Amplification de 8 modes (groupes de modes LP11 et LP21) avec gain différentiel ajustable

National audienceRÉSUMÉ: Nous proposons une analyse numérique d'une fibre amplifiant les groupes de modes LP11 et LP21 d'une fibre faiblement multimode avec un gain modal différentiel ajustable. La fibre se compose d'un cœur central et d'un cœur annulaire qui est dopé aux ions Er3+. Les modes du cœur central de la fibre amplificatrice sont excités par les modes de la fibre de transport faiblement multimode et sont convertis dans des modes appropriés du cœur annulaire de la fibre amplificatrice. Le couplage entre les modes du cœur central et les modes du cœur périphérique annulaire se fait par l’intermédiaire de réseaux asymétriques à pas long. L'amplification pour les deux groupes de modes se fait sur des longueurs indépendantes ce qui permet d'ajuster le gain différentiel. Les modes annulaires amplifiés sont recouplés dans les modes de cœurs par des réseaux asymétriques à pas longs appairés aux premiers réseaux

Large mode area leaky optical fiber fabricated by MCVD

Manuscript : 17 pages, 3 figuresInternational audienceA large mode area single-mode optical fiber based on leaky mode filtering has been prepared by modified chemical vapor deposition (MCVD) technique. The fiber has a leaky cladding, which discriminates the fundamental mode from the higher order ones. A preliminary version has 25-µm core diameter and 0.11 numerical aperture. A Gaussian-like mode with 22-µm mode field diameter has been observed after 3-m propagation, in agreement with modeling

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

Phylogenetic diversity analysis of Trichoderma species based on internal transcribed spacer (ITS) marker

The phylogeny of Trichoderma and the phylogenetic relationships of its species was investigated by maximum parsimony analysis and distance analysis of DNA sequences from multiple genetic loci 18S rDNA sequence analysis suggests that the genus Trichoderma evolved at the same time as Hypomyces and Fusarium and thus about 110 Myr ago 28S rDNA sequence analysis shows that the genus Trichoderma is part of a monophyletic branch within the Hypocreaceae. Most isolates of the genus Trichoderma were found to act as mycoparasites of many economically important aerial and soil-borne plant pathogens. Trichoderma has attained importance as a substitute for chemical pesticides and hence an attempt was intended to corroborate the positive relatedness of molecular and morphological characters. Two fungal strains, Trichoderma koningii Tk-5201/CSAU and Trichoderma virens Tvi-4177/CSAU were isolated from a soil sample collected from CSA Farm, Kanpur district of Uttar Pradesh, India. The universal primers (internal transcribed spacer, ITS) were used for the amplification of 18S rRNA gene fragment and strains were thus characterized with the help of ITS marker. It is proposed that the identified strains T. koningii Tk-5201/CSAU and T. virens Tvi-4177/CSAU be assigned as the type strains of a species of genus Trichoderma based on phylogenetic tree analysis together with the 18S rRNA gene sequence search in Ribosomal Database Project, small subunit rRNA and large subunit rRNA databases. The sequence was deposited in GenBank with the accession numbers KC800923 and KC800924, respectively. Thus an integrated approach of morphological and molecular markers can be employed to identify a superior strain of Trichoderma for its commercial exploitation.Keywords: 18S ribosomal RNA gene, Trichoderma, phylogenetic analysis, internal transcribed spacer (ITS), DNA sequencing, GenBankAfrican Journal of Biotechnology, Vol. 13(3), pp. 449-455, 15 January, 201

Autonomous Underwater Robot

Mathematical modeling, simulation and manage of an underwater robot are a totally complicated assignment because of its nonlinear dynamic structure. in this paper, the authors present kinematic and dynamic modeling of an underwater robot with rotating thrusters. Through a digital environment implemented in MATLAB and LabVIEW, the performance of the proposed robotic underneath real running conditions turned into validated

HingeInflex: a MATLAB-based method for precise selection of the hinge and the inflection points in folds

Subjectivity in visual selection of hinge and inflection points leads to significant errors in analyses of fold shapes in profile sections. This article gives a method for precise determination of these points. The method: (1) imports a fold image into MATLAB, (2) digitizes points on the image, (3) increases the number of available points by using an interpolation algorithm, (4) fits a polynomial curve to the points, and (5) searches for the hinge and the inflection points mathematically. Tests on several folds confirm that the 'HingeInflex' is a rapid, robust and user-friendly method for precise selection of the hinge and inflection points