135 research outputs found
Influence of specific codopants and post-treatments on Erbium Doped Fibers: Radiation behavior characteristics by CML
No full textInfluence of Ce codoping and H2 pre-loading on Er/Yb-doped fiber: Radiation response characterized by Confocal Micro-Luminescence
No full textConfocal microscopy luminescence measurements were applied to study the X-ray radiation response of
Er/Yb-doped optical fibers in connection with H2 pre-loading and with the addition of another lanthanide
element (Cerium) in the core composition. Laser excitations at 488 nm and 325 nm allow deriving the
emission and absorption pattern of Er3+, the latter derived from the dips appearing in a wide luminescence
band related to defects in silica. We found that the luminescence spectrum of the X-irradiated Er/Yb-doped
core fiber evidences an increase in the emission intensity around 520 and 660 nm; in contrast, no changes are
induced by radiation neither after H2 pre-loading nor when the Cerium is added to the core composition. Both
treatments reduce the generation of defects in the Er-doped fibers thus providing hardness in the radiative
environment
Coupled experiment/simulation approach for the design of radiation-hardened rare-earth doped optical fibers and amplifiers
No full textWe developed an approach to design radiation-hardened rare earth -doped fibers and amplifiers. This methodology combines testing experiments on these devices with particle swarm optimization (PSO) calculations. The composition of Er/Yb-doped phosphosilicate fibers was improved by introducing Cerium inside their cores. Such composition strongly reduces the amplifier radiation sensitivity, limiting its degradation: we observed a gain decreasing from 19 dB to 18 dB after 50 krad whereas previous studies reported higher degradations up to 0°dB at such doses. PSO calculations, taking only into account the radiation effects on the absorption efficiency around the pump and emission wavelengths, correctly reproduce the general trends of experimental results. This calculation tool has been used to study the influence of the amplifier design on its radiation response. The fiber length used to ensure the optimal amplification before irradiation may be rather defined and adjusted to optimize the amplifier performance over the whole space mission profile rather than before integration in the harsh environments. Both forward and backward pumping schemes lead to the same kind of degradation with our active fibers. By using this promising coupled approach, radiation-hardened amplifiers nearly insensitive to radiations may be designed in the future
Radiation hardening of Rare-Earth doped fiber amplifiers
No full textWe investigated the radiation hardening of optical fiber amplifiers operating in space environments. Through a
real-time analysis in active configuration, we evaluated the role
of Ce in the improvement of the amplifier performance against
ionizing radiations. Ce-codoping is an efficient hardening solution, acting both in the limitation of defects in the host glass matrix of RE-doped optical fibers and in the stabilization of lasing properties of the Er3+-ions. On the one hand, in the nearinfrared
region, radiation induced attenuation measurements show the absence of radiation induced P-related defect species in host glass matrix of the Ce-codoped active fibers; on the other
hand, in the Ce-free fiber, the higher lifetime variation shows stronger local modifications around the Er3+-ions with the absence of Ce
Combined experimental and simulation study of the fiber composition effects on its Brillouin scattering signature
No full textBrillouin signatures of 15 fibers are characterized experimentally and theoretically highlighting the core and cladding dopants influence. Tailoring the fiber composition and refractive index profile, multi-peak fibers allowing discriminating between temperature and strain appear feasible
Unité chrétienne et tolérance religieuse, par le Pasteur J. Cadier, Mgr Chevrot, Abbé P. Couturier, Pasteur J. Delpech, R. Fédou, J. Guitton, A. Latreille, G. Marcel, Mgr Metzger, R. P. Pribilla, Pasteur M. Thurian, (Collection Dialogues) 1950 ; Tolérance et Communauté humaine. Chrétiens dans un monde divisé par R. Aubert, L. Bouyer, L. Cerfaux, Y. Congar, A. Dondeyre, A. Léonard, J. Masson, A. Molitor, B. Olivier, H. D. Robert, 1952
No full textNédoncelle Maurice. Unité chrétienne et tolérance religieuse, par le Pasteur J. Cadier, Mgr Chevrot, Abbé P. Couturier, Pasteur J. Delpech, R. Fédou, J. Guitton, A. Latreille, G. Marcel, Mgr Metzger, R. P. Pribilla, Pasteur M. Thurian, (Collection Dialogues) 1950 ; Tolérance et Communauté humaine. Chrétiens dans un monde divisé par R. Aubert, L. Bouyer, L. Cerfaux, Y. Congar, A. Dondeyre, A. Léonard, J. Masson, A. Molitor, B. Olivier, H. D. Robert, 1952. In: Revue des Sciences Religieuses, tome 27, fascicule 3, 1953. pp. 313-314
Unité chrétienne et tolérance religieuse, par le Pasteur J. Cadier, Mgr Chevrot, Abbé P. Couturier, Pasteur J. Delpech, R. Fédou, J. Guitton, A. Latreille, G. Marcel, Mgr Metzger, R. P. Pribilla, Pasteur M. Thurian, (Collection Dialogues) 1950 ; Tolérance et Communauté humaine. Chrétiens dans un monde divisé par R. Aubert, L. Bouyer, L. Cerfaux, Y. Congar, A. Dondeyre, A. Léonard, J. Masson, A. Molitor, B. Olivier, H. D. Robert, 1952
