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Raman Amplifiers for Use in WDM Systems
D. B. M. Pereira; A. L. J. Teixeira; M. J. N. Lima; P. S. B. André; H. C. C. Fernandes; J. R. Ferreira da RochaIn this paper Raman Amplifiers (RAs) for Wavelength Division Multiplexed (WDM) fiber optic systems are analysed. We start by explaining the physical principles of this kind of amplification are explained, and the principal characteristics and advantages of using these amplifiers are enumerated.The technique of multiple pumping (MP) is studied aiming to obtain broadband amplifiers w...
Ferramenta de Simulação para Análise Espectral de Redes de Bragg
Rogério P. Dionísio; Mário J. Lima; J. R. Ferreira da Rocha; J. L. Pinto; António J. TeixeiraFiber Bragg gratings are becoming important components for optical communication networks, allowing many operations to be realized without the need of conversion between electrical and optical domain. This paper presents a simulation and design tool for spectral characterization of Bragg gratings, based on Matlab, together with a graphical user interface created fromGUIDE toolbox, ...
A New Scheme for OCDMA using 2D Codes and Differential Detection
Paulo Santos; Rogério N. Nogueira; Paulo André; J. R. Ferreira da Rocha; António J. TeixeiraA new optical system with wavelengthencoding/time-spreading Optical Code Division Multiple Access (O-CDMA) is proposed. Using orthogonal polarizations we can have a simple encoding and decoding of two independent channels and achieve differential detection.The resulting system has a constant null decision threshold and therefore a superior performance when compared with a system with di...
Wideband Erbium-Doped Fiber Amplifier System Design Limitations due to Cband Si...
D. B. M. Pereira; A. L. J. Teixeira; M. J. N. Lima; P. S. B. André; J. R. Ferreira da RochaIn this paper we observe experimentally the effects of C-band pump light in the performances of an Lband Erbium-Doped Fiber Amplifier (EDFA). An amplifier for C+L-bands in a parallel configuration of two EDFAs is designed, and the inherent implications in its application to optical fiber communications systems. A new configuration is presented for decreasing the signal gain depende...
Realização em tecnologia monolítica de Arsenieto de Gálio (GaAs MMIC) de amplif...
António L.J. Teixeira; Mário J. N. Lima; J. Nuno Matos; Paulo Monteiro; J. R. Ferreira da RochaNowadays the clock recovery circuits used for frequencies up to 10 Gbit/s use open-loop structures. The band-pass filters used on these structures are implemented with dielectric resonators (DR). This kind of filters introduce spurious modes that degradate the characteristics of the recovered clock signal. So, the clock amplification stage is required not only to provide the desired clock signal levels, but als...
Redes de Bragg para filtragem em sistemas WDM
Mário J. N. Lima; António L. J. Teixeira; J. R. Ferreira da RochaIn this contribution it is demonstrated the efficiency of apodized Bragg gratings, with negative variation of the refractive index, as optical filters in wavelength division multiplexing (WDM) systems, acting simultaneously as demultiplexers and dispersion compensators. Using a negative apodized Bragg grating, with a Gaussian profile, it is possible to demultiplex a 160 Gbit/s ...
Thermally Tunable Bragg Grating Filtrers for Wavelength-Multiplexed Systems
M. J. N. Lima; O. Frazão; A. L. J. Teixeira; P. S. B. André; J. R. Ferreira da RochaIn this contribution we compare the thermal tuning capabilities of two type I gratings, considering an unloaded and a hydrogen-loaded fiber, and a type IIa grating. We further study their responses stability with temperature, analyzing their potential as optical filters in wavelength division multiplexing systems. We conclude that all of them have similar tuning efficiencies, howev...
Impact of Non-zero Extinction Ratio on Optically Pre-amplified Receivers
L. F. Botelho Ribeiro; J. R. Ferreira da Rocha; J. Lemos PintoIn practical optical communication systems, the transmitter laser is polarised with a finite current. A given optical power plateau is, thus, observed at the receiver. This contribution includes this phenomenon in an analytical formulation for statistical description of a optically preamplified direct-detection system. ; Em sistemas práticos de comunicações Ó...
Tunable L-band erbium-doped fibre ring laser by means of induced cavity loss us...
M. Melo; O. Frazão; A. L. J. Teixeira; L. A. Gomes; J.R. Ferreira da Rocha; H. M. SalgadoIn this paper, we present a continuous-wave tunable fibre ring laser operating in the L-band. A bi-directional pumped L-band erbium-doped fibre amplifier provides gain to the loop. Tunability is achieved by bending a single-mode fibre taper using a micrometer drive, controlling in this way the spectral cavity losses. Laser emission is achieved between 1587 and 1606 nm, and low variation of the output laser powe...
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