA technique for the demodulation of fiber Bragg grating (FBG) sensors based on the use of a second wavelength-matched FBG receiver to track wavelength shifts from the FBG sensor is analyzed, particularly regarding its sensitivity as determined by primary noise sources. Numerical and experimental results show that there is an optimum Bragg wavelength difference between the two FBG's that maximizes the sensitivity for this demodulation technique.
- Electrical current metering with a dual interferometric configuration and serrodyne signal processingPublication . Jorge, P A S; Caldas, P.; Ferreira, L A; Lobo Ribeiro, Antonio B.; Santos, J L; Farahi, FA bulk interferometric configuration for electrical current remote sensing in high voltage environments based on the Faraday effect is described. The combination of Sagnac’s reciprocal properties with a Mach–Zehnder processing interferometer in the same sensing head is used to implement serrodyne processing for current sensing. A theoretical analysis based on the Jones matrix is presented. Experimental results that validate the exploited concept are obtained, showing linearity up to 1800Arms and waveform reproduction at 50 Hz. The possibility of using the proposed interferometric concept to simultaneously fulfil the requirements associated with metering and relaying applications is also addressed.
- Simultaneous displacement and temperature sensing using a white light interrogated low finesse cavity in line with a fiber Bragg gratingPublication . Ferreira, L A; Lobo Ribeiro, Antonio B.; Santos, J L; Farahi, FA fiber optic sensing system for simultaneous measurement of displacement and temperature is presented. It is based on the use of a low finesse extrinsic Fabry-Pérot cavity and a fiber Bragg grating for temperature compensation. A while light tandem interferometric technique is used to recover the signal from the low fitnesse cavity, providing both fringe visibility and phase measurements. These, together with the fiber grating signal, give two equations that can be used to simultaneously determine temperature and displacement Theoretical analysis of the sensing scheme is performed. Experimental results are presented which validate theoretical predictions and also demonstrate the feasibility of this sensing system in practical applications.