No full textNédoncelle Maurice. Unité chrétienne et tolérance religieuse, par le Pasteur J. Cadier, Mgr Chevrot, Abbé P. Couturier, Pasteur J. Delpech, R. Fédou, J. Guitton, A. Latreille, G. Marcel, Mgr Metzger, R. P. Pribilla, Pasteur M. Thurian, (Collection Dialogues) 1950 ; Tolérance et Communauté humaine. Chrétiens dans un monde divisé par R. Aubert, L. Bouyer, L. Cerfaux, Y. Congar, A. Dondeyre, A. Léonard, J. Masson, A. Molitor, B. Olivier, H. D. Robert, 1952. In: Revue des Sciences Religieuses, tome 27, fascicule 3, 1953. pp. 313-314
Radiation hardening of optical fibers and fiber sensors for space applications: recent advances
No full textIn these ICSO proceedings, we review recent advances from our group concerning the radiation hardening of
optical fiber and fiber-based sensors for space applications and compare their benefits to state-of-the-art results.
We focus on the various approaches we developed to enhance the radiation tolerance of two classes of optical
fibers doped with rare-earths: the erbium (Er)-doped ones and the ytterbium/erbium (Er/Yb)-doped ones. As a
first approach, we work at the component level, optimizing the fiber structure and composition to reduce their
intrinsically high radiation sensitivities. For the Erbium-doped fibers, this has been achieved using a new
structure for the fiber that is called Hole-Assisted Carbon Coated (HACC) optical fibers whereas for the Er/Ybdoped
optical fibers, their hardening was successfully achieved adding to the fiber, the Cerium element, that
prevents the formation of the radiation-induced point defects responsible for the radiation induced attenuation in
the infrared part of the spectrum. These fibers are used as part of more complex systems like amplifiers
(Erbium-doped Fiber Amplifier, EDFA or Yb-EDFA) or source (Erbium-doped Fiber Source, EDFS or YbEDFS),
we discuss the impact of using radiation-hardened fibers on the system radiation vulnerability and
demonstrate the resistance of these systems to radiation constraints associated with today and future space
missions. Finally, we will discuss another radiation hardening approach build in our group and based on a
hardening-by-system strategy in which the amplifier is optimized during its elaboration for its future mission
considering the radiation effects and not in-lab
Adaptation of a digital marketing strategy to attract North American customers
No full textDigital marketing has become an integral part of the language schools strategies. Consequently, the massive use of digital channels has created a need to differentiate from the online competition and target leads geographically. The current digital strategy developed by LSF Montpellier has shown a positive impact on sales performance and managers have integrated the challenge to improve the current strategy to increase traffic on the website and generate more conversions. Beyond these objectives, the purpose of this research work is to propose a development plan of the current digital strategy to attract customers located in the United States.
The scope of the following thesis is a specific situation. The commissioning company is a French language school located in Montpellier with a high sales performance and a high customer satisfaction rate.
The theoretical data applies to digital strategy, inbound marketing and language school business. The theoretical part is based on an analytical work of the various authors who have written articles, books and e-books related to the selected thesis topic. The author has also realized a data selection through blogs and content curation platforms. The field work part is the result of a cross-sectional qualitative study administered to the strategic and digital expertise of the case company.
The analysis of the questionnaire has shown many areas of improvement related to the digital strategy. The study showed that website content is not sufficient for attracting and converting leads.
The adaptation plan proposed by the author includes a greater adoption of inbound marketing combined to a clearly defined lead nurturing strategy. Moreover, the author recommends using geo-targeted digital marketing methods including remarketing, pay-per-click advertising and website content delivering
Temporal evolution and correlation between cooperative luminescence and photodarkening in ytterbium doped silica fibers
No full textThe present work describes photodarkening from the viewpoint of cooperative luminescence. The temporal evolution of both effects was measured simultaneously by means of ytterbium doped aluminosilicate fibers for concentrations up to 1.8 wt% Yb3+. The quadratic dependence of photodarkening and cooperative luminescence versus dopant concentration was observed. The change in the photodarkening and cooperative luminescence mutual dynamics for highly and low doped fibers is ascribed to a different ion number which forms the cluster. Cooperative luminescence is proved to be a natural probe for photodarkening since it provides new pieces of information and contributes to the photodarkening mechanism descriptio
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