Dr. Paulo Caldas

Instituto Politécnico de Viana do Castelo

Dr. Paulo Caldas

Instituto Politécnico de Viana do Castelo

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Academic Career Length

24Years (2003-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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15 October 2007 in Optics Letters

Journal Article

All-fiber Mach-Zehnder curvature sensor based on multimode interference combined with a long-period grating

F. M. Araújo

F. Farahi

A novel Mach–Zehnder interferometer based on a fiber multimode interference structure combined with a long-period fiber grating (LPG) is proposed. The multimode interference is achieved through the use of a MMF section spliced between two single-mode fibers, with a length adjusted to couple a fraction of light into the cladding modes. A LPG placed after the MMF couples light back into the fiber core, completing the Mach–Zehnder interferometer. This novel configuration was demonstrated as a bending sensor.

9 June 2011 in Applied Optics

Journal Article

Fiber optic hot-wire flowmeter based on a metallic coated hybrid long period grating/fiber Bragg grating structure

Francisco Araújo

In this work an all-optical hot-wire flowmeter based on a silver coated fiber combining a long period grating and a fiber Bragg grating (FBG) structure is proposed. Light from a pump laser at

1480 nm

propagating down the fiber is coupled by the long period grating into the fiber cladding and is absorbed by the silver coating deposited on the fiber surface over the Bragg grating structure. This absorption acts like a hot wire raising the fiber temperature locally, which is effectively detected by the FBG resonance shift. The temperature increase depends on the flow speed of the surrounding air, which has the effect of cooling the fiber. It is demonstrated that the Bragg wavelength shift can be related to the flow speed. A flow speed resolution of

0.08 m / s

is achieved using this new configuration.

1 September 2004 in Sensors and Actuators B: Chemical

Journal Article

Optical fiber probes for fluorescence based oxygen sensing

J.L. Santos

1 October 2009 in Optics Express

Journal Article

Modal interferometer based on hollow-core photonic crystal fiber for strain and temperature measurement

S. H. Aref

R. Amezcua-Correa

J. P. Carvalho

Orlando Frazão

Paulo Caldas

J. C. Knight

In this work, sensitivity to strain and temperature of a sensor relying on modal interferometry in hollow-core photonic crystal fibers is studied. The sensing structure is simply a piece of hollow-core fiber connected in both ends to standard single mode fiber. An interference pattern that is associated to the interference of light that propagates in the hollow core fundamental mode with light that propagates in other modes is observed. The phase of this interference pattern changes with the measurand interaction, which is the basis for considering this structure for sensing. The phase recovery is performed using a white light interferometric technique. Resolutions of ± 1.4µε and ± 0.2°C were achieved for strain and temperature, respectively. It was also found that the fiber structure is not sensitive to curvature.

11 August 2009 in Optics Letters

Journal Article

Fabry-Perot refractometer based on an end-of-fiber polymer tip

C. Turck

A micrometric Fabry–Perot refractometer based on an end-of-fiber polymer tip is proposed. The fiber tip, with a length of

36 μ m

, was fabricated by self-guiding photopolymerization. The two-wave interferometric operation was achieved by combining the light waves generated at the interface between the single-mode fiber and the polymer tip, and at the fiber tip end (Fresnel reflection). The Fabry–Perot interferometer is coherence addressed and heterodyne interrogated, resulting into a liquid refractive index resolution of

\approx 7.5 \times 10^{- 4}

3 July 2007 in Optics Letters

Journal Article

Optical flowmeter using a modal interferometer based on a single nonadiabatic fiber taper

Orlando Frazão

Paulo Caldas

F. M. Araújo

L. A. Ferreira

José Luís Santos

A novel in-fiber modal interferometer is presented that is based on a nonadiabatic biconical fused taper that couples light between the cladding and the core, combined with the Fresnel reflection at the fiber end. It is observed that the returned light from this fiber structure shows a channeled spectrum similar to that of a two-wave Michelson interferometer. The application of this device as a fiber optic flowmeter sensor is demonstrated.

About Me

Paulo Caldas. He completed his PhD in Physics in 2011 at Universidade do Porto, Master in Master in Optoelectronics and Lasers in 2003 by Universidade do Porto and Bachelor in Applied Physics-Optical Branch in 1999 at Universidade do Porto Minho. He is an Adjunct Professor at the Polytechnic Institute of Viana do Castelo Higher School of Technology and Management and Researcher at Instituto de Engenharia de Sistemas e Computadores Tecnologia e Ciência. He has published 95 articles in specialized jornal and international conferences. Received 7 awards and / or honors. He works in the area (s) in Physics with emphasis in Optics and Engineering Sciences with interesting in long period gratings, optical fibers, optical fiber sensors, interferometers, whispering gallery modes, microresonators, optical fiber communications. In his professional activities interacted with 162 collaborator (s) in coauthoring of scientific works.

Dr. Paulo Caldas

Dr. Paulo Caldas

Research Focus & Metrics

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Representative Publications

About Me