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Dr. Paulo Caldas
Instituto Politécnico de Viana do Castelo

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Research Keywords & Expertise

0 Interferometry
0 Optical Communications
0 long period fiber grating
0 optical fibers
0 optical fiber sensors

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long period fiber grating
Interferometry
Optical Communications
optical fibers
optical fiber sensors

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Short Biography

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.

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Profile ImageDiana Viegas Univ. do Porto (Portugal)
Profile ImageJoão Coelho Faculdade de Ciências da Un...
Profile ImageCatarina Silva Univ. de Lisboa (Portugal)
Profile ImagePaula A.R. Tafulo INESC Porto (Portugal)
Profile ImagePedro Pinto Instituto Politécnico de Vi...
Profile ImageJoaquim C.G. Esteves Da Silva Department of Geosciences, E...
Profile ImageJoão De Lemos Pinto Department of Physics and I3...
Profile ImageOlivier Soppera Université de Haute-Alsace,...
Profile ImageLuis Coelho INESC TEC - Technology and S...
Profile ImageJ. Viegas Masdar Institute of Science ...
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Review
Published: 19 July 2021 in Sensors
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In this work, we reviewed the most important achievements of INESC TEC related to the fabrication of long-period fiber gratings using the electric arc technique. We focused on the fabrication setup, the type of fiber used, and the effect of the fabrication parameters on the gratings’ transmission spectra. The theory was presented, as well as a discussion on the mechanisms responsible for the formation of the gratings, supported by the measurement of the temperature reached by the fiber during an electric arc discharge.

ACS Style

Gaspar Rego; Paulo Caldas; Oleg Ivanov. Arc-Induced Long-Period Fiber Gratings at INESC TEC. Part I: Fabrication, Characterization and Mechanisms of Formation. Sensors 2021, 21, 4914 .

AMA Style

Gaspar Rego, Paulo Caldas, Oleg Ivanov. Arc-Induced Long-Period Fiber Gratings at INESC TEC. Part I: Fabrication, Characterization and Mechanisms of Formation. Sensors. 2021; 21 (14):4914.

Chicago/Turabian Style

Gaspar Rego; Paulo Caldas; Oleg Ivanov. 2021. "Arc-Induced Long-Period Fiber Gratings at INESC TEC. Part I: Fabrication, Characterization and Mechanisms of Formation." Sensors 21, no. 14: 4914.

Journal article
Published: 18 December 2020 in Optical Fiber Technology
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A strain gauge sensor based on Fiber Bragg Grating (FBG) for diameter measurement is proposed and experimentally demonstrated. The sensor is easily fabricated inserting the FBG on the strain gauge—it was fabricated using a 3D printer—and fixing the FBG in two points of this structure. The idea is to vary the diameter of the structure. We developed two experimental setups, the first one is used to evaluate the response of the FBG to strain and the second one to assess the possibility of using the structure developed to monitor the desired parameter. The results demonstrated that the structure can be used as a way to monitor the diameter variation in some applications. The sensor presented a sensitivity of 0.5361 nm/mm and a good linear response of 0.9976 using the Strain Gauge with FBG and fused taper.

ACS Style

Victor H.R. Cardoso; Paulo Caldas; M. Thereza R. Giraldi; Orlando Frazão; Claudio J. Reis de Carvalho; João C.W.A. Costa; José L. Santos. Experimental investigation of a strain gauge sensor based on Fiber Bragg Grating for diameter measurement. Optical Fiber Technology 2020, 61, 102428 .

AMA Style

Victor H.R. Cardoso, Paulo Caldas, M. Thereza R. Giraldi, Orlando Frazão, Claudio J. Reis de Carvalho, João C.W.A. Costa, José L. Santos. Experimental investigation of a strain gauge sensor based on Fiber Bragg Grating for diameter measurement. Optical Fiber Technology. 2020; 61 ():102428.

