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Sobre

Sobre

Licenciado  em Física - Óptica pela Universidade do Minho (1999), obteve um Mestrado em Optoelectrónica e Laser pela Faculdade de Ciências da Universidade do Porto (2003 e Doutoramento em Física pela Faculdade de Ciências da Universidade do Porto (2011). É Professor Adjunto no Instituto Politécnico de Viana do Castelo e Investigador Afliado no Centro de Fotónica Aplicada do INESC TEC. É autor e co-autor de mais de 80 artigos científicos relacionados com sensores em fibras ópticas, whispering gallery modes e redes de  período longo

Tópicos
de interesse
Detalhes

Detalhes

  • Nome

    Paulo Caldas
  • Cargo

    Investigador Sénior
  • Desde

    01 outubro 1998
  • Nacionalidade

    Portugal
  • Centro

    Fotónica Aplicada
  • Contactos

    +351220402301
    paulo.caldas@inesctec.pt
Publicações

2025

Normalized temperature sensitivity of fiber Bragg gratings inscribed under different conditions

Autores
Preizal, J; Cosme, M; Pota, M; Caldas, P; Araujo, FM; Oliveira, R; Nogueira, R; Rego, GM;

Publicação
29TH INTERNATIONAL CONFERENCE ON OPTICAL FIBER SENSORS

Abstract
In this paper we present results on the normalized temperature sensitivity of UV- and fs-induced fiber Bragg gratings in a singlemode fiber with similar to 4.7 mol% GeO2 and having an Ormocer coating. In the 1500-1600 nm wavelength range, the former shows an almost constant value of 6.165x10(-6) K-1, whilst the fs-induced present some variation not related with the strength of the grating but probably due to induced birefringence. The average value obtained was 6.191x10(-6) K-1 which is higher than the former. For the UV-induced gratings in the Corning SMF-28 fiber (3.67 mol% GeO2) the value obtained was 6.143x10(-6) K-1. The achieved values are compatible with the use of Corning 7980 silica-based cladding fiber. Preliminary results also show no measurable impact of the hydrogenation process or the strength of the grating on the normalized temperature sensitivity.

2025

Semi-distributed optical fiber bending extensometer system for precision landslide monitoring based on OTDR

Autores
Lorenzo Santini; Paulo Caldas; Luís C. Coelho;

Publicação
29TH INTERNATIONAL CONFERENCE ON OPTICAL FIBER SENSORS

Abstract
A semi-distributed optical fiber bending extensometer system based on OTDR is proposed, consisting of N-loops designed to enable different maximum extension measurements and sensitivities. This system offers a low-cost solution for monitoring landslides and similar civil structures. Tests conducted at 1625 nm demonstrate that different series of sensors can be independently measured with elongation errors typically within +/- 0.25 cm across a range from 0 to 9 cm.

2025

Flexible Wearable Optical Sensor Based on a Balloon-like Interferometer to Breathing Monitoring

Autores
Costa, MN; Cardoso, VHR; de Souza, MFC; Caldas, P; Giraldi, MTR; Frazao, O; Santos, J; Costa, JCWA;

Publicação
29TH INTERNATIONAL CONFERENCE ON OPTICAL FIBER SENSORS

Abstract
A flexible wearable sensor utilizing a balloon-shaped interferometer structure, created from a bent standard single-mode fiber and a 3D-printed piece, was introduced and shown for respiratory monitoring. The interferometer is a compact, cost-effective, and easily fabricated sensor. The fiber's curvature causes interference between the core and cladding modes, which in turn results in the sensor operation. In the balloon-shaped curving section, light traversing the core partially escapes and interacts with the cladding. The preliminary results demonstrate an average displacement of 9.3 nm and the capability to evaluate breathing rate.

2025

Design and testing of a probe for diameter variation measurement based on fiber Bragg grating combined with additive manufacturing

Autores
Cardoso, VHR; Caldas, P; Giraldi, MTR; Fernandes, CS; Frazao, O; Costa, JCWA; Santos, JL;

Publicação
SENSORS AND ACTUATORS A-PHYSICAL

Abstract
A sensor based on the fiber Bragg grating (FBG) and additive manufacturing for diameter variation measurement is proposed and experimentally demonstrated in this work. Two designs were proposed: a FBG alone and a FBG in series with a spring. Three tests were developed for each design, and at the end, the statistical treatment was performed. The designs were fabricated using a 3D printer, and the FBG sensor is embedded. The results demonstrated that the structures proposed in this work can be used to monitor diameter variation, among other applications. The sensors, with and without spring in series, presented sensitivities of 0.0671 nm/mm and 0.5116 nm/mm, respectively, with a good linear response greater than 0.99.

2024

A century on diameter measurement techniques in cylindrical structures

Autores
Cardoso, VHR; Caldas, P; Giraldi, MTR; Cernadas, ML; Fernandes, CS; Frazao, O; Costa, JCWA; Santos, JL;

Publicação
MEASUREMENT SCIENCE AND TECHNOLOGY

Abstract
This work addresses the historical development of techniques and methodologies oriented to the measurement of the internal diameter of transparent tubes since the original contributions of Anderson and Barr published in 1923 in the first issue of Measurement Science and Technology. The progresses on this field are summarized and highlighted the emergence and significance of the measurement approaches supported by the optical fiber.