97 research outputs found
Er doped oxide nanoparticles in silica based optical fibres
Erbium doped materials are of great interest in optical telecommunications
due to the Er3+ intra-4f emission at 1.54 ?m. Erbium doped fibre amplifiers
(EDFA) were developed in silica glass because of the low losses at this
wavelength and the reliability of this glass. Developments of new rare earth
doped fibre amplifiers aim to control their spectroscopic properties including
shape and width of the gain curve and optical quantum efficiency. Standard
silica glass modifiers, such as aluminium, result in very good properties in
current EDFA. However, for more drastic spectroscopic changes, more important
modifications of the rare earth ions local environment are required. To address
this aim, we present a fibre fabrication route creating rare earth doped
calcia?silica or calcia?phosphosilica nanoparticles embedded in silica glass.
By adding alkaline earth elements such as calcium, in low concentration, one
can obtain a glass with an immisci- bility gap so that phase separation occurs
with an appropriate heat treatment. We investigated the role of two elements:
calcium and phosphorus (a standard silica modifier). Scanning electron
microscopy shows that nanoparticles are only observed when calcium is
incorporated. The size of the particles is determined to be around 50 nm in
preform samples. The nature of these particles depends on phosphorus content:
without P, electron diffraction shows that the particles are amorphous whilst
they are partially crystalline when phosphorus is added. In addition through
use of energy dispersive x-ray techniques, we have shown that erbium ions are
located in the nanoparticles
Action de l’adrénaline et de quelques sympathomimétiques sur la motricité digestive des Equidés
Brunaud M., Dussardier Michel. Action de l’adrénaline et de quelques sympathomimétiques sur la motricité digestive des Equidés. In: Bulletin de l'Académie Vétérinaire de France tome 108 n°5, 1955. pp. 175-181
Birefringence analysis of multilayer leaky cladding optical fibre
We analyse a multilayer leaky cladding (MLC) fibre using the finite element
method and study the effect of the MLC on the bending loss and birefringence of
two types of structures: (i) a circular core large-mode-area structure and (ii)
an elliptical-small-core structure. In a large-mode-area structure, we verify
that the multilayer leaky cladding strongly discriminates against higher order
modes to achieve single-mode operation, the fibre shows negligible
birefringence, and the bending loss of the fibre is low for bending radii
larger than 10 cm. In the elliptical-small-core structure we show that the MLC
reduces the birefringence of the fibre. This prevents the structure from
becoming birefringent in case of any departures from circular geometry. The
study should be useful in the designs of MLC fibres for various applications
including high power amplifiers, gain flattening of fibre amplifiers and
dispersion compensation.Comment: 18 page
Characterization of Erbium-Doped Nanoparticles in Transparent Glass Ceramic Optical Fibres
We report on using nanometric mass spectroscopy and molecular dynamics modelling to characterize the composition and structure of self-grown erbium-doped nanoparticles in transparent glass ceramic optical fibres fabricated by modified chemical vapour deposition without post-ceramming
Co-axial dual-core resonant leaky fibre for optical amplifiers
We present a co-axial dual-core resonant leaky optical fibre design, in which
the outer core is made highly leaky. A suitable choice of parameters can enable
us to resonantly couple power from the inner core to the outer core. In a
large-core fibre, such a resonant coupling can considerably increase the
differential leakage loss between the fundamental and the higher order modes
and can result in effective single-mode operation. In a small-core single-mode
fibre, such a coupling can lead to sharp increase in the wavelength dependent
leakage loss near the resonant wavelength and can be utilized for the
suppression of amplified spontaneous emission and thereby gain equalization of
an optical amplifier. We study the propagation characteristics of the fibre
using the transfer matrix method and present an example of each, the
large-mode-area design for high power amplifiers and the wavelength tunable
leakage loss design for inherent gain equalization of optical amplifiers.Comment: 6 page
Presentation and Preliminary Results of DROĂŹD Project: Development of a Distributed Optical Fibre Dosimeter
