1,720,975 research outputs found
Programmable transmission systems using coherent detection enabling multi-Tb/s interfaces for IT-communications convergence in optical networks
No full textThe information technologies (ITs)-communications infrastructure convergence is key to future optical networks for achieving an automated orchestration of IT, optical and cloud resources. To cope with this challenge, transmission systems need to be agile, programmable, and capable of transmitting large amounts of data, while covering data center and metropolitan networks. This work addresses transmission solutions using coherent detection combined with either direct or external modulation, with special focus on flexible, high capacity and cost/energy-efficient systems. The proposed technological solutions are evaluated in terms of throughput, and programmability and interaction with the control plane
Preliminary Assessment of Photonic Solutions Based on C-Band VCSELs for Multi-Tb/s Metro Networks
Full text linkC-band InP vertical cavity surface emitting laser (VCSEL) exploitation can be appealing also for high-capacity transmission over hundreds of kilometres. Long-wavelength VCSELs can represent an alternative solution for the development of transmitters with reduced cost, power consumption and footprint by adopting direct modulation (DM) and single sideband (SSB) discrete multitone (DMT) modulation to achieve dense wavelength
division multiplexing (WDM) granularity. Due to numerous hops between nodes inside metropolitan area networks the effect of filtering can severely impact the transmission performance. We present preliminary experimental assessments of DM VCSEL sources with multi-carrier modulation formats, for more than 50 Gb/s per-channel transmission to target a metro network including nodes, handling 25-GHz granularity
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Upcoming applications driving the design of next-generation metro area networks: Dealing with 5G backhaul/fronthaul and edge-cloud computing
No full textThis article provides insight on two of the most relevant applications driving the design of the future MAN: the implementation of 5G by means of C-RAN (Cloud - Radio Area Network) and the deployment of edge computing. The work addresses important questions such as the target latency budget for future MANs, the target bandwidth requirements for 2020-2030 induced by 5G midhaul and fronthaul traffic, and describes how optical and electronics layers can co-operate to meet the QoS targets of C-RAN and edge computing traffic. In the process, we identify the key architectural elements to meet the challenges of these applications in a cost-effective way
All-optical aggregation and distribution of traffic in large metropolitan area networks using multi-Tb/s S-BVTs
Full text linkCurrent metropolitan area network architectures are based on a number of hierarchical levels that aggregate traffic toward the core at the IP layer. In this setting, routers are interconnected by means of fixed transceivers operating on a point-to-point basis where the rates of transceivers need to match. This implies a great deal of intermediate transceivers to collect traffic and groom and send it to the core. This paper proposes an alternative scheme based on sliceable bandwidth/bitrate variable transceivers (S-BVTs) where the slice-ability property is exploited to perform the aggregation of traffic from multiple edges n-to-1 rather than 1-to-1. This approach can feature relevant cost reductions through IP offloading at intermediate transit nodes but requires viable optical signal-to-noise ratio (OSNR) margins for all-optical transmission through the network. In this work, we prove through simulation the viability and applicability of this technique in large metro networks with a vertical-cavity-surface-emitting laser-based S-BVT design to target net capacities per channel of 25, 40, and 50 Gb/s. The study reveals that this technology can support most of the paths required for IP offloading after simulation in a semi-synthetic topology modeling a 20-million-inhabitant metropolitan area. Moreover, OSNR margins enable the use of protection paths (secondary disjoint paths) between the target node and the core much longer than primary paths in terms of both the number of intermediate hops and kilometers
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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