Spatial Mode Division Multiplexing of Free-Space Optical Communications Using a Pair of Multiplane Light Converters and a Micromirror Array for Turbulence Emulation

Multi-plane light converters (MPLC) are a means of deconstructing a wavefront into constituent modes that are focused at specific spatial locations, and the reverse—that specific inputs result in controlled modal output. We have used a pair of MPLCs with 21 Hermite–Gaussian modes to represent a free-space optical connection. The effects of strong atmospheric turbulence (Cn2 = 10−13 m−2/3) are emulated using a micromirror array producing a time sequence of aberrating frames. The modal crosstalk between transmitter and receiver modes induced by the turbulence is presented by measuring the intensity in receiver channels for the same turbulence. Six receiver modes are used for optical communication channels with a rate of 137 Gbits/s displaying the benefits of single input multiple output (SIMO) operation for overcoming the deleterious effects of turbulence

Power-scaling of wavelength-flexible two-micron fibre sources

In this thesis we explore thulium doped silica fibre based sources, focusing on laser and amplified spontaneous emission behaviours. We analyse new ways of improving fibre cavity performances by first demonstrating a novel way of manufacturing doped fibres showing high pump absorption whilst retaining ease of use for cleaving and splicing. This new process offers a trade-off between circular and non-circular fibre geometries by maintaining advantages of both configurations. An implementation process on fibre drawing towers is detailed for future large scale production of highly circular active fibres with high mode scrambling, resulting in high pump absorption comparable, and potentially higher, to octagonal fibre. We then introduce a new way of improving fibre tip movement insensitivity in free-space feedback arms by utilising corner-cubes as reflective elements, with results showing transverse fibre tip movement of more than a millimetre in specific configurations whilst maintaining high feedback efficiency. Output power variation of less than 35% was demonstrated over a translation window of ±1.2mm in some cases.Exploiting the movement insensitive properties offered by a corner-cube, a tunable ring laser based on fibre tip movement and a Fabry-Perot etalon is demonstrated. Up to 5nm of quasi-continuous fine tuning is proven with a theoretical accuracy of 8pm/μm fibre tip movement and a linewidth lower than 1.5GHz is demonstrated. Potential for rapid wavelength scanning and for much broader tuning over a window of few tens of nm is proposed with further modifications of the experimental setup to allow wider fibre tip movement without feedback losses appearing.Focus is then centred on the broad tuning capabilities on thulium doped silica fibres and a CW laser source allowing tuning over more than 130nm in the 2μm band is described. Tuning is achieved by the use of a digital micro-mirror device (DMD) coupled with a diffraction grating, allowing further spectral shaping. Up to 8.5W of output power is displayed, pump power limited, with capabilities for multi-wavelength emission and spectral power density shaping by adjustment of the micro-mirror matrix reflective pattern. Modification of the system was explained in order to achieve different requirements, either by improving tuning range, accuracy or minimal line width.Utilising the fast dynamics of a doped fibre cavity, a cavity is built around an acousto-optic modulator to frustrate lasing in order to create a feedback tolerant pulsed amplified spontaneous emission (ASE) source. This source was designed to allow generation of a pulsed wavelength-controllable ASE via the use of a DMD coupled with a diffraction grating. A core-pumped setup is demonstrated, reaching tuning from 1860 to 1950nm and a cladding-pumped architecture is built for longer wavelengths generation to improve compatibility with amplifier stages. This source displayed tuning performances from 1940 to 2020nm with peak power of up to 1.5kW and pulses shorter than 100ns. Multi-waveband behaviour is demonstrated and output bandwidth is controlled through the DMD. A cladding-pumped amplification stage is described and amplification of the ASE output by 15dB, reaching up to 72W, pump limited, was demonstrated corresponding to peak powers of more than 5kW. Prospects for pumping of a ZGP OPO cavity with an ASE are discussed, detailing the potential benefits of utilising a bandwidth-adjustable ASE source for mid-infrared generatio

Wavelength-flexible thulium-doped fiber laser employing a digital micro-mirror device tuning element

We demonstrate a cladding-pumped thulium-doped fiber laser using a digital micromirror device based wavelength selection element. Tunability over 121nm was achieved with up to 8.4W of output power as well as multi-wavelength operatio

Alternative passive fiber coupling system based on multi-plane light conversion for satellite-to-ground communications

Global coverage of internet access is essential for digitalization in society, becoming a disruptive technology in industry, education or political participation for example. Satellite communications is a complementary approach to the terrestrial fiber network, which can provide world-wide coverage with few satellites in geostationary orbit or with low-earth-orbit constellations. Optical wavelengths offer multiple THz of available spectrum that can be used to connect satellites to the ground network with high-throughput links, solving the radiofrequency bandwidth bottleneck, without regulations. Cloud covereage and atmospheric turbulence are the main challenge in guaranteeing the same availability as in terrestrial fiber-based systems. While the former can be addressed by site diversity, for the latter, other mitigation strategies are required. Adaptive optics is a common approach to correct for atmospheric phase distortions and ensure stable fiber coupling. However, this approach requires a relatively complex active setup and therefore a collaboration between DLR Institute of Communications and Navigation and Cailabs has been formed to investigate alternative passive solutions for low-complexity ground stations. Coupling into multimode fibers does not require adaptive optics due to the large fiber core, however the coupled signal is distributed into multiple fiber-modes and is therefore incompatible with standard telecommunications components. Cailabs Multi-Plane Light Conversion (MPLC) technology overcomes this issue, selectively demultiplexing the fibermodes into single-mode fibers. Here, DLR's adaptive optics system and the MPLC technology in a turbulence-relevant environment for GEO communications are compared, investigating the advantages of the MPLC approach for compensating strong turbulence. This paper presents an overview of the measurement setup and analyzes the single-mode fibers outputs of the spatial demultiplexer and the measured phase-distortions from a wavefront sensor

