1,144 research outputs found
Intermodal Four-Wave-Mixing and Parametric Amplification in km-long Fibers
We theoretically and numerically investigate intermodal four-wave-mixing in
km-long fibers, where random birefringence fluctuations are present along the
fiber length. We identify several distinct regimes that depend on the relative
magnitude between the length scale of the random fluctuations and the
beat-lengths of the interacting quasi-degenerate modes. In addition, we analyze
the impact of polarization mode-dispersion and we demonstrate that random
variations of the core radius, which are typically encountered during the
drawing stage of the fiber, can represent the major source of bandwidth
impairment. These results set a boundary on the limits of validity of the
classical Manakov model and may be useful for the design of multimode
parametric amplifiers and wavelength converters, as well as for the analysis of
nonlinear impairments in long-haul spatial division multiplexed transmission
Ion-Exchanged Glass Waveguides with Low Birefringence for a Broad Range of Waveguide Widths
Optical communications networks require integrated photonic components with negligible polarization dependence, which typically means that the waveguides must feature very low birefringence. Recent studies have shown that waveguides with low birefringence can be obtained, e.g., by use of silica-on-silicon waveguides or buried ion-exchanged glass waveguides. However, many integrated photonic circuits consist of waveguides with varying widths. Therefore low birefringence is consequently required for waveguides having different widths. This is a difficult task for most waveguide fabrication technologies. We present experimental results on waveguide birefringence for buried silverâsodium ion-exchanged glass waveguides. We show that the waveguide birefringence of the order of 106 for waveguide mask opening widths ranging from 2 to 10 ÎŒm can be obtained by postprocessing the sample through annealing at an elevated temperature. The measured values are in agreement with the values calculated with our modeling software for ion-exchanged glass waveguides. This unique feature of ion-exchanged waveguides may be of significant importance in a wide variety of integrated photonic circuits requiring polarization independent operation
On the Performance of Digital Back Propagation in Spatial Multiplexing Systems
Nonlinear performance in spatial multiplexing systems is strongly determined by the interplay between differential mode delay, linear mode coupling, and Kerr nonlinearity. In this article we review and extend the analysis of different solution methods for the linear coupling operator in the coupled nonlinear Schrödinger equation for spatial multiplexed propagation. Numerical solution methods are compared for different operational regimes as determined by differential mode delay and linear mode coupling. Finally, we review and extend the study of digital methods to mitigate the Kerr nonlinearity for arbitrary levels of random linear mode coupling. For the first time, it is shown that in spatial multiplexing systems transmission performance can be improved by reducing the number of back propagated channels for non-negligible levels of differential mode delay
Multicore fiber scenarios supporting power over fiber in radio over fiber systems
We propose the integration of power over fiber in the next generation 5G radio access network front-haul solutions based on spatial division multiplexing with multicore fibers. The different architectures in both shared- and dedicated- core scenarios for power over fiber delivery and data signals are described. The maximum power to be delivered depending on the efficiencies of the different components is addressed as well as the limits of the delivered energy to avoid fiber fuse and non-linear effects. It is shown how those limits depend on high power laser linewidth, fiber attenuation, link length and fiber core effective area. The impairments related to non-linear effects, multicore fiber crosstalk and temperature are also theoretically analyzed. Experiments show there is no degradation of signal quality for feeding powers of several hundreds of milliwatts for both scenarios in 4-core multicore fibers. This study helps in designing future power by light delivery solutions in Radio over Fiber systems with multicore fibers.This work was supported in part by the Spanish Ministry of Science, Innovation and Universities, Directorate for Research and Innovation at Madrid region, and H2020 European Union programme under Grant RTI2018-094669-B-C32 and Grant Y2018/EMT-4892, and in part by FSE and 5G PPP Bluespace project Grant 762055
