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Publications

Publications by Henrique Salgado

2004

In situ temperature measurement of an optical fiber submitted to electric arc discharges

Authors
Rego, G; Santos, LMNBF; Schroder, B; Marques, PVS; Santos, JL; Salgado, HM;

Publication
IEEE PHOTONICS TECHNOLOGY LETTERS

Abstract
Type S thermocouples were assembled in situ by applying high intensity electric are discharges to the contact junction of two platinum (Pt) and Pt-10% rhodium (Pt-10% Rh) wires, inserted on a silica capillary. The electrically insulated thermocouples built in this way were afterwards employed to estimate the temperature of an optical fiber subjected to arc discharges. For typical values of the arc discharge parameters used to arc-induce long-period fiber gratings (electric current I = 9 mA and arc duration t = 1 s), a capillary peak temperature value of 1420 degreesC +/- 400 degreesC was obtained by extrapolation of the experimental data for the limit situation of having a thermocouple with negligible diameter. The temperature profiles in the capillary and in an optical fiber were calculated based on a heat transfer model implemented by a finite element algorithm and fitted to the experimental temperature distribution in the Pt and Pt-10% Rh wires. The correspondent peak temperatures computed for the capillary and for the fiber were 1450 degreesC and 1320 degreesC, respectively. A good agreement between the capillary temperature values determined graphically and numerically was obtained.

2009

Assessment of Parallel Equalizer/Phase Estimation Algorithms in Coherent Optical Systems

Authors
Pessoa, LM; Salgado, HM; Darwazeh, I;

Publication
2009 DIGEST OF THE LEOS SUMMER TOPICAL MEETINGS

Abstract
The options to implement a coherent optical system employing a phase estimation algorithm combined with adaptive linear equalization are investigated. Several carrier phase estimator strategies are discussed, in terms of parallelization, performance and implementation complexity.

2008

Joint Mitigation of Optical Impairments and Phase Estimation in Coherent Optical Systems

Authors
Pessoa, LM; Salgado, HM; Darwazeh, I;

Publication
2008 DIGEST OF THE LEOS SUMMER TOPICAL MEETINGS

Abstract
The electrical compensation of chromatic dispersion (CD) and polarization mode dispersion (PMD) in a coherent optical system exploiting polarization multiplexing is discussed in this paper. The benefits of combining a phase estimation algorithm with a decision directed least-mean-square equalizer in a feedback configuration is reported.

2011

Compact Printed Monopole Antenna With Chip Inductor for WLAN

Authors
Luo, Q; Pereira, JR; Salgado, HM;

Publication
IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS

Abstract
One compact printed monopole antenna with a chip inductor for dual-band WLAN is presented. The proposed antenna has a two-armed structure and an electrically small size. The equivalent circuit structure of the chip inductor is studied and a simplified circuit structure is proposed. This simplified circuit structure was introduced into the electromagnetic (EM) simulation model by assigning a boundary condition, and the experimental results show that with this model, the simulation can provide an accurate prediction of the antenna radiation performance. The measurement results show that the proposed monopole antenna has a VSWR 2: 1 bandwidth over 2.41-2.49 and 5.2-5.6 GHz with omnidirectional radiation patterns. The simulation results suggest that the proposed antenna has a directivity around 1.5 dB at both bands with relatively high radiation efficiency. The antenna is designed and optimized by using Ansoft HFSS.

2009

Fractal monopole antenna for WLAN USB dongle

Authors
Luo, Q; Pereira, JR; Salgado, HM;

Publication
Loughborough Antennas and Propagation Conference, LAPC 2009 - Conference Proceedings

Abstract
This article presents the design and fabrication of a simple printed fractal monopole antenna for WLAN USB dongle applications. The proposed antenna uses the combination of meander line and fractal geometry, which is very simple and easy to fabricate, to achieve a multiband operation characteristic. The parameters of this antenna were optimized through numerical simulations in Ansoft HFSS, after which the antenna has been fabricated and characterized. The measurement results show that the proposed antenna has a -10 dB return loss bandwidth of 2.22 to 2.52 GHz and 5.03 to 5.84 GHz, which covers the entire required band for WLAN 802.11a/b/g standards. Moreover, from the simulation results, it is also observed that this proposed antenna exhibits constant gain of 1.8 dBi with 95% radiation efficiency in the lower band and 2.4 dBi with 94% radiation efficiency in the upper band, respectively. ©2009 IEEE.

2006

Interrogation of a fiber Bragg grating using a mechanically induced long-period fiber grating

Authors
Rego, GM; Salgado, HM; Santos, JL;

Publication
IEEE SENSORS JOURNAL

Abstract
A fiber-sensing scheme with controlled sensitivity comprising a fiber Bragg grating (FBG) and a mechanically induced long-period fiber grating (MLPFG) is presented. The FBG was written by exposing the fiber to 248-nm UV laser radiation such that the Bragg wavelength is localized on the slope of a resonant band of a mechanical grating, which was produced by winding a nylon string around a fiber/grooved tube set. The strength of that resonant band was altered by applying loads to the MLPFG. For different loads, the FBG was submitted to strain values of up to 2200 mu epsilon, in steps of 200 mu epsilon, during which the Bragg wavelength and the respective transmitted peak power through the MLPFG were recorded. It was demonstrated that by applying a weight with a value of 0.78 kg to the MLPFG, the sensitivity of the FBG interrogation technique to strain variations increased from 2.23 (without load) to 3.20 pW/mu epsilon.

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