Institute Telecomunicacaes

Lisbon, Portugal

Institute Telecomunicacaes

Lisbon, Portugal
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Lunca E.,Technical University Gheorghe Asachi | Damian C.,Technical University Gheorghe Asachi | Petrisor D.,Technical University Gheorghe Asachi | Postolache O.,Institute Telecomunicacaes
EPE 2012 - Proceedings of the 2012 International Conference and Exposition on Electrical and Power Engineering | Year: 2012

The digital potentiometers are flexible devices allowing many of the applications of the mechanical trimming to be replaced by a solid state solution. In this paper, we address issues related to the use of the digital potentiometers in the active filter design, in order to implement programmable analog functions such as controlling the corner frequency and filter type. Also, we propose here a simple interfacing solution that allows for quickly configuring not only programmable filters, but other common circuits employing I2C digital potentiometers. © 2012 IEEE.

Sousa A.O.P.,Institute TelecomunicacAes | Sousa A.O.P.,University of Aveiro | Marques C.A.F.,Institute TelecomunicacAes | Nogueira R.,Institute TelecomunicacAes | And 4 more authors.
Microwave and Optical Technology Letters | Year: 2013

This work presents a technique based on the application of a high birefringent (Hi-Bi) fiber Bragg grating (FBG) to monitor the optical signal to noise ratio (OSNR) of an optical channel.A Hi-Bi FBG produces reflection at two different spectral bands depending on the polarization of the incoming signal. The OSNR can be determined by decomposing, for a data channel, the polarized signal information and the depolarized noise. This work gathers the simulation and experimental results for a single channel system continuous wave signal and modulated at 10 Gb s-1. The results for a multichannel system are also presented. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:6-9, 2013; View this article online at DOI 10.1002/mop.27228 Copyright © 2012 Wiley Periodicals, Inc.

Ganhao F.,New University of Lisbon | Ganhao F.,Institute Telecomunicacaes | Cunha B.,New University of Lisbon | Bernardo L.,New University of Lisbon | And 5 more authors.
2014 International Conference on Telecommunications and Multimedia, TEMU 2014 | Year: 2014

Current wireless communication systems rely on the assumptions of the Nyquist theorem. Faster-Than-Nyquist (FTN) assumes that a bandwidth below the Nyquist bandwidth can be used with minimum loss, however the existing receivers are too complex. Single Carrier with Frequency-Domain Equalization (SC-FDE) has been proposed to handle multipath dispersive broadband channels, however the uplink of SC-FDE can be severely affected by deep-fades and/or poor channel conditions. To cope with such difficulties Diversity Combining (DC) Hybrid ARQ is a viable technique, since it combines the several packet copies sent by a Mobile Terminal to create reliable packet symbols at the receiver. This paper proposes a simple SC-FDE Packet Error Rate analytical model using FTN signaling, based on the Iterative Block with Decision Feedback Equalization technique, which achieves a performance similar to Nyquist signaling. © 2014 IEEE.

Oliveira R.,Institute Telecomunicacaes | Bilro L.,Institute Telecomunicacaes | Heidarialamdarloo J.,Institute Telecomunicacaes | Nogueira R.,Institute Telecomunicacaes
24th International Conference on Plastic Optical Fibers, POF 2015 - Conference Proceedings | Year: 2015

We report the inscription and characterization of Bragg gratings in different polymer optical fibers. The inscription was done with a 248 nm UV radiation from a KrF laser, conventionally used for the inscription of silica FBGs. The polymer fiber Bragg gratings were written in a few seconds, due the strong absorption and high photosensitivity of PMMA under deeper wavelengths. This work provides a step forward related with the time needed to inscribe PFBGs. After the inscription, the Bragg gratings were characterized to strain, temperature, pressure and humidity, revealing sensitivities closer to the ones reported for PFBGs inscribed with 325 nm UV radiation.

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