Chicago/Turabian Style

Victor H.R. Cardoso; Paulo Caldas; M. Thereza R. Giraldi; Orlando Frazão; Claudio J. Reis de Carvalho; João C.W.A. Costa; José L. Santos. 2020. "Experimental investigation of a strain gauge sensor based on Fiber Bragg Grating for diameter measurement." Optical Fiber Technology 61, no. : 102428.

Conference paper
Published: 20 August 2020 in EPJ Web of Conferences
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In this work, a long-period fiber grating (LPG) based sensor was evaluated as a sensing device for micro-force measurement, in the order of micro Newtons. It was used an LPG fabricated by arc-inducted technique in a SMF-28 standard optical fiber. The optical fiber was fixed between two clamps with a separation of 150 mm with the middle of the LPG located at the center. Characterizations were performed in terms of temperature, curvature and strain. The grating was then used as a micro-force sensor by means of both curvature and strain, induced by a hung mass in a stretched fiber. Furthermore, the evaluation of a precurvature LPG was performed to assess if an increase of sensitivity is achieved. Micro-force sensitivity achieved with the stretched LPG was 1.41 nm/mN and it was demonstrated that its sensitivity can be enhanced to 5.14 nm/mN with a pre-curvature of 2.2 m–1 applied to the LPG, achieving a spectral resolution of at least 15.6 μN.

ACS Style

Walter S. J. Ferreira; Paulo S. S. Dos Santos; Paulo Caldas; Pedro A. S. Jorge; João M. S. Sakamoto. Micro-force measurement with pre-curvature long-period fiber grating-based sensor. EPJ Web of Conferences 2020, 238, 12009 .

AMA Style

Walter S. J. Ferreira, Paulo S. S. Dos Santos, Paulo Caldas, Pedro A. S. Jorge, João M. S. Sakamoto. Micro-force measurement with pre-curvature long-period fiber grating-based sensor. EPJ Web of Conferences. 2020; 238 ():12009.

Chicago/Turabian Style

Walter S. J. Ferreira; Paulo S. S. Dos Santos; Paulo Caldas; Pedro A. S. Jorge; João M. S. Sakamoto. 2020. "Micro-force measurement with pre-curvature long-period fiber grating-based sensor." EPJ Web of Conferences 238, no. : 12009.

Conference paper
Published: 20 August 2020 in EPJ Web of Conferences
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A method based on multiple Fiber Bragg Gratings (FBG) and a structure fabricated using a 3D printer for diameter measurement is proposed and experimentally demonstrated. The sensor is easily developed inserting the FBG on the structure and fixing the FBG in two points. Due to this arrangement, when the diameter is reduced a force is applied on the sensor and this causes a wavelength shift. The study is divided in two steps using one experimental setup. At first, each FBG response is independently evaluated concerning the diameter variation and after that, the FBGs are evaluated together. The results demonstrated that the structure can be used as a way to monitor the diameter variation in some applications.

ACS Style

Victor Cardoso; Paulo Caldas; M. Giraldi R. Thereza; Orlando Frazão; Claudio Carvalho; João Costa; José L. Santos. Sensor Based on Multiple Fiber Bragg Gratings for Diameter Measurement. EPJ Web of Conferences 2020, 238, 12013 .

AMA Style

Victor Cardoso, Paulo Caldas, M. Giraldi R. Thereza, Orlando Frazão, Claudio Carvalho, João Costa, José L. Santos. Sensor Based on Multiple Fiber Bragg Gratings for Diameter Measurement. EPJ Web of Conferences. 2020; 238 ():12013.

Chicago/Turabian Style

Victor Cardoso; Paulo Caldas; M. Giraldi R. Thereza; Orlando Frazão; Claudio Carvalho; João Costa; José L. Santos. 2020. "Sensor Based on Multiple Fiber Bragg Gratings for Diameter Measurement." EPJ Web of Conferences 238, no. : 12013.

