Etude système de diodes lasers à verrouillage de modes pour la radio-sur-fibre en bande millimétrique

Ce travail de thèse s inscrit dans la recherche des solutions économiquementviables pour des réseaux personnels à hauts débits (plusieurs Gbps à plusieursdizaines de Gbps) opérationnels en bande millimétrique autour de 60 GHz. Aucas où ces réseaux servent un nombre élevé d utilisateurs, ils comprendront unemultitude d antennes afin d assurer l accès sans fil rapide. Afin de réduire aumaximum le coût d un module d antenne, les réseaux doivent fournir un signalanalogue à des porteuses millimetriques. Une solution prometteuse pour les systèmesde distribution qui correspond à ces besoins sont des structures à fibreoptique, laquelle permet une transmission à faibles pertes et à haute bande passante.On parle de l approche "radio-sur-fibre" (en anglais, radio-over-fiber). Laproblématique est de pouvoir générer et moduler un signal aux fréquences millimétriqueslors de la transmission optique - et ce avec des composant bas coûts.La technique utilisée dans le cadre de cette thèse est l emploi des diodes laser àverrouillage de modes. Ces derniers vont pouvoir générer des hautes fréquencestout en ne nécessitant qu une alimentation continue, et ils peuvent être modulésde manière directe ou externe. Les lasers à semi-conducteurs employés ici sontd une génération encore à l état d étude puisqu il s agit des lasers à boites (ouîlots) quantiques. Ces lasers ont montrés de très bonnes capacités à générer dessignaux électriques aux fréquences autour de 60 GHz, bien qu ayant encore, pourl instant, à une stabilité de fréquence (ou de phase) limitée. Dans le cadre des systèmesde communication opto/micro-ondes, peu de travaux approfondis ont étémenés sur ces structures.Au cours de cette thèse, plusieurs études ont été effectuées. La première portesur les propriétés générales d un système construit à partir de ce type de laser(puissances disponibles, figure de bruit, linéarité etc.). Une deuxième étude aété consacrée aux effets de la propagation des signaux dans les systèmes baséssur les lasers à verrouillage de modes, notamment de la dispersion chromatiquelaquelle a un effet considérable sur les distances de transmission. Les deux étudesmettent en avant l importance d une limitation du nombre de modes générés parla diode laser afin d optimiser non seulement le gain du lien et la puissance RFrécupérée, mais aussi la figure de bruit du système. Lors d une troisième étude, lastabilité en fréquence/phase s est révélée critique, car le bruit de fréquence/phaselimite la qualité de la transmission en introduisant un plancher d erreur mêmepour des rapports signal-a-bruit très élevés. Des différentes générations de lasersà boites (îlots) quantiques et à verrouillage de modes ont été testées. Le problèmedu bruit de fréquence et de phase persiste et ne peut pas être résolu en utilisantles techniques classiques comme les boucles à verrouillage de phase conventionnelles.Une solution pour ce problème a été développée pour les systèmes detransmission; elle permet simultanément un ajustement de fréquence supérieure(précision de quelques Hz à quelques kHz) à celle donnée par le processus de fabricationdes diodes lasers (précision de quelques GHz), ainsi qu une stabilisationde fréquence et de phase.This dissertation is related to the search for an economically sustainable solutionfor high data rate (several Gbps to several tens of Gbps) personal area networksoperating in the millimeter-wave region around 60 GHz. If such networks supplya large number of users, they need to encompass a multitude of antenna pointsin order to assure wireless access to the network. With the aim of reducing thecost of an antenna module, the networks should at best provide quasi "readyto-radiate" signals to the modules, i.e. at millimeter-wave carrier frequencies.Thanks to their low transmission loss and their high bandwidth, optical fiber distributionarchitectures represent a promising solution. The technique is referredto as the so-called "radio-over-fiber" approach whereby the analog radio signalwill be transported to the access point by an optical wave. The challenge herebyis the generation and modulation of an optical signal by a millimeter-wave radiosignal using preferably cost-efficient system components. The technique proposedherein is based on the use of mode-locked laser diodes which can generatesignals at very high frequencies under the condition of continuous current supply.Mode-locked laser diodes can be modulated both directly and externally. Thediodes employed in this work are based on so-called quantum dots (or quantumdashes); these are material structures which are themselves still subject to intensivephysical research. Signals at millimeter-wave frequencies (around 60 GHz)can easily be generated by such lasers. However, their frequency and phase stabilityis as yet limited. In the context of radio-over-fiber communication systems,these structures have not yet been studied in detail.In the course of this dissertation, several aspects are considered. A first systemstudy treats the basic properties of a system built from this type of laser source(available signal power, system noise figure, linearity etc.). A second study isdevoted to an investigation of propagation effects like dispersion, which considerablyinfluence the attainable transmission distances. An essential result of bothstudies is the importance of limiting the laser spectrum to a small number of lasermodes for an optimization of link gain, generated RF power, and system noisefigure. A third study deals with the limited frequency and phase stability whichturn out to be critical factors for transmission quality. The study of several generationsof quantum dot/dash lasers has revealed that the problems of frequencyand phase noise persist and cannot be solved using classical techniques involvinge.g. conventional phase-locked loops. In this dissertation, a solution is presentedwhich not only allows a more precise adjustment of the laser frequency (precisionin the order of Hz to kHz) than that given by the manufacturing process of thelaser (precision in the order of GHz), but also enables a stabilization of frequencyand phase.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

Surveillance after Colorectal Polypectomy : Comparison Between Japan and U.S.

