Eric A. M. Fagotto

Optical amplitude multiplexing through four-wave mixing in optical fibers

We propose a new optical amplitude multiplexing technique that consists of merging two wavelength multiplexed on-off keying (OOK) signals into a single quaternary amplitude shift keying signal. This technique is based on four-wave mixing in a single-mode optical fiber and requires power offset from the OOK signals. Simulation results indicate that the multiplexing may be performed between signals of the same or different bit rates. As a consequence, the proposed technique may be used not only for increasing spectral efficiency but also for optical labeling.

Quaternary optical packets generated by fiber four-wave mixing

Recent work suggests that fiber four-wave mixing may be used to merge two wavelength multiplexed binary channels into a single quaternary signal. In this letter, we investigate the application of this technique to the optical packets generation considering that a 10-Gb/s payload is optically multiplexed to a 2.5-Gb/s label. Computer simulations are used to analyze the propagation of the generated quaternary optical packet in the dominance of amplified spontaneous emission noise. Results suggest that the optical packet may be propagated through metropolitan area networks length scales and that an average power around 0 dBm should be used to minimize the packet bit-error rate.

All-optical cryptography through spectral amplitude and delay encoding

All-optical data encryption is a promising technology that could lead communication systems to an unprecedented degree of security. In this paper we use computer simulations to systematically investigate a new all-optical cryptography technique that is bit-rate independent and transparent to modulation formats. Encryption encompasses signal spectral slicing followed by two encoding stages that impose different attenuations and delays to each of the spectral slices. We analyze the quality of the encoded signal by evaluating its bit error rate (BER) performance. Results indicate that such BER may achieve 45 and 28%, respectively, for input non-return-to-zero on-off keying (NRZ-OOK) and differential quadrature phase-shift keying (DQPSK) signals. At the receiver side, results suggest that signals may be properly decoded after propagation distances that are compatible with those utilized in metropolitan area networks. The robustness of the technique against waveform analysis and brute force attacks is also approached.

Ultra-broadband Two-pump Optical Parametric Amplifier In Tellurite Waveguides With Engineered Dispersion

The capacity of communication networks may be significantly improved by simply enhancing the optical amplifier bandwidth. This paper presents a numerical investigation of an ultra-broadband, low-ripple, two-pump-optical parametric amplifier (2P-OPA) that employs a tellurite glass buried-channel type nano-waveguide as nonlinear medium. The nano-waveguide was designed as a 25-cm-long Archimedean spiral that occupies a footprint of only ~2.5 mm2, with a ~0.7 μm2 effective cross section. Its zero-dispersion wavelength is ~1550 nm, the nonlinear coefficient is ~3000 W-1 km-1 , and the attenuation coefficient is ~0.5 dB/m (1100 to 1900 nm). Simulations suggest a 2P-OPA based on such waveguide will be able to amplify 243 QPSK input channels modulated at 56 Gbps over 102 nm bandwidth, over metropolitan area network scales.

A new all-optical cryptography technique applied to WDM-compatible DPSK signals

We investigate the application of a new all-optical cryptography technique to wavelength division multiplexing (WDM)-compatible differential phase-shift keying (DPSK) signals. The technique uses current optical band-pass optical filters with narrow bandwidths to divide a given input WDM-compatible signal into several spectral slices, which are submitted to two cryptographic key stages. The first one impresses amplitude encoding, whereas the second imposes delay variations to each spectral slice. The technique performance is assessed by evaluating the encrypted and decrypted signals bit error rates. Computer simulations suggest that encrypted DPSK signals may be properly recovered even after being propagated through typical metropolitan area network distances.

All-optical phase and delay spectral encoding of signals with advanced modulation formats

We have investigated the application of a new all-optical cryptography technique to advanced modulation signals. Such technique is based on two-stage encoding scheme applied on narrowband spectral slices within composite dense wavelength division multiplexing (DWDM) signals. The first encoding stage implements spectral phase altering, while the second one imposes the cyphering delay to each spectral slice. Simulation results indicate that this coding technique can be successfully applied on advanced coded modulation formats with channel bit rates of 200 Gbps over metropolitan area networks.