Conference paper
Published: 01 January 2018 in 26th International Conference on Optical Fiber Sensors
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This paper presents preliminary results of common water thermal conductivity measurements using an all-fiber sensor based in conventional hot-wire method concept. The thermal conductivity of common water at room temperature obtained is 0.699 W/mK. Although the result is relatively distinct, about 14%, from the reference value found in literature, it is promising and indicates the feasibility of using the experimental arrangement for measuring thermal properties of materials with higher accuracy, provided that improvements already foreseen in future work be incorporated.

ACS Style

G. E.Silva; P. Caldas; J. L. Santos. Measurement Thermal Conductivity of Water using a All-Fiber Sensor Based on a Metallic Coated Hybrid LPG-FBG Structure. 26th International Conference on Optical Fiber Sensors 2018, WF38 .

AMA Style

G. E.Silva, P. Caldas, J. L. Santos. Measurement Thermal Conductivity of Water using a All-Fiber Sensor Based on a Metallic Coated Hybrid LPG-FBG Structure. 26th International Conference on Optical Fiber Sensors. 2018; ():WF38.

Chicago/Turabian Style

G. E.Silva; P. Caldas; J. L. Santos. 2018. "Measurement Thermal Conductivity of Water using a All-Fiber Sensor Based on a Metallic Coated Hybrid LPG-FBG Structure." 26th International Conference on Optical Fiber Sensors , no. : WF38.

Abstract
Published: 01 January 2017 in Proceedings
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High data rate optical fiber links are usually deployed in core IP networks to transport bulky

ACS Style

Nelson Sotomaior; Bruno Teixeira; Joao Azevedo; Paulo Caldas; Gaspar Rego; Pedro Pinto. Optical Fiber Link Failure Prediction System Based on Long-Period Fiber Grating Mechanical Sensor. Proceedings 2017, 1, 1116 .

AMA Style

Nelson Sotomaior, Bruno Teixeira, Joao Azevedo, Paulo Caldas, Gaspar Rego, Pedro Pinto. Optical Fiber Link Failure Prediction System Based on Long-Period Fiber Grating Mechanical Sensor. Proceedings. 2017; 1 (8):1116.

Chicago/Turabian Style

Nelson Sotomaior; Bruno Teixeira; Joao Azevedo; Paulo Caldas; Gaspar Rego; Pedro Pinto. 2017. "Optical Fiber Link Failure Prediction System Based on Long-Period Fiber Grating Mechanical Sensor." Proceedings 1, no. 8: 1116.

Journal article
Published: 10 March 2016 in Journal of Lightwave Technology
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We demonstrated the possibility to inscribe long-period fiber gratings (LPFGs) in a B/Ge codoped fiber by using grating periods shorter than 150 μm. We also have arc-induced in the SMF 28 fiber an LPFG in the dispersion turning points by using a grating period of 197 μm. In previous works, the shortest periods were, respectively, of the order of 190 and 320 μm for the same fibers. To achieve such a considerable reduction in the grating periods which enables access to the higher order cladding modes (higher sensitivity), we have developed a high-voltage power supply that allows for a constant and stable electric current ranging from 10.5 up to 21 mA. Computer simulations were used to identify the cladding mode resonances for each grating inscribed in the different fibers. The fabricated LPFGs were characterized as a function of the external refractive index from 1.33 up to 1.42, and an average refractive index sensitivity of -720 nm/RIU in the 1.33-1.41 range was obtained for a 192-μm LPFG without further optimization, such as the use of etching or thin films deposition.

ACS Style

Celso Colaco; Paulo Caldas; Ignacio Del Villar; Rui Chibante; Gaspar Rego. Arc-Induced Long-Period Fiber Gratings in the Dispersion Turning Points. Journal of Lightwave Technology 2016, 34, 4584 -4590.

AMA Style

Celso Colaco, Paulo Caldas, Ignacio Del Villar, Rui Chibante, Gaspar Rego. Arc-Induced Long-Period Fiber Gratings in the Dispersion Turning Points. Journal of Lightwave Technology. 2016; 34 (19):4584-4590.

