Hybrid silicon-fiber funable multi-wavelength laser with switchable frequency spacing

Agile optical systems and elastic optical networks demand for flexible, high-performance laser sources. We demonstrate a hybrid silicon-fiber laser that can be largely tuned in wavelength, switched in frequency spacing and easily switched between multi- and single-wavelength operations. Single-mode laser with a fiber-coupled output power of 6 to 8 dBm was measured across the spectral range of 1545 nm to 1560 nm. No significant sign of power limitation from nonlinear absorption or free carrier generation in silicon was found. It is thus expected that a higher output can be obtained by improving the gain saturation performances as well as the fiber-to-chip coupling efficiency. For multi-wavelength operation, we have achieved a frequency spacing switchable between 56 GHz, 75 GHz, and 225 GHz. For both the multi- and single-wavelength operations, a linewidth of less than 20 kHz was measured. All the tuning mechanisms have been realized on the silicon chip, providing a scalable solution for tunable fiber lasers with minimized cost and integration complexity

Une méthode d'estimation de la consommation de puissance pour un système sur puce

RÉSUMÉ Estimer la consommation de puissance le plus tôt possible durant le cycle de développement est important pour pouvoir rencontrer le temps de mise en marché. Pour cela, plusieurs recherches en consommation de puissance se tournent vers l'estimation à haut niveau, comme la Modélisation au Niveau Transactionnel (TLM), pour accélérer l’obtention des estimations de puissance. Ce travail présente une méthodologie à haut-niveau orienté sur les Coeur sous licence (IP) qui effectue une estimation de puissance. La méthode propose une distinction entre l'activité de l'IP concerné et de son implémentation. Ceci permet de facilement créer un modèle qui peut être réutilisé avec différentes fréquences et implémentations. En utilisant l'information obtenue par des mesures d'une description au Niveau Registre (RTL), un modèle peut-être créé pour des simulations haut-niveau permettant d'abstraire l'implémentation. La méthodologie est présentée sur un processeur, une mémoire, un bus, une minuterie et un Contrôleur d'Interruption de Processeur (PIC) de Xilinx. En comparaison à des estimations effectuées au niveau RTL, le modèle permet d'estimer la consommation de puissance avec une précision de 25 ±10% par rapport à une estimation effectuée avec Xpower; et ce avec un facteur accélération de trois ou quatre ordres de grandeur.---------- ABSTRACT Estimating the power consumption of System on Chip as early as possible in the design life cycle is important to meet the time to market requirements. For this purpose, most research is turning toward high-level models, like the Transaction-Level Modeling (TLM), to estimate power earlier. This work presents a high-level Intellectual Property core (IP) oriented power estimation methodology. The methodology separates the activity of the IP from the implementation. This allows the ability to easily create a model that can be used with different frequencies, layout and implementation technology. By using data gathered from the Register-Transfer Level (RTL) a model can be created for high-level simulation that can take into account the technology and characteristics of the Field-Programmable Gate Array (FPGA) device. The methodology is presented in this work for a processor, its local memory IP, counter, Processor Interrupt Controller (PIC) and bus from Xilinx. Compared to estimations made at the RTL level, the resulting model gives accurate results of 25% ±10% compared to a Xpower estimate with three to four order speedups and through different implementations

Source laser accordable jumelant photonique sur silicium et fibre optique

Ce mémoire porte sur la conception de lasers hybrides jumelant les bres optiques à la photonique sur silicium. L'objectif principal est de réaliser un laser polyvalent au niveau de ses paramètres d'émission et permettant en plus d'offrir des performances intéressantes pour les communications optiques. Plusieurs approches menant à l'intégration laser sur la plateforme de photonique sur silicium ont été démontrées. Contrairement aux approches d'intégration qui visent à produire une source la plus compacte qui soit, l'approche choisie vise à réaliser un laser performant qui exploite à la fois les performances d'amplication optique des bres dopées ainsi que le potentiel de traitement optique qu'offre la plateforme de photonique sur silicium. Le principe de fonctionnement de même que les modèles théoriques de différentes structures optiques accessibles grâce à la plateforme de photonique sur silicium sont présentés en détail. Ces structures, permettant le guidage optique à l'échelle nanoscopique de même que la manipulation de la lumière, sont des éléments clés pour la conception de ltres optiques pour les cavités laser. Les performances d'un ltre Vernier sur silicium sont analysées grâce à des simulations numériques. Deux types de lasers hybrides accordables sont présentés dans ce document : celui d'un laser multimodes opérant à 1.55 µm et permettant une sélection de l'espacement spectral entre ses modes et celui d'un laser monomode opérant à 2 µm et accordable sur une large plage spectrale. Dans le premier cas, le milieu d'amplication de la cavité est composé d'une bre optique dopée à l'erbium tandis que dans le second, il s'agit d'une bre dopée au thulium. Les différents éléments de la cavité sont modélisés et leurs performances sont simulées à l'aide d'outils numériques. Enn, les performances expérimentales des lasers sont mesurées en laboratoire.This master's thesis is on the design of a hybrid laser combining optical bers and the technology of silicon photonics. The main objective is to achieve a laser with great control and exibility over its emission parameters and with good performances for the eld of optical telecommunications. Until now, several approaches leading to laser integration on the silicon photonics have been demonstrated. Unlike integration approaches which aim to produce the most compact source possible, the chosen approach aims to produce a high-performance laser which exploits both the optical amplication performance of the doped bers as well as the potential of light processing and precision that oers the silicon photonic platform. The operating principle as well as the theoretical models of dierent optical devices accessible thanks to the silicon photonics are presented in detail. These devices allowing optical connement at the 100-nanometer scale level as well as the manipulation of light are key elements in the design of optical lters for the laser cavity. The performances of a Vernier lter on silicon are analyzed by means of numerical simulations. Two types of hybrid lasers are presented in this document. The rst is a multimode laser allowing a selection of the spectral spacing between its modes. The second type of laser is a single-mode laser operating at 2000 nm and tunable over a range of 100 nm. In the rst case, the amplication medium of the cavity is composed of an optical ber doped with erbium while in the second, it is a ber doped with thulium