High Availability: A Approach with DNS and Reverse Proxy in Multi-Cloud

In spite of Cloud Computing services seem to be very attractive as an alternative to traditional on-premise data centers, there is still some concern about the providers availability. This article describes a solution that implements high availability Multi-Cloud through the distribution of DNS access and the use of reverse proxy. The results obtained, by means of simulations indicate that, in principle, one can obtain an arbitrary Multi-Cloud availability, by using Clouds of lower availability. Specifically, it was shown that, from two Clouds of 99.43% and 99.49% availability one can obtain a 99.9971% Multi-Cloud system. It is also shown that, in this particular case, the Multi-Cloud system costs 34% less than the solution with a single Cloud.

Network performance of optical parametric amplifiers based on tellurite waveguides

Optical parametric amplifiers (OPA) built on glass waveguides are tuneable devices that may be implemented as part of photonic integrated circuits. In this paper, we investigate the performance of recently proposed tellurite OPAs in transparent optical networks (TONs). The dispersion of these OPAs was engineered to provide high gain (∼18 dB) and low ripple (∼4.5 dB) over a bandwidth that is around three times wider than that offered by commercially available Erbium-doped fibre amplifiers. In particular, we analyse a scenario where wavelength division multiplexed (WDM) signals are transmitted through a TON equipped with tellurite two-pump OPAs (2P-OPA) to compensate the link transmission loss. Computer simulations are used to evaluate the influence of 2P-OPA crosstalk on the bit error rate (BER), as well as on the reach, of 243 quadrature phase-shift keying (QPSK) 56 Gbps signals that span over ∼100 nm. Results indicate that by setting the launched optical power to −29 dBm per channel successful transmission in TONs with diameters as large as 1000 km can be achieved.

Compact Narrowband Optical Filter Based on Ring Ressonators in Silicon Photonics

In this paper, we present and discuss a new proposal for narrowband optical band pass filters based on asymmetric ring resonators in silicon. We carried out our investigation, by means of analytical and numerical calculations, to find out the best ring radii ratio and spacing between the rings in order to achieve narrow band filtering. As result, we devised a three-ring structure that performs as an 11.7 GHz optical band pass filter and, then, by cascading three structures of this, we obtained a 7.1 GHz optical band pass filter. Furthermore, this sort of filter would occupy a 20 μm per 28 μm area, which is considerably smaller than the correspondent state-of-the-art reported in literature until now. We also demonstrated this filter is suitable to mitigate signal-fading effects in Radio over Fiber (RoF) links. Our results indicate that, by using the proposed filters, the maximum propagation distance for RoF links could be increased from 4 km to 40 km. Since this new filter combines reduced dimensions, it has great potential to integration with other opto-electronics components into a silicon photonics circuit.

Diagnóstico e tratamento de incidentes na rede de computadores

Atualmente as redes de computadores no âmbito empresarial possuem sistemas e equipamentos essenciais ao negocio sendo que qualquer parada nao planejada acarretara em diversos problemas e prejuizos, comprometendo o resultado e desempenho produtivo das companhias (HEEGAARD, 2009: 1215). Esforcos na literatura concentram-se em potencializar a disponibilidade da rede e dos servicos nela contidos, bem como prover um rapido reestabelecimento da mesma em caso de falhas (WU, 2012: 421) (ORLOWSKI, 2010: 277) (YOUNIS, 2009:64). Neste trabalho e apresentado um metodo para a classificacao, diagnostico e tratamento dos incidentes a partir de processos para rastreamento de problemas na rede, identificacao dos ambientes criticos ao negocio do cliente. Contempla o acompanhamento executivo em crises decorrentes de incidentes em tais ambientes e uma proposta de fluxo para uma estrutura de atendimento que aplique todos esses processos integrados com as melhores praticas do ETOM-ITIL. Full Paper PDF: http://www.contecsi.fea.usp.br/envio/11contecsi-files/papers/842/submission/director/842-2505-1-DR.pdf