Chicago/Turabian Style

Celso Colaco; Paulo Caldas; Ignacio Del Villar; Rui Chibante; Gaspar Rego. 2016. "Arc-Induced Long-Period Fiber Gratings in the Dispersion Turning Points." Journal of Lightwave Technology 34, no. 19: 4584-4590.

Conference paper
Published: 28 September 2015 in 24th International Conference on Optical Fibre Sensors
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ACS Style

C. Colaço; P. Caldas; R. Chibante; Gaspar Rego. Arc-induced gratings in the turning points. 24th International Conference on Optical Fibre Sensors 2015, 96346K -96346K-4.

AMA Style

C. Colaço, P. Caldas, R. Chibante, Gaspar Rego. Arc-induced gratings in the turning points. 24th International Conference on Optical Fibre Sensors. 2015; ():96346K-96346K-4.

Chicago/Turabian Style

C. Colaço; P. Caldas; R. Chibante; Gaspar Rego. 2015. "Arc-induced gratings in the turning points." 24th International Conference on Optical Fibre Sensors , no. : 96346K-96346K-4.

Conference paper
Published: 01 January 2015 in PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON NUMERICAL ANALYSIS AND APPLIED MATHEMATICS 2014 (ICNAAM-2014)
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Long-period gratings is class of fiber gratings, in which the period of the refractive index modulation is such that it satisfies a phase matching condition between the fundamental core mode and forward propagating cladding modes of an optical fiber.Many applications in optical communications and optical fiber sensing have been reported along the last years. In this work we present a simulation tool for determining LPG transmission spectrum and the coupling curve. The simulation tool uses MatLab code. The software produces also estimations of the resonant wavelength displacement due to changes in external parameters like temperature or external refractive index. A simple comparison between the simulation and the experimental result show that exist a good agreement with results obtain.

ACS Style

Fábio D. Baptista; Ariel Guerreiro; Luís A. Gomes; Paulo Caldas. Simulation of long period fibre gratings and applications. PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON NUMERICAL ANALYSIS AND APPLIED MATHEMATICS 2014 (ICNAAM-2014) 2015, 1648, 710010 .

AMA Style

Fábio D. Baptista, Ariel Guerreiro, Luís A. Gomes, Paulo Caldas. Simulation of long period fibre gratings and applications. PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON NUMERICAL ANALYSIS AND APPLIED MATHEMATICS 2014 (ICNAAM-2014). 2015; 1648 ():710010.

Chicago/Turabian Style

Fábio D. Baptista; Ariel Guerreiro; Luís A. Gomes; Paulo Caldas. 2015. "Simulation of long period fibre gratings and applications." PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON NUMERICAL ANALYSIS AND APPLIED MATHEMATICS 2014 (ICNAAM-2014) 1648, no. : 710010.

Journal article
Published: 18 December 2014 in Journal of Lightwave Technology
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In this study, we investigated the temperature behavior of phase-shifted long-period fiber gratings (PS-LPFGs) inscribed in two types of optical fiber: B/Ge and SMF28. The experiments were carried out from 5 to 305 K using a superconducting quantum interference device magnetometer. The average temperature sensitivity obtained of -0.43 nm/K for PS-LPFGs inscribed in the B/Ge fiber is one order of magnitude larger than for PS-LPFGs inscribed in the SMF28 fiber, in the 60-240 K range. Values ranging from -0.08 nm/K up to 0.2 nm/K were obtained in the 5-35 K temperature range, which are considerably better than previous results achieved for metal-coated FBGs and also for LPFGs inscribed in a similar B/Ge codoped fiber. Nevertheless, further work is required in order to correctly address sensor reliability.

ACS Style

Raquel Martins; Paulo Caldas; Bruno Teixeira; Joao Azevedo; Jose Monteiro; Joao H. Belo; João Pedro Esteves de Araújo; Jose L. Santos; Gaspar Rego. Cryogenic Temperature Response of Reflection-Based Phase-Shifted Long-Period Fiber Gratings. Journal of Lightwave Technology 2014, 33, 2511 -2517.