The Spiral Structure of the Milky Way, Cosmic Rays, and Ice Age Epochs on Earth

The short term variability of the Galactic cosmic ray flux (CRF) reaching Earth has been previously associated with variations in the global low altitude cloud cover. This CRF variability arises from changes in the solar wind strength. However, cosmic ray variability also arises intrinsically from variable activity of and motion through the Milky Way. Thus, if indeed the CRF climate connection is real, the increased CRF witnessed while crossing the spiral arms could be responsible for a larger global cloud cover and a reduced temperature, thereby facilitating the occurrences of ice ages. This picture has been recently shown to be supported by various data (Shaviv, 2001). In particular, the variable CRF recorded in Iron meteorites appears to vary synchronously with the appearance ice ages. Here we expand upon the original treatment with a more thorough analysis and more supporting evidence. In particular, we discuss the cosmic ray diffusion model which considers the motion of the Galactic spiral arms. We also elaborate on the structure and dynamics of the Milky Way's spiral arms. In particular, we bring forth new argumentation using HI observations which imply that the galactic spiral arm pattern speed appears to be that which fits the glaciation period and the cosmic-ray flux record extracted from Iron meteorites. In addition, we show that apparent peaks in the star formation rate history, as deduced by several authors, coincides with particularly icy epochs, while the long period of 1 to 2 Gyr before present, during which no glaciations are known to have occurred, coincides with a significant paucity in the past star formation rate.Comment: 33 pages, 11 figures. To Appear in New Astronom

Understanding the role of contrasting urban contexts in healthy aging: an international cohort study using wearable sensor devices (the CURHA study protocol).

BACKGROUND: Given the challenges of aging populations, calls have been issued for more sustainable urban re-development and implementation of local solutions to address global environmental and healthy aging issues. However, few studies have considered older adults' daily mobility to better understand how local built and social environments may contribute to healthy aging. Meanwhile, wearable sensors and interactive map-based applications offer novel means for gathering information on people's mobility, levels of physical activity, or social network structure. Combining such data with classical questionnaires on well-being, physical activity, perceived environments and qualitative assessment of experience of places opens new opportunities to assess the complex interplay between individuals and environments. In line with current gaps and novel analytical capabilities, this research proposes an international research agenda to collect and analyse detailed data on daily mobility, social networks and health outcomes among older adults using interactive web-based questionnaires and wearable sensors. METHODS/DESIGN: Our study resorts to a battery of innovative data collection methods including use of a novel multisensor device for collection of location and physical activity, interactive map-based questionnaires on regular destinations and social networks, and qualitative assessment of experience of places. This rich data will allow advanced quantitative and qualitative analyses in the aim to disentangle the complex people-environment interactions linking urban local contexts to healthy aging, with a focus on active living, social networks and participation, and well-being. DISCUSSION: This project will generate evidence about what characteristics of urban environments relate to active mobility, social participation, and well-being, three important dimensions of healthy aging. It also sets the basis for an international research agenda on built environment and healthy aging based on a shared and comprehensive data collection protocol

Retrospective Study Looking at Cinacalcet in the Management of Hyperparathyroidism after Kidney Transplantation

Objectives. The primary objective of this study is to evaluate the use of cinacalcet in the management of hyperparathyroidism in kidney transplant recipients. The secondary objective is to identify baseline factors that predict cinacalcet use after transplantation. Methods. In this single-center retrospective study, we conducted a chart review of all patients having been transplanted from 2003 to 2012 and having received cinacalcet up to kidney transplantation and/or thereafter. Results. Twenty-seven patients were included with a mean follow-up of 2.9±2.4 years. Twenty-one were already taking cinacalcet at the time of transplantation. Cinacalcet was stopped within the first month in 12 of these patients of which 7 had to restart therapy. The main reason for restarting cinacalcet was hypercalcemia. Length of treatment was 23±26 months. There were only 3 cases of mild hypocalcemia. There was no statistically significant association between baseline factors and cinacalcet status a year later. Conclusions. Discontinuing cinacalcet within the first month of kidney transplantation often leads to hypercalcemia. Cinacalcet appears to be an effective treatment of hypercalcemic hyperparathyroidism in kidney transplant recipients. Further studies are needed to evaluate safety and long-term benefits