1,721,032 research outputs found
Space-Division Multiplexing
No full textFiber-based optical communication networks are reaching a point where the capacity required on a single link can significantly exceed the capacity of a single-mode fiber, and at the same time conventional network architectures can no longer be scaled cost-effectively. Space-division multiplexing (space-division multiplexing (SDM)) addresses the capacity bottleneck imposed by the use of single-mode fibers within a completely new approach that relies on new fiber types, optical amplifiers, and optical switches capable of supporting multiple spatial channels. The aim of this chapter is, on one hand, to provide an overview of the components that are necessary for the implementation of SDM transmission and, on the other hand, to review the modeling of the main propagation effects that occur in multimode and multicore fibers. The chapter also includes a description of the techniques that are used in SDM transmission experiments and an update on transmission records reported from around the globe. The chapter ends with the description of potential architectures supporting SDM networks
Measurement of Propagation Constants of Graded Index Multi-mode Fiber Using Rayleigh Backscattered Light
No full textWe measure the distributed differential group delay and effective refractive index difference between all 9 mode groups of a graded index multi-mode fiber using optical frequency domain reflectometry by cross correlating Raleigh backscatter signals. (C) 2021 The Author(s
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
Stokes-Space Analysis of Modal Dispersion of SDM Fibers with Mode-Dependent Loss: Theory and Experiments
Full text linkSignal propagation in Space-Division Multiplexed (SDM) systems in the linear regime is dominated by the effects of modal dispersion (MD) and mode-dependent loss (MDL). While multiple models have been proposed for characterizing these phenomena separately or to study the effect of MD on MDL, the effect of MDL on the system MD has never been analyzed. In this article, we report such an analysis, where the inclusion of MDL is accounted for by introducing a complex MD vector . We show that the signal delay spread, quantified by the duration of the intensity impulse response function, is not affected by the presence of MDL, and its functional dependence on remains the same as in the absence of MDL (in which case is a real-valued vector). The model, which represents SDM systems operating in the regime of strong coupling between modes, is validated by comparison with experimental data
Use of Optical Coherent Detection for Environmental Sensing
Full text linkWe discuss the use of the fiber channel transfer matrix extracted from a digital coherent receiver for environmental sensing. We show that the polarization rotation vector describing the unitary part of the matrix is highly sensitive to perturbations affecting the optical fiber link. This vector can be readily extracted from the time-dependent transfer matrix reconstructed by the coherent receiver during system operation and may serve as an effective observable to monitor environmental changes
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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