AMA Style

Raquel Martins, Paulo Caldas, Bruno Teixeira, Joao Azevedo, Jose Monteiro, Joao H. Belo, João Pedro Esteves de Araújo, Jose L. Santos, Gaspar Rego. Cryogenic Temperature Response of Reflection-Based Phase-Shifted Long-Period Fiber Gratings. Journal of Lightwave Technology. 2014; 33 (12):2511-2517.

Chicago/Turabian Style

Raquel Martins; Paulo Caldas; Bruno Teixeira; Joao Azevedo; Jose Monteiro; Joao H. Belo; João Pedro Esteves de Araújo; Jose L. Santos; Gaspar Rego. 2014. "Cryogenic Temperature Response of Reflection-Based Phase-Shifted Long-Period Fiber Gratings." Journal of Lightwave Technology 33, no. 12: 2511-2517.

Conference paper
Published: 02 June 2014 in 23rd International Conference on Optical Fibre Sensors
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In this paper it is presented an all-fiber implementation of the hot-wire needle probe concept, widely used to measure the thermal properties of materials, particularly the thermal conductivity. It is based on the heating of a metal thin film deposited on the surface of the fiber induced by the coupling of laser light into the cladding via a long period grating, and determination, using a fiber Bragg grating, of the time dependence of the temperature of the surrounding medium at a fixed distance of the fiber. The medium considered in this research was the air and the results obtained indicate the feasibility of this approach and point out future developments.

ACS Style

G. E. Silva; Paulo Caldas; J. C. Santos. All-fiber sensor based on a metallic coated hybrid LPG-FBG structure for thermal characterization of materials. 23rd International Conference on Optical Fibre Sensors 2014, 9157, 1 .

AMA Style

G. E. Silva, Paulo Caldas, J. C. Santos. All-fiber sensor based on a metallic coated hybrid LPG-FBG structure for thermal characterization of materials. 23rd International Conference on Optical Fibre Sensors. 2014; 9157 ():1.

Chicago/Turabian Style

G. E. Silva; Paulo Caldas; J. C. Santos. 2014. "All-fiber sensor based on a metallic coated hybrid LPG-FBG structure for thermal characterization of materials." 23rd International Conference on Optical Fibre Sensors 9157, no. : 1.

Conference paper
Published: 02 June 2014 in OFS2014 23rd International Conference on Optical Fiber Sensors
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In this paper, we report the development of a reduced temperature sensitivity optical fiber sensor for refractive index measurement based on Superimposed Long-Period Gratings (SLPG) inscribed by the electric arc technique in standard fiber. The reduced sensitivity to temperature is achieved by calculation of the difference between resonance wavelengths of two guided cladding modes.

ACS Style

G. E. Silva; Paulo Caldas; J. C. Santos. Optical fiber refractive index sensor with reduced thermal sensitivity based on Superimposed Long-Period Gratings. OFS2014 23rd International Conference on Optical Fiber Sensors 2014, 9157, 1 .

AMA Style

G. E. Silva, Paulo Caldas, J. C. Santos. Optical fiber refractive index sensor with reduced thermal sensitivity based on Superimposed Long-Period Gratings. OFS2014 23rd International Conference on Optical Fiber Sensors. 2014; 9157 ():1.

Chicago/Turabian Style

G. E. Silva; Paulo Caldas; J. C. Santos. 2014. "Optical fiber refractive index sensor with reduced thermal sensitivity based on Superimposed Long-Period Gratings." OFS2014 23rd International Conference on Optical Fiber Sensors 9157, no. : 1.

Conference paper
Published: 02 June 2014 in OFS2014 23rd International Conference on Optical Fiber Sensors
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ACS Style

Renata F M Martins; Joao L Monteiro; Paulo Caldas; J. L. Santos; Gaspar Rego. Reflection-based phase-shifted long-period fiber grating for cryogenic temperature measurements. OFS2014 23rd International Conference on Optical Fiber Sensors 2014, 91571K -91571K-4.

