Browsing by Author "Silva, Ricardo M."
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- Interrogation Sensing Scheme Based on a Figure-of-Eight Fiber Loop MirrorPublication . Silva, Ricardo M.; Layeghi, A.; Zibaii, M. I.; Latifi, Hamid; Santos, Jose Luis; Lobo Ribeiro, Antonio B.; Frazao, OrlandoA fiber optic interrogation sensor scheme based on a “figure-of-eight” configuration created from a single directional 3 × 3 fiber optic coupler is proposed. Two loops are formed in each arm and one of them contains the sensing head and the other is used as reference signal. A theoretical study based on Jones matrix analysis of this fiber loop mirror combination is reported. The optical configuration is tested as an interrogation scheme for a fiber strain sensor where the spectral response arises from the combination of the reference signal modulated by the sensor signal. The strain sensor configuration shows a phase sensitivity of 6.7 ± 4.38 × 10−2 mrad/μstrain by linear regression.
- Optical Current Sensors for High Power Systems: A ReviewPublication . Silva, Ricardo M.; Martins, Hugo; Nascimento, Ivo; Baptista, José M.; Lobo Ribeiro, Antonio B.; Santos, José L.; Jorge, Pedro; Frazão, OrlandoThe intrinsic advantages of optical sensor technology are very appealing for high voltage applications and can become a valuable asset in a new generation of smart grids. In this paper the authors present a review of optical sensors technologies for electrical current metering in high voltage applications. A brief historical overview is given together with a more detailed focus on recent developments. Technologies addressed include all fiber sensors, bulk magneto-optical sensors, piezoelectric transducers, magnetic force sensors and hybrid sensors. The physical principles and main advantages and disadvantages are discussed. Configurations and strategies to overcome common problems, such as interference from external currents and magnetic fields induced linear birefringence and others are discussed. The state-of-the-art is presented including commercial available systems.
- A simple, self-referenced, intensity-based optical fibre sensor for temperature measurementsPublication . Silva, Ricardo M.; Baptista, J.M.; Santos, J.L.; Lobo Ribeiro, Antonio B.; Araújo, F.M.; Ferreira, L.A.; Frazão, O.A sensing configuration based on an intensity optical fibre sensor for temperature measurement is reported. Two sensing heads, with identical geometrical configuration, connected in series are implemented. Each sensing head is placed between two fibre Bragg gratings (FBGs), being able to provide a self-referenced measurement, and thus eliminate errors that may arise from undesired intensity fluctuations in the configuration. The first FBG, placed before the aluminium tube, acts as the reference FBG, while the second FBG, placed after the aluminium tube, acts as the signal FBG. It is observed that the amplitude of the signal FBG decays when temperature increases, due to the increase of the ferrules' gap and as result of the material thermal expansion. The temperature response has a behaviour that corresponds to a polynomial fit of third order. The crosstalk between the two sensing heads in series is analysed. The temperature sensitivities obtained in the intervals regions of [36, 48.5] °C and [64, 85] °C are 2.67×10-3 °C-1 and 1.74×10-4 °C-1, respectively. Ten sensing heads with this configuration can be multiplexed in series network topology.
- Suspended-core fibers for sensing applicationsPublication . Frazão, Orlando; Silva, Ricardo M.; Ferreira, Marta S.; Santos, José L.; Lobo Ribeiro, Antonio B.A brief review on suspended-core fibers for sensing applications is presented. A historical overview over the previous ten years about this special designed microstructure optical fiber is described. This fiber presents attractive optical properties for chemical/biological or gas measurement, but it can be further explored for alternative sensing solutions, namely, in-fiber interferometers based on the suspended-core or suspended-multi-core fiber, for physical parameter monitoring.
- Temperature-independent torsion sensor based on “figure-of-eight” fiber loop mirrorPublication . Silva, Ricardo M.; Lobo Ribeiro, Antonio B.; Frazão, OrlandoAn interrogation sensor system combining the “figure-of-eight” fiber loop mirror using a single directional 3×3 fiber optic coupler was proposed. One fiber loop mirror was formed by inserting a length of high birefringent optical fiber at the input ports of the 3×3 coupler. Splicing the output ports of the 3×3 coupler between them created the other fiber loop mirror. The introduction of this second loop gave rise to two polarization states of light with the same frequency but different optical phase. The mechanical torsion sensing head was located at the second loop and was exhibited an average modulus torsion sensitivity of 7.9×10−4 degree/dB. The performance of the sensor was not affected by environmental temperature variations.