Spatially integrated erbium-doped fiber amplifiers enabling space-division multiplexing
L'augmentation exponentielle de la demande de bande passante pour les communications laisse prĂ©sager une saturation prochaine de la capacitĂ© des rĂ©seaux de tĂ©lĂ©communications qui devrait se matĂ©rialiser au cours de la prochaine dĂ©cennie. En effet, la thĂ©orie de lâinformation prĂ©dit que les effets non linĂ©aires dans les fibres monomodes limite la capacitĂ© de transmission de celles-ci et peu de gain Ă ce niveau peut ĂȘtre espĂ©rĂ© des techniques traditionnelles de multiplexage dĂ©veloppĂ©es et utilisĂ©es jusquâĂ prĂ©sent dans les systĂšmes Ă haut dĂ©bit. La dimension spatiale du canal optique est proposĂ©e comme un nouveau degrĂ© de libertĂ© qui peut ĂȘtre utilisĂ© pour augmenter le nombre de canaux de transmission et, par consĂ©quent, rĂ©soudre cette menace de «crise de capacité». Ainsi, inspirĂ©e par les techniques micro-ondes, la technique Ă©mergente appelĂ©e multiplexage spatial (SDM) est une technologie prometteuse pour la crĂ©ation de rĂ©seaux optiques de prochaine gĂ©nĂ©ration. Pour rĂ©aliser le SDM dans les liens de fibres optiques, il faut rĂ©examiner tous les dispositifs intĂ©grĂ©s, les Ă©quipements et les sous-systĂšmes. Parmi ces Ă©lĂ©ments, l'amplificateur optique SDM est critique, en particulier pour les systĂšmes de transmission pour les longues distances. En raison des excellentes caractĂ©ristiques de l'amplificateur Ă fibre dopĂ©e Ă l'erbium (EDFA) utilisĂ© dans les systĂšmes actuels de pointe, l'EDFA est Ă nouveau un candidat de choix pour la mise en Ćuvre des amplificateurs SDM pratiques. Toutefois, Ă©tant donnĂ© que le SDM introduit une variation spatiale du champ dans le plan transversal de la fibre, les amplificateurs Ă fibre dopĂ©e Ă l'erbium spatialement intĂ©grĂ©s (SIEDFA) nĂ©cessitent une conception soignĂ©e. Dans cette thĂšse, nous examinons tout d'abord les progrĂšs rĂ©cents du SDM, en particulier les amplificateurs optiques SDM. Ensuite, nous identifions et discutons les principaux enjeux des SIEDFA qui exigent un examen scientifique. Suite Ă cela, la thĂ©orie des EDFA est briĂšvement prĂ©sentĂ©e et une modĂ©lisation numĂ©rique pouvant ĂȘtre utilisĂ©e pour simuler les SIEDFA est proposĂ©e. Sur la base d'un outil de simulation fait maison, nous proposons une nouvelle conception des profils de dopage annulaire des fibres Ă quelques-modes dopĂ©es Ă l'erbium (ED-FMF) et nous Ă©valuons numĂ©riquement la performance dâun amplificateur Ă un Ă©tage, avec fibre Ă dopage annulaire, Ă ainsi quâun amplificateur Ă double Ă©tage pour les communications sur des fibres ne comportant que quelques modes. Par la suite, nous concevons des fibres dopĂ©es Ă l'erbium avec une gaine annulaire et multi-cĆurs (ED-MCF). Nous avons Ă©valuĂ© numĂ©riquement le recouvrement de la pompe avec les multiples cĆurs de ces amplificateurs. En plus de la conception, nous fabriquons et caractĂ©risons une fibre multi-cĆurs Ă quelques modes dopĂ©es Ă l'erbium. Nous rĂ©alisons la premiĂšre dĂ©monstration des amplificateurs Ă fibre optique spatialement intĂ©grĂ©s incorporant de telles fibres dopĂ©es. Enfin, nous prĂ©sentons les conclusions ainsi que les perspectives de cette recherche. La recherche et le dĂ©veloppement des SIEDFA offriront d'Ă©normes avantages non seulement pour les systĂšmes de transmission future SDM, mais aussi pour les systĂšmes de transmission monomode sur des fibres standards Ă un cĆur car ils permettent de remplacer plusieurs amplificateurs par un amplificateur intĂ©grĂ©.The exponential increase of communication bandwidth demand is giving rise to the so-called âcapacity crunchâ 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 âcapacity crunchâ. 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
Digital Back Propagation via Sub-band Processing in Spatial Multiplexing Systems
An advanced digital backward-propagation (DBP) method using a separate-channels approach (SCA) is investigated for the compensation of inter-channel nonlinearities in spatial- and wavelength-multiplexed systems. Compared to the conventional DBP, intra- and inter-mode cross-phase modulation can be efficiently compensated by including the effect of the inter-channel walk-off in the nonlinear step of the split-step Fourier method. We found that the SCA-DBP relaxes the step size requirements by a factor of 10, while improving performance by 0.8 dB for large walk-off and strong linear coupling. For the first time, it is shown that in spatial multiplexed systems transmission performance can be improved by sub-band processing of back propagated channels
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
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