AMA Style

Renata F M Martins, Joao L Monteiro, Paulo Caldas, J. L. Santos, Gaspar Rego. Reflection-based phase-shifted long-period fiber grating for cryogenic temperature measurements. OFS2014 23rd International Conference on Optical Fiber Sensors. 2014; ():91571K-91571K-4.

Chicago/Turabian Style

Renata F M Martins; Joao L Monteiro; Paulo Caldas; J. L. Santos; Gaspar Rego. 2014. "Reflection-based phase-shifted long-period fiber grating for cryogenic temperature measurements." OFS2014 23rd International Conference on Optical Fiber Sensors , no. : 91571K-91571K-4.

Review
Published: 18 June 2012 in Sensors
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A review of refractive index measurement based on different types of optical fiber sensor configurations and techniques is presented. It addresses the main developments in the area, with particular focus on results obtained at INESC Porto, Portugal. The optical fiber sensing structures studied include those based on Bragg and long period gratings, on micro-interferometers, on plasmonic effects in fibers and on multimode interference in a large spectrum of standard and microstructured optical fibers.

ACS Style

Pedro A. S. Jorge; Susana O. Silva; Carlos Gouveia; Paula Tafulo; Luis Coelho; Paulo Caldas; Diana Viegas; Gaspar Rego; José M. Baptista; José L. Santos; Orlando Frazão. Fiber Optic-Based Refractive Index Sensing at INESC Porto. Sensors 2012, 12, 8371 -8389.

AMA Style

Pedro A. S. Jorge, Susana O. Silva, Carlos Gouveia, Paula Tafulo, Luis Coelho, Paulo Caldas, Diana Viegas, Gaspar Rego, José M. Baptista, José L. Santos, Orlando Frazão. Fiber Optic-Based Refractive Index Sensing at INESC Porto. Sensors. 2012; 12 (6):8371-8389.

Chicago/Turabian Style

Pedro A. S. Jorge; Susana O. Silva; Carlos Gouveia; Paula Tafulo; Luis Coelho; Paulo Caldas; Diana Viegas; Gaspar Rego; José M. Baptista; José L. Santos; Orlando Frazão. 2012. "Fiber Optic-Based Refractive Index Sensing at INESC Porto." Sensors 12, no. 6: 8371-8389.

Book chapter
Published: 22 February 2012 in Fiber Optic Sensors
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ACS Style

Catarina Silva; Joo M. P. Coelho; Paulo Caldas; Pedro Jorge. Fibre Sensing System Based on Long-Period Gratings for Monitoring Aqueous Environments. Fiber Optic Sensors 2012, 1 .

AMA Style

Catarina Silva, Joo M. P. Coelho, Paulo Caldas, Pedro Jorge. Fibre Sensing System Based on Long-Period Gratings for Monitoring Aqueous Environments. Fiber Optic Sensors. 2012; ():1.

Chicago/Turabian Style

Catarina Silva; Joo M. P. Coelho; Paulo Caldas; Pedro Jorge. 2012. "Fibre Sensing System Based on Long-Period Gratings for Monitoring Aqueous Environments." Fiber Optic Sensors , no. : 1.

Journal article
Published: 09 June 2011 in Applied Optics
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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.

ACS Style

Paulo Caldas; Pedro Jorge; Gaspar Rego; Orlando Frazão; José Luís Santos; Luís Alberto Ferreira; Francisco Araújo. Fiber optic hot-wire flowmeter based on a metallic coated hybrid long period grating/fiber Bragg grating structure. Applied Optics 2011, 50, 2738 -2743.

AMA Style

Paulo Caldas, Pedro Jorge, Gaspar Rego, Orlando Frazão, José Luís Santos, Luís Alberto Ferreira, Francisco Araújo. Fiber optic hot-wire flowmeter based on a metallic coated hybrid long period grating/fiber Bragg grating structure. Applied Optics. 2011; 50 (17):2738-2743.