SARS-CoV-2 Omicron Variant, Lineage BA.1, Is Associated with Lower Viral Load in Nasopharyngeal Samples Compared to Delta Variant

Objectives: High viral load in upper respiratory tract specimens observed for Delta cases might contribute to its increased infectivity compared to the other variant. However, it is not yet documented if the Omicron variant’s enhanced infectivity is also related to a higher viral load. Our aim was to determine if the Omicron variant’s spread is also related to higher viral loads compared to the Delta variant. Methods: Nasopharyngeal swabs, 129 (Omicron) and 85 (Delta), from Health Care Workers were collected during December 2021 at the University Hospital of Lyon, France. Cycle threshold (Ct) for the RdRp target of cobas® 6800 SARS-CoV-2 assay was used as a proxy to evaluate SARS-CoV-2 viral load. Variant identification was performed using a screening panel and confirmed by whole genome sequencing. Results: Herein, we showed that the RT-PCR Ct values in Health Care Workers sampled within 5 days after symptom onset were significantly higher for Omicron cases than Delta cases (21.7 for Delta variant and 23.8 for Omicron variant, p = 0.008). This difference was also observed regarding patient with complete vaccination. Conclusions: This result supports the studies showing that the increased transmissibility of Omicron is related to other mechanisms than higher virus excretion

Two-step strategy for the identification of SARS-CoV-2 variant of concern 202012/01 and other variants with spike deletion H69–V70, France, August to December 2020

International audienceWe report the strategy leading to the first detection of variant of concern 202012/01 (VOC) in France (21 December 2020). First, the spike (S) deletion H69-V70 (ΔH69/ΔV70), identified in certain SARS-CoV-2 variants including VOC, is screened for. This deletion is associated with a S-gene target failure (SGTF) in the three-target RT-PCR assay (TaqPath kit). Subsequently, SGTF samples are whole genome sequenced. This approach revealed mutations co-occurring with ΔH69/ΔV70 including S:N501Y in the VOC

L’Homme et son environnement : des lacs, des montagnes et des rivières

Ce recueil d'articles est destiné à saluer notre collègue André Marguet, qui a consacré une trentaine d'années de sa vie d'archéologue à l'étude et à la préservation des gisements immergés dans les lacs savoyards. Il regroupe deux douzaines de contributions originales qui abordent des questions variées liées à l'homme et à son environnement, entre lacs, montagnes et rivières. La diversité des sujets abordés témoigne des rencontres et des amitiés nouées par André et reflète assez bien ses thèmes de prédilection. Les textes rassemblés dans ce volume couvrent un vaste espace géographique au cœur de l'Europe occidentale, et s'éloignent ainsi largement des lacs alpins et jurassiens. Ils abordent un intervalle de temps étendu, de la Préhistoire récente jusqu'aux époques historiques, et donnent un bel aperçu de la diversité actuelle des objets, des questionnements et des méthodes de l'archéologie.Diese Sammlung ist ein Gruß an unseren Kollegen André Marguet, der an die 30 Jahre seiner archäologischen Tätigkeit der Erforschung und der Erhaltung der in den savoyischen Seen lagernden Fundstätten gewidmet hat. Die Sammlung umfasst zwei Dutzend Beiträge zu unterschiedlichen Themen, die den Menschen und seine Umwelt inmitten von Seen, Bergen und Flüssen betreffen. Die Vielfalt der Themen zeugt von Begegnungen und den Freundschaften, die André geknüpft hat, und gibt eine recht genaue Vorstellung von seinen Lieblingsthemen. Die Texte dieses Bandes decken ein weites Gebiet im Herzen Westeuropas und gehen auf diese Weise weit über die Seen der Alpen und des Jura hinaus. Sie betreffen einen langen Zeitraum, von der jüngeren Urgeschichte bis in die jüngeren geschichtlichen Epochen, und vermitteln ein Bild von der aktuellen Vielfalt der Artefakte, Fragestellungen und Methoden der Archäologie.This collection of articles is dedicated to our colleague André Marguet, who has spent some thirty years of his archaeological career dedicated to the study and preservation of the underwater sites in the lakes of Savoie. It brings together two dozen original papers that tackle various themes on man and his environment, including lakes, mountains and rivers. The variety of subjects attests the exchanges and friendships entered into by André and reflect his preferred subjects. The texts cover a vast geographic area of Western Europe, also straying far from the lakes of the Alps and Jura. They extend over a protracted period, from recent prehistory to the twentieth century, and offer a snapshot of the current state of affairs

Type I IFN immunoprofiling in COVID-19 patients

International audienceNo abstract availabl