12 research outputs found
Spatially integrated erbium-doped fiber amplifiers enabling space-division multiplexing
L'augmentation exponentielle de la demande de bande passante pour les communications laisse présager une saturation prochaine de la capacité des réseaux de télécommunications qui devrait se matérialiser au cours de la prochaine décennie. En effet, la théorie de l’information prédit que les effets non linéaires dans les fibres monomodes limite la capacité de transmission de celles-ci et peu de gain à ce niveau peut être espéré des techniques traditionnelles de multiplexage développées et utilisées jusqu’à présent dans les systèmes à haut débit. La dimension spatiale du canal optique est proposée comme un nouveau degré de liberté qui peut être utilisé pour augmenter le nombre de canaux de transmission et, par conséquent, résoudre cette menace de «crise de capacité». Ainsi, inspirée par les techniques micro-ondes, la technique émergente appelée multiplexage spatial (SDM) est une technologie prometteuse pour la création de réseaux optiques de prochaine génération. Pour réaliser le SDM dans les liens de fibres optiques, il faut réexaminer tous les dispositifs intégrés, les équipements et les sous-systèmes. Parmi ces éléments, l'amplificateur optique SDM est critique, en particulier pour les systèmes de transmission pour les longues distances. En raison des excellentes caractéristiques de l'amplificateur à fibre dopée à l'erbium (EDFA) utilisé dans les systèmes actuels de pointe, l'EDFA est à nouveau un candidat de choix pour la mise en œuvre des amplificateurs SDM pratiques. Toutefois, étant donné que le SDM introduit une variation spatiale du champ dans le plan transversal de la fibre, les amplificateurs à fibre dopée à l'erbium spatialement intégrés (SIEDFA) nécessitent une conception soignée. Dans cette thèse, nous examinons tout d'abord les progrès récents du SDM, en particulier les amplificateurs optiques SDM. Ensuite, nous identifions et discutons les principaux enjeux des SIEDFA qui exigent un examen scientifique. Suite à cela, la théorie des EDFA est brièvement présentée et une modélisation numérique pouvant être utilisée pour simuler les SIEDFA est proposée. Sur la base d'un outil de simulation fait maison, nous proposons une nouvelle conception des profils de dopage annulaire des fibres à quelques-modes dopées à l'erbium (ED-FMF) et nous évaluons numériquement la performance d’un amplificateur à un étage, avec fibre à dopage annulaire, à ainsi qu’un amplificateur à double étage pour les communications sur des fibres ne comportant que quelques modes. Par la suite, nous concevons des fibres dopées à l'erbium avec une gaine annulaire et multi-cœurs (ED-MCF). Nous avons évalué numériquement le recouvrement de la pompe avec les multiples cœurs de ces amplificateurs. En plus de la conception, nous fabriquons et caractérisons une fibre multi-cœurs à quelques modes dopées à l'erbium. Nous réalisons la première démonstration des amplificateurs à fibre optique spatialement intégrés incorporant de telles fibres dopées. Enfin, nous présentons les conclusions ainsi que les perspectives de cette recherche. La recherche et le développement des SIEDFA offriront d'énormes avantages non seulement pour les systèmes de transmission future SDM, mais aussi pour les systèmes de transmission monomode sur des fibres standards à un cœur car ils permettent de remplacer plusieurs amplificateurs par un amplificateur intégré.The exponential increase of communication bandwidth demand is giving rise to the so-called ‘capacity crunch’ expected to materialize within the next decade. Due to the nonlinear limit of the single mode fiber predicted by the information theory, all the state-of-the-art techniques which have so far been developed and utilized in order to extend the optical fiber communication capacity are exhausted. The spatial domain of the lightwave links is proposed as a new degree of freedom that can be employed to increase the number of transmission paths and, subsequently, overcome the looming ‘capacity crunch’. Therefore, the emerging technique named space-division multiplexing (SDM) is a promising candidate for creating next-generation optical networks. To realize SDM in optical fiber links, one needs to investigate novel spatially integrated devices, equipment, and subsystems. Among these elements, the SDM amplifier is a critical subsystem, in particular for the long-haul transmission system. Due to the excellent features of the erbium-doped fiber amplifier (EDFA) used in current state-of-the-art systems, the EDFA is again a prime candidate for implementing practical SDM amplifiers. However, since the SDM introduces a spatial variation of the field in the transverse plane of the optical fibers, spatially integrated erbium-doped fiber amplifiers (SIEDFA) require a careful design. In this thesis, we firstly review the recent progress in SDM, in particular, the SDM optical amplifiers. Next, we identify and discuss the key issues of SIEDFA that require scientific investigation. After that, the EDFA theory is briefly introduced and a corresponding numerical modeling that can be used for simulating the SIEDFA is proposed. Based on a home-made simulation tool, we propose a novel design of an annular based doping profile of few-mode erbium-doped fibers (FM-EDF) and numerically evaluate the performance of single stage as well as double-stage few-mode erbium-doped fiber amplifiers (FM-EDFA) based on such fibers. Afterward, we design annular-cladding erbium-doped multicore fibers (MC-EDF) and numerically evaluate the cladding pumped multicore erbium-doped fiber amplifier (MC-EDFA) based on these fibers as well. In addition to fiber design, we fabricate and characterize a multicore few-mode erbium-doped fiber (MC-FM-EDF), and perform the first demonstration of the spatially integrated optical fiber amplifiers incorporating such specialty doped fibers. Finally, we present the conclusions as well as the perspectives of this research. In general, the investigation and development of the SIEDFA will bring tremendous benefits not only for future SDM transmission systems but also for current state-of-the-art single-mode single-core transmission systems by replacing plural amplifiers by one integrated amplifier