Chicago/Turabian Style

Paulo Caldas; Pedro Jorge; Gaspar Rego; Orlando Frazão; José Luís Santos; Luís Alberto Ferreira; Francisco Araújo. 2011. "Fiber optic hot-wire flowmeter based on a metallic coated hybrid long period grating/fiber Bragg grating structure." Applied Optics 50, no. 17: 2738-2743.

Conference paper
Published: 21 May 2011 in International Conference on Applications of Optics and Photonics
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This paper presents a comparative study of the behaviour of different kinds of optical fibre sensors in response to high temperatures. It compares the performance of regenerated fibre Bragg gratings (FBGs) written in hydrogen-loaded and non-loaded fibres with long period gratings (LPGs) written through the two different processes of ultraviolet (UV) irradiation and electrical arc discharges. This work shows the importance of the use of hydrogen-loaded fibres to achieve regenerated FBGs capable of withstanding high temperatures as high as 955°C. In addition, the results demonstrated that LPGs recorded by electric arc discharges have higher thermal resistance than LPGs written by UV radiation.© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

ACS Style

Luis B. Melo; Nara Ângelo; Nelia Aberto; Carlos Marques; José Monteiro; Gaspar Rego; Paulo Caldas; Rogério Nogueira. Comparative study of different parameters of fibre Bragg gratings and long period gratings sensors for high-temperature measurements. International Conference on Applications of Optics and Photonics 2011, 8001, 800123 -800123.

AMA Style

Luis B. Melo, Nara Ângelo, Nelia Aberto, Carlos Marques, José Monteiro, Gaspar Rego, Paulo Caldas, Rogério Nogueira. Comparative study of different parameters of fibre Bragg gratings and long period gratings sensors for high-temperature measurements. International Conference on Applications of Optics and Photonics. 2011; 8001 ():800123-800123.

Chicago/Turabian Style

Luis B. Melo; Nara Ângelo; Nelia Aberto; Carlos Marques; José Monteiro; Gaspar Rego; Paulo Caldas; Rogério Nogueira. 2011. "Comparative study of different parameters of fibre Bragg gratings and long period gratings sensors for high-temperature measurements." International Conference on Applications of Optics and Photonics 8001, no. : 800123-800123.

Journal article
Published: 20 April 2011 in Sensors and Actuators B: Chemical
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In this work is studied the response of optical fiber long period grating (LPG) to changes of the refractive index of the external media relatively to variations of wavelength and in transmission. The response of the LPG to refractive index greater and lesser than to cladding is investigated. A nanolayer was deposited onto the fiber to increase the sensitivity of the LPG to refractive index of the external media higher than cladding. The film modifies the rates of effective modes of cladding, thus improving the response of the changes in the refractive index of the external media higher than that in the refractive index of the cladding (ncl ≈ 1.457). The Langmuir–Blodgett technique was used for the deposition of the nanolayer.

ACS Style

Eliana Simões; I. Abe; João Oliveira; Orlando Frazão; Paulo Caldas; J.L. Pinto. Characterization of optical fiber long period grating refractometer with nanocoating. Sensors and Actuators B: Chemical 2011, 153, 335 -339.

AMA Style

Eliana Simões, I. Abe, João Oliveira, Orlando Frazão, Paulo Caldas, J.L. Pinto. Characterization of optical fiber long period grating refractometer with nanocoating. Sensors and Actuators B: Chemical. 2011; 153 (2):335-339.

Chicago/Turabian Style

Eliana Simões; I. Abe; João Oliveira; Orlando Frazão; Paulo Caldas; J.L. Pinto. 2011. "Characterization of optical fiber long period grating refractometer with nanocoating." Sensors and Actuators B: Chemical 153, no. 2: 335-339.