International audienceABSTRACT DROĂŹD project is intended to develop a distributed optical fibre dosimeter based on Radiation-Induced Attenua-tion (RIA). The RIA will be measured by a high resolution Optical Time Domain Reflectometry (OTDR) technique that allows to locate the irradiated fibre section. The first part of the project focuses on designing a high radiation sensitive fibre. As a preliminary work, the attenu-ation of several fibres with various compositions has been recorded in situ during and after irradiation. The experimental setup and RIA values are presented and discussed. Several dopants and their combinations have been identified as a good starting point to design a highly radiation sensitive fibre
Enhanced Raman Scattering of amorphous matrices for Fiber Optics Sensor
International audienc
Spectroscopic characteristics of Er-doped LiNbO<sub>3</sub>
Er-doped LiNbO3 has recently been strongly pursued as an integrated laser source at 1550nm due to the potential offered by the host material for electro-optic, acousto-optic and non-linear interactions, and several devices have been demonstrated for advanced laser applications. To fully exploit this laser system, it is important to know the spectral characteristics of the dopant-host combination and to quantify the radiative and nonradiative transitions between different excited levels in order to be able to predict and optimise the device performance. For example, it is well known that pumping Er-doped devices at 980nm provides high efficiencies (in dB/mW) and signal-to-noise ratios. However, the Er:LiNbO3 devices demonstrated thus far have been pumped at 1480nm, due to the problems associated with photorefractive damage and upconversion at 980nm. Recent results in Nd:LiNbO3 have shown that the photorefractive damage at near IR wavelengths can be suppressed sufficiently to allow laser operation. Furthermore, recent investigations using XSW have revealed that Er3+ ions in LiNbO3 are located in an octahedral position close to a Li site, thus allowing the incorporation of high concentrations of Er3+ in this host material without fluorescence quenching. This leads to the belief that the upconversion at 980nm is due to a resonant two stage ESA process involving a single erbium ion. In this paper we present a Judd-Ofelt analysis of Er3+ ions in LiNbO3 using measured line-strengths of 10 transitions from the ground state to excited state manifolds, and use these line strengths to evaluate ESA transition strengths from the 4 I 13/2 and 4 I 9/2 levels. Measured oscillator strengths at 300K are compared with calculated electric and magnetic dipole oscillator strengths and the results are found to be within the typical uncertainties associated with these types of calculations. Measured and calculated lifetimes will be compared and used to deduce the quantum efficiencies of the various excited levels. Upconversion at 980nm will be discussed in the light of these results
Erbium-doped transparent glass ceramic optical fibres: Characterization using mass spectroscopy and molecular dynamics modeling
Rare earth (RE) doped silica-based optical fibres with transparent glass ceramic (TGC) core were fabricated through the well-known modified chemical vapor deposition (MCVD) process without going through the commonly used stage of post-ceramming. The main characteristics of the RE-doped
dielectric nanoparticles (DNP), their density and mean diameter in thefibres are dictated by various parameters. This paper reports on progresses in the fine characterization of the nanopaticles, particularly their dimensions and composition, using nanosclae mass spectroscpy and molecular dynamics modeling, and alteration of the spectroscopic properties of the erbium ions embedded within the phospho-silicate DNP. These results permit to get more insight into the complex process of the
DNP self-nucleation and growth during the fibre fabrication process. This fabrication route could have important potentials in improving rare-earth-doped fibre amplifiers and laser sources
Design and fabrication of an intrinsically gain flattened Erbium doped fiber amplifier
We report design and subsequent fabrication of an intrinsically gain
flattened Erbium doped fiber amplifier (EDFA) based on a highly asymmetrical
and concentric dual-core fiber, inner core of which was only partially doped.
Phase-resonant optical coupling between the two cores was so tailored through
optimization of its refractive index profile parameters that the longer
wavelengths within the C-band experience relatively higher amplification
compared to the shorter wavelengths thereby reducing the difference in the
well-known tilt in the gains between the shorter and longer wavelength regions.
The fabricated EDFA exhibited a median gain ?28 dB (gain excursion below
2.2 dB within the C-band) when 16 simultaneous standard signal channels
were launched by keeping the I/P level for each at ?20 dBm/ channel. Such EDFAs
should be attractive for deployment in metro networks, where economics is a
premium, because it would cut down the cost on gain flattening filter head
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