Search results for "Dispersion"

Fully automatic simultaneous fiber grating amplitude and group delay characterization

1997

Nonlinear effects above 2 µm in chalcogenide suspended core microstructured optical fibers: Modeling and experiments

2011

We present our latest results on the linear and nonlinear modeling, and on the fabrication of chalcogenide suspended core microstructured optical fibers for mid-infrared generation. We focus on an AsSe glass composition. We have used a thulium-doped fiber laser to pump our fibers around 2 µm. In order to enhance further the nonlinearities and to manage the chromatic dispersion for supercontinuum application, we have tapered some of our microstructured optical fibers.

Asymmetrically Apodized Fiber Bragg Gratings for Applications in Dispersion-Less Fabry-Pérot Fiber Cavities

2010

Abstract This article presents a theoretical study of the dispersion properties of the asymmetrically apodized fiber Bragg gratings. It is shown that the dispersive behavior of these gratings may be changed from normal to anomalous, depending on the apodization function and the grating strength. The asymmetrical Bessel functions were chosen in order to demonstrate these properties of the gratings. The application of this effect in a dispersion-less Fabry-Perot fiber cavity formed by two asymmetrically apodized fiber Bragg gratings is discussed.

Linearly polarized all-fiber laser using a short section of highly polarizing microstructured fiber

2007

A linearly polarized all-fiber erbium laser is presented in this work. The polarization selective element consists on a piece of a single-mode, polarizing microstructured fiber, which is placed within the laser cavity. The microstructured fiber shows a regular lattice of air-holes, in which four holes next to the core were enlarged. This fiber shows a polarization dependent loss of 16 dB/m around 1550 nm. The laser cavity presents different losses for each polarization and, as a consequence, a highly polarized emission is obtained. The polarization ratio of the emitted power was in excess of 20 dB.

Tunable dispersion device based on a tapered fiber Bragg grating and nonuniform magnetic fields

2003

We present a new variable dispersion device based on tuning the chirp of a tapered fiber Bragg grating by means of a magnetic transducer. By using a nonuniform magnetic field, we demonstrate a 188-472-ps/nm dispersion tuning range, suitable for tunable radio-frequency filters and dispersion compensation, among others.

Chromatic Dispersion Control in Mode-Locked Yb-Doped Fiber Lasers Based on a Microstructured Optical Fiber

2013

We present an experimental study on the use of solid core microstructured optical fibers (MOF) for managing the chromatic dispersion in an Yb-doped fiber laser passively mode-locked by a saturable absorber. The performance of the laser, in terms of pulse width and repetition rate, was investigated as a function of the net cavity dispersion.

Sorption of copper by a highly mineralized peat in batch and packed-bed systems

2009

BACKGROUND: The performance of peat for copper sorption was investigated in batch and fixed-bed experiments. The effect of pH was evaluated in batch experiments and the experimental data were fitted to an equilibrium model including pH dependence. Hydrodynamic axial dispersion was estimated by tracing experiments using LiCl as a tracer. Six fixed-bed experiments were carried out at copper concentrations between 1 and 60 mg dm−3 and the adsorption isotherm in dynamic mode was obtained. A mass transport model including convection–dispersion and sorption processes was applied for breakthrough curve modelling. RESULTS: Maximum uptake capacities in batch mode were 22.0, 36.4, and 43.7 mg g−1 for…

Agglomeration and dispersion of economic activities in and around Paris: An exploratory spatial data analysis

2010

The agglomeration patterns of twenty-six manufacturing and service sectors in and around Paris in 1999 are analysed. The method used measures the intensity of spatial agglomeration and identifies the location patterns of economic sectors. First the locational Gini coefficient and Moran’s I statistics of global spatial autocorrelation are computed. These provide different but complementary information about the spatial agglomeration of the sectors under study. Then exploratory spatial data analysis tools are applied. Moran scatterplots and local indicators of spatial association statistics reveal great diversity in location patterns across sectors.

Dispersive evaluation of the D-term form factor in deeply virtual Compton scattering

2014

We present a dispersive representation of the D-term form factor for hard exclusive reactions, using unsubtracted $t$-channel dispersion relations. The $t$-channel unitarity relation is saturated with the contribution of two-pion intermediate states, using the two-pion distributions amplitude for the $\gamma^*\gamma\rightarrow \pi\pi$ subprocess and reconstructing the $\pi\pi\rightarrow N\bar N$ subprocess from available information on pion-nucleon partial-wave helicity amplitudes. Results for the D-term form factor as function of $t$ as well as at $t=0$ are discussed in comparison with available model predictions and phenomenological parametrizations.

Structure of pion photoproduction amplitudes

2018

We derive and apply the finite energy sum rules to pion photoproduction. We evaluate the low energy part of the sum rules using several state-of-the-art models. We show how the differences in the low energy side of the sum rules might originate from different quantum number assignments of baryon resonances. We interpret the observed features in the low energy side of the sum rules with the expectation from Regge theory. Finally, we present a model, in terms of a Regge-pole expansion, that matches the sum rules and the high-energy observables.