Short communication
Published: 15 November 2010 in Talanta
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The analysis of the quality of food oils is of paramount importance, because the degradation of oils can lead to formation of harmful substances to the human organism. With the increase of the degradation of oils an increase of its refractive index occurs. The objective of this work is to develop and to characterize optical fiber refractometers sensitive to variations of refractive index of food oil samples. The optical fiber refractometers thanks to the intrinsic characteristics make them suitable for monitoring the quality of frying oils. They possess the advantages to require small volumes of sample for analysis, do not contaminate the sample, and supply the response in real time. In this work a long period grating (LPG) as refractometer is used because of their sensitivity to refractive index of the external media: degraded and not degraded frying oil samples. The oil samples had been characterized by the analysis of total polar components. The refractive index of oil is above 1.47, this region the LPG does not show enough sensitivity, a nanolayer of an organic material was coated onto the fiber. Using the Langmuir–Blodgett technique the response of LPG is modified according to the refractive index and thickness of the film. The deposition of the film modifies the rates effective modes of cladding, thus improving the response of the changes in the refractive index of the external media higher than that the refractive index of the cladding (n = 1.457).

ACS Style

I. Abe; João Oliveira; Eliana Simões; Paulo Caldas; Orlando Frazão. Monitoring the quality of frying oils using a nanolayer coated optical fiber refractometer. Talanta 2010, 83, 291 -293.

AMA Style

I. Abe, João Oliveira, Eliana Simões, Paulo Caldas, Orlando Frazão. Monitoring the quality of frying oils using a nanolayer coated optical fiber refractometer. Talanta. 2010; 83 (1):291-293.

Chicago/Turabian Style

I. Abe; João Oliveira; Eliana Simões; Paulo Caldas; Orlando Frazão. 2010. "Monitoring the quality of frying oils using a nanolayer coated optical fiber refractometer." Talanta 83, no. 1: 291-293.

Journal article
Published: 28 October 2010 in IEEE Photonics Technology Letters
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Optical coherence tomography (OCT) imaging at the 1060-nm region proved to be a successful alternative in ophthalmology not only for resolving intraretinal layers, but also for enabling sufficient penetration to monitor the subretinal vasculature in the choroid when compared to most commonly used OCT imaging systems at the 800-nm region. To encourage further clinical research at this particular wavelength, we have developed a compact fiber-optic source based on amplified spontaneous emission (ASE) centered at 1060 nm with 70-nm spectral bandwidth at full-width at half-maximum and output power 20 mW. Our approach is based on a combination of slightly shifted ASE emission spectra from a combination of Neodymium- and Ytterbium-doped fibers. Spectral shaping and power optimization have been achieved using in-fiber filtering schemes. We have tested the performance of the source in an OCT system optimized for this wavelength.

ACS Style

I. Trifanov; P. Caldas; L. Neagu; R. Romero; M. O. Berendt; J. A. R. Salcedo; A. Gh. Podoleanu; António B. Lobo Ribeiro. Combined Neodymium–Ytterbium-Doped ASE Fiber-Optic Source for Optical Coherence Tomography Applications. IEEE Photonics Technology Letters 2010, 23, 21 -23.

AMA Style

I. Trifanov, P. Caldas, L. Neagu, R. Romero, M. O. Berendt, J. A. R. Salcedo, A. Gh. Podoleanu, António B. Lobo Ribeiro. Combined Neodymium–Ytterbium-Doped ASE Fiber-Optic Source for Optical Coherence Tomography Applications. IEEE Photonics Technology Letters. 2010; 23 (1):21-23.

Chicago/Turabian Style

I. Trifanov; P. Caldas; L. Neagu; R. Romero; M. O. Berendt; J. A. R. Salcedo; A. Gh. Podoleanu; António B. Lobo Ribeiro. 2010. "Combined Neodymium–Ytterbium-Doped ASE Fiber-Optic Source for Optical Coherence Tomography Applications." IEEE Photonics Technology Letters 23, no. 1: 21-23.