2024
Authors
Robalinho, P; Rodrigues, A; Novais, S; Ribeiro, ABL; Silva, S; Frazão, O;
Publication
EPJ Web of Conferences
Abstract
2024
Authors
Soares, L; Novais, S; Ferreira, A; Frazão, O; Silva, S;
Publication
EPJ Web of Conferences
Abstract
2024
Authors
Robalinho, P; Rodrigues, A; Novais, S; Ribeiro, AL; Silva, S; Frazao, O;
Publication
IEEE Sensors Journal
Abstract
The aim of this work is to introduce a novel digital signal processing method for data acquired using Low Coherence Interferometry (LCI) with a 1 kHz actuator oscillation frequency. Convolution and correlation operations are employed as efficient filters, reducing computational complexity for multi-layer filtering. An envelope filtering technique is developed to address discrepancies in peak signal determination caused by non-linear actuator motion. Additionally, a phase linearization method is presented to normalize the peak position relative to the actuator signal. Experimental results demonstrate a significant signal-to-noise ratio (SNR) improvement of 50 dB. Long-term measurements reveal an 11 dB noise reduction for frequencies below 1 mHz. This research enables LCI implementation at sampling rates of at least 1 kHz and expands its applicability to extreme measurement conditions. © 2001-2012 IEEE.
2024
Authors
Robalinho, P; Piaia, V; Soares, L; Novais, S; Ribeiro, AL; Silva, S; Frazao, O;
Publication
SENSORS
Abstract
This paper presents a new type of phase-shifted Fiber Bragg Grating (FBG): the sliced-FBG (SFBG). The fabrication process involves cutting a standard FBG inside its grating region. As a result, the last grating pitch is shorter than the others. The optical output signal consists of the overlap between the FBG reflection and the reflection at the fiber-cleaved tip. This new fiber optic device has been studied as a vibration sensor, allowing for the characterization of this sensor in the frequency range of 150 Hz to 70 kHz. How the phase shift in the FBG can be controlled by changing the length of the last pitch is also shown. This device can be used as a filter and a sensing element. As a sensing element, we will demonstrate its application as a vibration sensor that can be utilized in various applications, particularly in monitoring mechanical structures.
2021
Authors
Perez Herrera, RA; Bravo, M; Leandro, D; Novais, S; Pradas, J; Lopez Amo, M;
Publication
IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS
Abstract
In this work, a multi-parameter point sensor based on the combination of Fabry-Perot (FP) and the anti-resonant (AR) reflecting guidance in cascade configuration is proposed and experimentally demonstrated. This structure, based on FP interference and AR reflecting guidance, was fabricated with two different air micro-cavities. The attained experimental results showed different strain and temperature sensitivities for the antiresonance contribution. However, when analyzing the FP interference, only strain sensitivity was observed, demonstrating that this air micro-cavity was also insensitive to temperature variations.
2018
Authors
Leitao, C; Domingues, MF; Novais, S; Tavares, C; Pinto, J; Marques, C; Antunes, P;
Publication
BIOPHOTONICS: PHOTONIC SOLUTIONS FOR BETTER HEALTH CARE VI
Abstract
Cardiovascular diseases are the main cause of death in the world and its occurrence is closely related to arterial stiffness. Arterial stiffness is commonly evaluated by analysing the arterial pulse waveform and velocity, with electromechanical pressure transducers, in superficial arteries such as carotid, radial and femoral. In order to ease the acquisition procedure and increase the patients comfort during the measurements, new optical fibre techniques have been explored to be used in the reliable detection of arterial pulse waves, due to their small size, high sensitivity, electrical isolation and immunity to electromagnetic interference. More specifically, fibre Bragg gratings (FBGs) are refractive index modulated structures engraved in the core of an optical fibre, which have a well-defined resonance wavelength that varies with the strain conditions of the medium, known as Bragg wavelength. In this work, FBGs were embedded in a commercial resin, producing films that were used to assess the arterial pulse in superficial locations such as carotid, radial and foot dorsum. The technique proved to be a promising, comfortable and trustworthy way to assess the arterial pulses, with all the optical fibre use advantages, in a non-intrusive biomedical sensing procedure. Examples of possible applications of the developed structures are smart skin structures to monitor arterial cardiovascular parameters, in a stable and reliable way, throughout daily activities or even during exams with high electromagnetic fields, such as magnetic resonance imaging.
The access to the final selection minute is only available to applicants.
Please check the confirmation e-mail of your application to obtain the access code.