Flattening Few Mode Fiber Laser Source Based on PMF and Loop Mirror in a Ring Cavity Resonator
Abstract:
A multi-wavelength source using a hybrid amplifier comprised of a Semiconductor Optical Amplifier (SOA) and an Erbium-doped fiber amplifier (EDFA) in a ring fiber laser set up is proposed. Multi-wavelength sources are less expensive and more efficient than deploying several laser diodes at different wavelengths. They are also compact, spend low energy, and emit low heat than multiple laser diode systems. A polarization maintaining fiber (PMF) and an interference comb filter are used in conjunction with the suggested few mode fiber laser source to create higer than 14 wavelength around -28 dBm at a SOA by current near 300 mA and a 980 nm pump power of 95 mW. This source is designed by a combined of EDFA and SOA presented in this report. By altering the birefringence of the ring cavity used as a loop mirror and changing the angle of the plates of the polarization controllers, the number of wavelengths produced may be managed. The suggested fiber laser operates at room temperature and has a constant channel spacing of 0.8 nm, making it appropriate for fiber communication and sensing applications
Beiträge zur Dispersionskompensation basierend auf der Modenkonversion in höhere Moden und der Ausbreitung dieser Moden in Lichtwellenleitern
Besides attenuation, dispersion is the major limiting factor in high data rate fiber optical transmission systems. Dispersion compensation techniques have to be deployed in order to increase the data bandwidth or the reach of fiber optical links. Typically fixed value dispersion compensators are used. However at channel bit rates of 40 GBit/s and beyond adjustable residual dispersion compensator modules (DCM) are needed to guarantee an error free transmission under changing environmental conditions. In this thesis dispersion techniques were investigated which exploit the special propagation properties of higher order modes in custom-designed optical fibers. After a short introduction of state-of-the-art dispersion techniques and their parameters (chapter 2) the modeling and calculation of propagation properties of a particular mode in an optical fiber with an arbitrary, rotation-symmetric refractive index profile is shown (chapter 3). A converter from the fundamental mode and back is needed in order to exploit the propagation properties of a higher order mode (HOM). In this work long-period gratings (LPG) were considered as mode converters (chapter 4) as they can excite selective and nearly lossless a higher order mode. The modeling und calculation of these gratings, based on the fiber calculation of chapter 3, is presented in the first part of chapter 4. Afterwards the manufacturing methods developed during this work are introduced. The spectral properties of realized long-period gratings are discussed and the influence of such factors as strain and temperature on tuning the mode conversion is shown. A dispersion compensator type utilizing only the waveguide dispersion of a certain mode in a custom few mode fiber (FMF) is the subject of chapter 5. The working principle, the fiber design process and first measurements of a realized HOM-DCM with almost completely coupling FMF-LPG are presented. Subsequently the principle of a novel dispersion compensator with an arbitrary dispersion function for a higher or the fundamental mode is explained. In chapter 6 another type of dispersion compensator is investigated consisting of equally distributed long-period gratings along an optical fiber. The fiber pieces between the gratings create a certain time delay between the fundamental mode and the considered higher order mode. It is shown in simulations and in an experiment, that by tuning the mode conversion of each grating and the optical phase relation between the two signal paths in each fiber piece this finite impulse filter structure is so adjusted to function as a tunable residual dispersion compensator
Roadmap of optical communications
© 2016 IOP Publishing Ltd. Lightwave communications is a necessity for the information age. Optical links provide enormous bandwidth, and the optical fiber is the only medium that can meet the modern society's needs for transporting massive amounts of data over long distances. Applications range from global high-capacity networks, which constitute the backbone of the internet, to the massively parallel interconnects that provide data connectivity inside datacenters and supercomputers. Optical communications is a diverse and rapidly changing field, where experts in photonics, communications, electronics, and signal processing work side by side to meet the ever-increasing demands for higher capacity, lower cost, and lower energy consumption, while adapting the system design to novel services and technologies. Due to the interdisciplinary nature of this rich research field, Journal of Optics has invited 16 researchers, each a world-leading expert in their respective subfields, to contribute a section to this invited review article, summarizing their views on state-of-the-art and future developments in optical communications
Some issues relevant to propagation of lightwave signals in optical fibers
Fiber optics is a promising technology that can enable the high bit rates and long spans that are on increasing demand. Although the fiber bandwidth is as large as several terahertz, there are several phenomena, related to both intrinsic fiber properties and characteristics of the state-of-the-art transmitters and receivers, which seriously degrade the performance of fiber communication systems, imposing limits on the transmission bandwidths and distances that can be achieved.
In this thesis, some of the issues affecting linear and nonlinear propagation in optical fiber will be theoretically and experimentally studied. Schemes for compensation of some of these phenomena or amelioration of their effects will be presented