Background: Recently, early detection and early treatment of the colorectal cancer have been enabled by the improvement of endoscopic diagnosis and introduction of new techniques. In Japan, although Japan Polyp Study is running, there is no standard strategy concerning the post-polypectomy colonoscopic surveillance yet. Post-polypectomy colonoscopic surveillance is so far entrusted to each institute or each gastroenterologist at present. Material and method To analyze the present states of the surveillance after polypectomy in Japan, we performed questionary survey and compared them with the results in U.S. and U.S.Multisociety Task Force on colorectal Cancer. A simple random sample of 132 doctors who engaged in a digestive organ disease in plural institutes was obtained. Result: Many doctors recommend surveillance every around 1 year regardless of the kind of the polyp. Doctors in Japan tend to recommend postpolypectomy colonoscopic surveillance more frequently than that recommended U.S. Multisociety Task Force on colorectal Cancer. Furthermore in all types of polyps except for 12 mm tubular adenoma with high grade dysplasia, the majority of doctors in Japan recommend post-polypectomy colonoscopic surveillance more frequently than American doctors. Significant difference was found in surveillance of hyperplastic polyp among doctors with 1 to 5 years experience and those with more than 6 years. Conclusion: It has been shown that surveillance intervals varies substantially in each doctor. The agreement of the surveillance program in Japan is necessary to standardize the strategy for the post-polypectomy surveillance of the colon

Utility and safety of a new uneven double-lumen sphincterotome in cases of difficult biliary cannulation.

Background:We investigated the utility and safety of a new uneven double-lumen sphincterotome in biliary cannulation in comparison with the conventional pancreatic guidewire (PGW) method.Methods:We retrospectively evaluated 119 patients who required PGW placement because of difficult biliary cannulation. Endoscopic retrograde cholangiopancreatography (ERCP) was performed using a conventional ERCP catheter or a new uneven double-lumen sphincterotome. The success rate of bile duct cannulation, the operation time of bile duct cannulation, and the incidence of post-ERCP pancreatitis (PEP) were evaluated.Results:Forty-four patients were treated with a new double-lumen sphincterotome (the new sphincterotome group) and 75 patients underwent conventional PGW placement (the conventional group). The success rate of bile duct cannulation was 39/44 (88.6%) in the new sphincterotome group and 63/75 (84.0%) in the conventional group (not significant). The total biliary cannulation time (from the reach to the papilla to the finish of biliary cannulation) was 16.0 (6.5-78) min in the new sphincterotome group and 26.0 (5-80) min in the conventional group (P < 0.01). The time from PGW placement to bile duct cannulation was 3.5 (0.3-57) min in the magictome group and 12.0 (1-65) min in the conventional group (P < 0.01). Hyperamylasemia was observed in 13/44 (29.5%) and 17/75 (22.7%), respectively (not significant). Five of 44 (11.3%) of the new sphincterotome group and 14/75 (18.7%) of the conventional group were diagnosed with PEP (not significant).Conclusion:A new double-lumen sphincterotome allows selective bile duct cannulation to be performed in a shorter time than the conventional PGW method

Endoscopic biliary ethanol ablation using a novel multi-hole balloon catheter: In vivo feasibility study in a swine model.

BackgroundMinimally invasive local treatment could be a good option for the treatment of extrahepatic cholangiocarcinoma (eCCA). This study aimed to evaluate the feasibility of a novel local treatment method, endoscopic biliary ethanol ablation (EA), in vivo using a swine model.MethodsThis study utilized a prototype of the newly developed multi-hole balloon catheter. The swine bile duct was ablated using this balloon via the same approach as the conventional endoscopic retrograde cholangiography procedure. The study outcomes included technical success, clinical success, and adverse events associated with endoscopic biliary EA.ResultsFourteen miniature pigs underwent endoscopic biliary EA. Technical success was achieved for all endoscopic EA procedures without any hindrance. All pigs were reared and followed up for a median 35-day period after the procedure. No change was observed in the bile duct wall in one case, in which sufficient contact was not achieved between the balloon and bile duct wall. Except for this case, stricture formation occurred at the site of ablation, where the epithelium was sloughed and necrosis with denaturation replaced the granulation tissue and fibrotic changes. The median length and depth of the ablation area were 17.05 and 2.21 mm, respectively. No adverse events were observed, except for the formation of bile duct strictures and sequelae associated with strictures.ConclusionsThis preliminary study was the first to report endoscopic biliary EA using a novel multi-hole balloon catheter, which demonstrated technical feasibility and potential for the treatment for eCCA