Determination of phase noise spectra in optoelectronic microwave oscillators: a Langevin approach

We introduce a stochastic model for the determination of phase noise in optoelectronic oscillators. After a short overview of the main results for the phase diffusion approach in autonomous oscillators, an extension is proposed for the case of optoelectronic oscillators where the microwave is a limit-cycle originated from a bifurcation induced by nonlinearity and time-delay. This Langevin approach based on stochastic calculus is also successfully confronted with experimental measurements.Comment: 18 pages, 7 figures, 11 references. Submitted to IEEE J. of Quantum Electronics, May 200

Complex photonic nonlinear delay dynamics for high performance signal and information processing

International audienceOptoelectronic delayed feedback loops can provide a wide variety of dynamical motions, thanks to their infinite dimensional phase space. When implemented with Telecom grade components, they additionally provide broadband operation, particularly suited for high speed signal and information processing. On the basis on experimental illustration, we will introduce the fundamental nonlinear dynamical properties of photonic delayed feedback systems, from their stable fixed point operation to their high dimensional complex chaotic oscillations, through periodic oscillations. Each of these particular solution will then be further developed to demonstrate advanced information and signal processing capabilities, from secure optical chaos communications at 10Gb/s, to ultra-fast million word per second recognition through neuromorphic computing, through microwave high spectral purity oscillations for radar applications

Photonic nonlinear transient computing with multiple-delay wavelength dynamics

International audienceWe report on the experimental demonstration of a hybrid optoelectronic neuromorphic computer based on a complex nonlinear wavelength dynamics including multiple delayed feedbacks with randomly defined weights. This neuromorphic approach is based on a new paradigm of a brain-inspired computational unit, intrinsically differing from Turing machines. This recent paradigm consists in expanding the input information to be processed into a higher dimensional phase space, through the nonlinear transient response of a complex dynamics excited by the input information. The computed output is then extracted via a linear separation of the transient trajectory in the complex phase space. The hyperplane separation is derived from a learning phase consisting of the resolution of a regression problem. The processing capability originates from the nonlinear transient, resulting in nonlinear transient computing. The computational performance is successfully evaluated on a standard benchmark test, namely, a spoken digit recognition task

Investigation of the complex dynamics and regime control in Pierce diode with the delay feedback

In this paper the dynamics of Pierce diode with overcritical current under the influence of delay feedback is investigated. The system without feedback demonstrates complex behaviour including chaotic regimes. The possibility of oscillation regime control depending on the delay feedback parameter values is shown. Also the paper describes construction of a finite-dimensional model of electron beam behaviour, which is based on the Galerkin approximation by linear modes expansion. The dynamics of the model is close to the one given by the distributed model.Comment: 18 pages, 6 figures, published in Int. J. Electronics. 91, 1 (2004) 1-1

Mismatch-Induced Bit Error Rate in Optical Chaos Communications Using Semiconductor Lasers With Electrooptical Feedback

8 pages, 8 figures.We analyze the influence of parameter mismatch between emitter and receiver systems on the bit error rate of an optical chaos communication scheme. Intensity hyperchaos is generated in the system by semiconductor lasers with electro-optical feedback. We find analytical predictions for the dependence of the bit error rate with the amplitude of the various mismatches and the statistical properties of the hyperchaotic carrier. A good concordance is found with numerical and experimental results.This work was supported in part by the European Commission through the research project OCCULT under Contract IST-2000-29683, in part by the the MEC (Spain) and FEDER under Projects FIS2004-00953 (CONOCE2), BFM2001-0341-C02-02 (SINFIBIO), and TIC2001-4572-E, and in part by a research grant from the Govern de les Illes Balears.Peer reviewe

Temporal dynamics of Kerr frequency combs in whispering-gallery mode resonators

International audienceBased on a modal description of the evolution of the mode's amplitude in a whispering-gallery mode resonator, we numerically study the generation of Kerr combs. We show that a stable primary comb appear for pump power slightly above threshold, enabling potential applications in metrology. For high input power however, chaotic signals are observed

On phase locking phenomena in Kerr combs

International audienceBased on a modal description of the evolution Kerr combs in a whispering-gallery mode resonator, we numerically investigate the phase bhavior of the different spectral lines of the spectrum. We show that a stable phase relation exists between adjacent modes in primary combs. This result is of great interest for metrological applications where one phase noise is an issue. For high input power however, chaotic signals are observed

Effect of fiber dispersion on broadband chaos communications implemented by electro-optic nonlinear delay phase dynamics

We investigate theoretically and experimentally the detrimental e ect of ber dispersion on the synchroniza- tion of an optoelectronic phase chaos cryptosystem. We evaluate the root-mean square synchronization error and the cancellation spectra between the emitter and the re- ceiver in order to characterize the quality of the optical ber communication link. These two indicators explicitly show in temporal and spectral domain how ber dispersion does negatively a ect the phase chaos cancellation at the re- ceiver stage. We demonstrate that the dispersion manage- ment techniques used in conventional optical ber networks, such as dispersion-compensating modules/ bers or disper- sion shifted bers, are also e cient to strongly reduce the detrimental e ects of ber propagation in phase chaos com- munications. This compatibility therefore opens the way to a successful integration of more than 10-Gb/s phase chaos communications systems in existing networks, even when the ber link spans over more than 100 km.Peer reviewe

Génotypage du virus de la rougeole par PCR en temps réel: Cas des souches virales isolées au Maroc pendant la saison 2004-2005

Le génotypage du virus de la rougeole (VR) est un outil important dans la surveillance de la rougeole. Il permet d’identifier l’origine du virus, ses voies de transmission et d’évaluer les programmes de vaccination. Vu l’importance du génotypage du VR dans le programme de l’élimination de la rougeole, une technique rapide a été développée. Cette technique se base sur l’identification des génotypes par PCR en temps réel, les différents génotypes sont distingués par leur température de fusion (Tm). Cette méthode constitue une alternative efficace pour l’investigation des épidémies de rougeole dans les pays en phase d’élimination.Les souches du virus de la rougeole isolées pendant la saison 2004-2005 ont été identifiées par PCR en temps réel puis confirmées par le séquençage des gènes H et N. cette étude, a permis de montrer une rapide diversification des génotypes qui circulent au Maroc. Parmi ces génotypes, certains sont importés de l’Afrique de l’Ouest et de l’Europe, d’autres correspondent à la souche autochtone. Ces résultats montrent la nécessité de renforcer la couverture vaccinale et d’introduire une nouvelle stratégie de vaccination dans le but d’éliminer la maladie

EXTERNALISATION DE LA FONCTION COMPTABLE : RISQUE ET ENJEUX DU CÔTÉ PRESTATAIRE

L’objectif principal de cette étude est d’analyser les risques et enjeux liés à l’exécution d’uncontrat d’externalisation. En se basant sur l’étude de cas d’un cabinet ayant un porte feuillesde 37 dossiers d’entreprises, cette étude propose aux cabinets d’expertises comptables desmesures permettant de mieux gérer les risques liés à la pratique de l’externalisation de lafonction comptable chez le prestataire