Search results for "Length"
showing 10 items of 2188 documents
Variable Length Markov Chains, Persistent Random Walks: a close encounter
2020
This is the story of the encounter between two worlds: the world of random walks and the world of Variable Length Markov Chains (VLMC). The meeting point turns around the semi-Markov property of underlying processes.
Persistent random walks, variable length Markov chains and piecewise deterministic Markov processes *
2013
A classical random walk $(S_t, t\in\mathbb{N})$ is defined by $S_t:=\displaystyle\sum_{n=0}^t X_n$, where $(X_n)$ are i.i.d. When the increments $(X_n)_{n\in\mathbb{N}}$ are a one-order Markov chain, a short memory is introduced in the dynamics of $(S_t)$. This so-called "persistent" random walk is nolonger Markovian and, under suitable conditions, the rescaled process converges towards the integrated telegraph noise (ITN) as the time-scale and space-scale parameters tend to zero (see Herrmann and Vallois, 2010; Tapiero-Vallois, Tapiero-Vallois2}). The ITN process is effectively non-Markovian too. The aim is to consider persistent random walks $(S_t)$ whose increments are Markov chains with…
Mid-infrared strong spectral broadening in microstructured tapered chalcogenide AsSe fiber
2012
We report on the generation of a supercontinuum in a chalcogenide microstructured tapered fiber. The suspended core diameter of the fiber is reduced from 5.5 μm to 0.8 μm in the waist of the tapered region. The zero dispersion wavelength is below 2 μm in the tapered region. To pump the fiber, we use a modelocked laser of 4 ps, with a central wavelength of 1960 nm. With only 150 W peak power in the fiber a supercontinuum is generated from 1300 to 2600 nm taking the supercontinuum wavelength edge at -30 dB from the continuum.
Titanium Dioxide Waveguides for Data Transmissions at 1.55 µm and 1.98 µm
2017
International audience; We demonstrate error free transmissions of 10 Gbps signals in titanium dioxide waveguides at wavelengths of 1.55 or 2 µm. An efficient coupling of light is achieved thanks to metal grating couplers and we have checked that the component could be used with standard CWDM SFP+ devices.
Dielectric-loaded plasmonic waveguide-ring resonators
2009
International audience; Using near-field microscopy, the performance of dielectric-loaded plasmonic waveguide-ring resonators (WRRs) operating at telecom wavelengths is investigated for various waveguide-ring separations. It is demonstrated that compact ( footprint similar to 150 mu m(2)) and efficient ( extinction ratio similar to 13 dB) WRR-based filters can be realized using UV-lithography. The WRR wavelength responses measured and calculated using the effective-index method are found in good agreement. (c) 2009 Optical Society of America
Mid-infrared supercontinuum generation in suspended-core chalcogenide and tellurite optical fibers
2013
Summary form only given. The generation of optical supercontinua in the mid-infrared region and especially their expansion beyond the intrinsic limit dictated by fused silica is currently a subject of high interest. Tellurite and chalcogenide glasses have serious advantages because of their wide transmittance window which can reach more than 10 μm while the Kerr nonlinearity can be 500 times stronger than fused silica. These different features make them serious candidates for broad mid-infrared supercontinuum generation. For example, supercontinuum as broad as 4000-nm bandwidth has been generated in a sub-cm long Tellurite microstructured fiber by Domachuk et al. in ref. [1] by means of a f…
Simultaneous 2R regeneration of WDM signals in a single optical fibre
2009
Two experimental implementations of amplitude regeneration of WDM signals based on self-phase modulation (SPM) in optical fibres are discussed. The two examples differ in their approach of mitigation of inter-channel nonlinearities.
New concepts based on nonlinear polarization effects and Raman amplification in optical fibers
2009
We report a theoretical analysis and experimental demonstration of a polarization attraction process at telecommunication wavelengths in isotropic optical fibers. The combined effects of polarization attraction and Raman amplification are also presented.
Shallow water rogue waves in nonlinear optical fibers
2013
The dynamics of extreme waves, often known as freak or rogue waves (RW), is presently a subject of intensive research. In oceanography, RW are mostly known as a sudden deep-water event which is responsible for ship wreakages and can be modeled by the 1D Nonlinear Schrodinger Equation (NLSE). In this framework, an ideal testbed is provided by optical pulse propagation in nonlinear optical fibers: extreme solitary wave emissions during supercontinuum generation or the first experimental observation of the Peregrine solitons have indeed been carried out exploiting the modulation instability occuring in fibers with anomalous dispersion.
A near-field actuated optical nanocavity
2008
International audience; We demonstrate here that switching and tuning of a nanocavity resonance can be achieved by approaching a sub-micrometer tip inside its evanescent near-field. The resonance energy is tuned over a wide spectral range (Δλ/λ~10-3) without significant deterioration of the cavity peak-transmittance and of the resonance linewidth. Such a result is achieved by taking benefits from a weak tip-cavity interaction regime in which the tip behaves as a pure optical path length modulator.