1,721,009 research outputs found
Mode-selective fibre coupling using long range surface-plasmons
No full textA number of in-line single-mode fibre devices, including polarizers and fibre sensors, have been reported using long-range surface plasmons (LRSPs). In these devices, a side-polished fibre half-coupler block is coated with a thin metal layer supporting a LRSP mode that phase-matches to the fibre mode. This produces a resonance condition at which light is coupled from the fibre mode to the LRSP. In this paper, we explore the use of this resonance condition (which under certain conditions has high finesse) for mode-selective coupling into a dual-mode fibre; envisaged applications include to modal division multiplexing
Selective excitation of fibre-modes using surface plasmons
No full textExperimental and theoretical results are presented on a surface plasmon fiber device that provides selective excitation of individual modes in a dual-mode optical fiber. Using prism coupling to probe this device, good modal discrimination was obtained experimentally for the LP11 fiber mode. The LP11 modal discrimination, however, was found to be inherently limited by the field distribution characteristics of the dual-mode fiber. Applications are to fixed and tunable mode tap or couplers
Characteristics of chirped fibre gratings for dispersion compensation
No full textWe report a detailed measurement of the properties of a chirped fibre Bragg grating with respect to the amount of applied chirp. The results demonstrate the reflection and dispersion dependencies associated with any linearly chirped grating
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
Chirped fibre Bragg gratings fabricated using etched tapers
No full textWe have demonstrated a technique which is capable of controllably producing fibre Bragg gratings with arbitrary chirp profiles using etched tapers. Gratings with 4.8nm linear chirp have been produced. Nonlinearly chirped gratings have also been demonstrated
Complex grating structures with uniform phase masks based on the moving fiber-scanning beam technique
No full textWe present experimental results of complex grating structures fabricated with uniform phase masks by the moving fiber-scanning beam approach. Pure apodized gratings with side-mode-suppression levels in excess of 40 dB, self-apodized linearly chirped gratings, and phase shifted gratings with narrow-band transmission peaks have all been realized
Time delay characterization of a tunable chirped fibre grating for dispersion compensation
No full textThe development of chirped fibre grating filters for dispersion compensation in long fibre telecommunications links requires full and accurate amplitude and time delay characterisation of these devices. We have recently demonstrated a wavelength scanning interferometric technique with sub-picosecond time-delay and 3µm wavelength resolutions to provide such measurements. The system is based on an all-fibre Michelson interferometer. The reference arm of the interferometer is phase-modulated to generate an electric signal at the photodetector which carries the optical phase and amplitude information of the reflective fibre device under test, which is included in the signal arm. The amplitude response of the interferometer is directly proportional to the field reflection coefficient whilst the time delay is given by the derivative of the relative phase with respect to wavelength. A high wavelength resolution tunable laser source (HP8168A/C) is used in conjunction with a fully automated set-up to provide sub-picosecond resolution
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