1,721,019 research outputs found
Diode-pumped amplification of Q-switched AlGaAs diode laser to high power using fluoride fibre amplifier
No full textA diode-pumped, thulium-doped, fluorozirconate fibre amplifier has been used to amplify high-power pulses from a modulated AlGaAs diode laser at 805nm, using a 100mW single-stripe diode laser at 785nm as the pump source. Internal gains in excess of 18dB were observed in the small-signal regime. The greatest peak output power, observed for a launched pump power of 47mW, was 12.5W for pulses of 15ps duration driven at a repetition rate of 7MHz
High speed OFDM-CDMA optical access network.
Full text linkWe demonstrate the feasibility of a 16 × 3.75 Gb/s (60 Gb/s aggregate) Orthogonal frequency division multiplexing-code division multiple access passive optical network for next-generation access applications. 3.75 Gb/s PON channel transmission over 25 km single-mode fiber shows 0.1 dB dispersion and 0.9 dB crosstalk penalties. Advantages of the system include high capacity, enhanced spectral efficiency, coding gain, and networking functions such as increased security and single-wavelength operation
158µJ pulses from a single transverse mode, large mode-area EDFA
No full textWe report the amplification of 10pJ-100pJ, semiconductor diode pulses up to an energy of 158µJ and peak powers >100kW in a multi-stage fibre amplifier chain based on a single-mode, large mode-area erbium doped amplifier design. These results represent the highest single-mode pulse energy ever extracted from any doped fibre system
Diode-pumped amplification of a short pulse, high peak power AlGaAs diode lasers using a fluoride fibre amplifier
No full textA diode pumped, thulium-doped fluorozirconate fibre amplifier has been used to amplify high-power pulses from a modulated AlGaAs diode laser at 80Snm, using a 100mW single stripe diode laser at 785nm as the pump source. Internal gains of up to 19dB were observed for the average launched signal power in the small signal regime, while this was reduced to 16.4dB for average launched signal powers of -8.8dBm. A maximum output power of 12.SW was obtained from 15ps pulses, of incident power 2.1W, being driven at 7MHz so as to avoid saturation; thus showing a system gain of 7.8dB. When operating the amplifier towards saturation, 9.4W amplified output was obtained for 15ps pulses at 36MHz
First demonstration of OFDM ECDMA for low cost optical access networks.
Full text linkWe demonstrate for the first time to the best of our knowledge an analogue orthogonal frequency division multiplexing (OFDM) based electrical code division multiplexing access (ECDMA) passive optical network (PON) for next generation access applications. Advantages of the system include low cost, high capacity, and enhanced spectral efficiency. A proof-of-principle 16 QAM OFDM ECDMA PON downlink experiment is used to show the transmission of an aggregate data rate of 24.8 Gb/s within an eight-user system. Transmission is achieved over 25 km of single-mode telecommunications fiber (SMF) with negligible dispersion and crosstalk penalties
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
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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