130,698 research outputs found
Field-trial of an all-optical PSK regenerator/multicaster in a 40 Gbit/s, 38 channel DWDM transmission experiment
No full textThe performance of future ultra-long haul communication systems exploiting phase-encoded signals is likely to be compromised by noise generated during signal transmission. One potential way to mitigate such noise is to use Phase Sensitive Amplifiers (PSAs) which have been demonstrated to help remove phase as well as amplitude noise from phase-encoded signals. Recently, we showed that a PSA-based signal regenerator based on degenerate four-wave mixing can be implemented in a network-compatible manner in which only the (noisy) signal is present at the device input (black-box operation). The developed regenerator was also able to perform simultaneous wavelength conversion and multicasting, details/analysis of which are presented herein. However, this scheme was tested only with artificial noise generated in the laboratory and with the regenerator placed in front of the receiver, rather than in-line where even greater performance benefits are to be expected. Here, we address both theoretically and experimentally the important issue of how such a regenerator, operating for convenience in a multicasting mode, performs as an in-line device in an installed transmission fiber link. We also investigate the dispersion tolerance of the approach
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Numerical Analysis of Passively Mode-Locked Quantum-Dot Lasers With Absorber Section at the Low-Reflectivity Output Facet
No full textIn this paper, we present a theoretical study on the optimization of passively mode-locked quantum dot lasers based on an alternative cavity design. In particular, we investigate a geometry in which the saturable absorber is located near the low reflection facet of the chip (output facet). The investigation is carried out by means of a time-domain traveling wave numerical model for quantum-dot active medium for both the gain and absorbing sections. The analysis shows superior performance in terms of pulsewidth and peak power of devices based on the new geometry compared to devices based on the conventional geometry, where the saturable absorber is placed near the high reflectivity facet. The optimization relies on the enhanced bleaching of the saturable absorber when the latter is located near the output facet, which prevents the generation of colliding or self-colliding pulse effect
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
First demonstration of all-optical QPSK signal regeneration in a novel multi-format phase sensitive amplifier
No full textWe propose a novel black-box optical phase sensitive amplifier (PSA) configuration and describe its application to the regeneration of multi-level phase encoded signals. The concept is demonstrated with a 10 Gbaud quadrature phase shift keyed (QPSK) input
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Phase-encoded signal regeneration exploiting phase sensitive amplification
No full textWe discuss recent advances in phase-sensitive amplification technology and review its application to the regeneration of multi-level phase-encoded signals
Phase-encoded signal regeneration exploiting phase sensitive amplification
No full textWe discuss recent advances in phase-sensitive amplification technology and review its application to the regeneration of multi-level phase-encoded signals
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