1,720,959 research outputs found
Degradations in balanced DPSK receivers
No full textWe discuss, both by simulation and experiment, the design of balanced differential phase-shift keying receivers. We study detector amplitude imbalance and phase imbalance, interferometer delay mismatch, interferometer. extinction, and laser frequency offset. The most critical impairment in a practical receiver is found to be a mismatch between laser frequency and interferometer phase, which directly impacts the interference quality
Robustness to laser frequency offset in direct-detection DPSK and DQPSK systems
No full textWe assess, both by measurement and simulation, the receiver performance degradation caused by frequency offsets between the optical source and the delay interferometer for nonreturn-to-zero (NRZ) and return-to-zero (RZ) differential-phase-shift-keying (DPSK) and differential-quadrature-phase-shift-keying (DQPSK) systems. We rind that NRZ- and RZ-DQPSK systems are about six times more sensitive to frequency offsets than NRZ- and RZ-DPSK systems operating at the same bit rate. We explain the reason for this behavior by means of eye aperture considerations
Impact of filtering on RZ-DPSK reception
No full textWe discuss the influence of optical and electrical filtering on the performance of beat-noise limited balanced and single-ended direct detection of return-to-zero differential phase-shift keying (DPSK). Our simulations, supported by 40-Gb/s measurements, show that balanced DPSK detection outperforms both its single-ended equivalent and ON-OFF keying by similar to2.7 dB, with higher gains at narrower optical filter bandwidths
Dependence of polarization-mode dispersion penalties on receiver characteristics
No full textWe measured the dependence of polarization-mode dispersion (PMD) penalty on receiver characteristics in an optically preamplified receiver using nonreturn-to-zero (NRZ) and return-to-zero (RZ) optical signals. The PMD-induced penalties were measured as a function of receiver electrical bandwidth at two different conditions: an optimized decision point and a fixed decision point. We also describe the measurement of the input polarization dependence of the PMD-induced penalty using polarization-scrambled signals. The observed penalty depends strongly on decision point and receiver electrical bandwidth in both NRZ and RZ signal formats
Receiver impact on first-order PMD outage
No full textSimulation and measurement show that the robustness of a transmission system to first-order polarization-mode dispersion (PMD) depends on the combination of modulation format and receiver characteristics. For beat-noise limited receivers of typical bandwidth, return-to-zero has greater PMD tolerance than non return-to-zero coding
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Variations on the Author
Get PDF“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
Get PDFWe 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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