1,721,037 research outputs found
Gain-shaped waterfilling is Quasi-optimal for Constant-pump Flattened-EDFA Submarine Links
No full textFor EDFA-amplified submarine links, we corroborate the results in1 by analytically deriving an approximate capacity-achieving distribution where power is allocated inversely to the EDFA gain
Modeling Nonlinear Interference with Sparse Raman-Tilt Equalization
Full text linkWe investigate the impact of accumulated stimulated Raman scattering (SRS) on the nonlinear interference (NLI) variance due to sparse gain-tilt equalization along the optical link. We propose simple modifications to analytical models available in the literature, such as the Gaussian noise (GN) or the enhanced Gaussian noise (EGN) models, for reliable NLI estimation in the presence of accumulated SRS. We additionally generalize closed-form expressions of the NLI variance in a GN framework to the new scenario. We validate the models through split-step Fourier method simulations showing the importance of including the gain-tilt equalization period in the model to preserve the accuracy. The proposed model is then used to provide insights on the interplay between the NLI and accumulated SRS
The Enhanced Gaussian Noise Model Extended to Polarization-Dependent Loss
Full text linkWe show how to extend the enhanced Gaussian noise (EGN) model to account for polarization-dependent loss (PDL) of optical devices placed along a fiber-optic link. We provide a comprehensive theory highlighting the relationships between the time, frequency, and polarization domains in the presence of fiber nonlinear Kerr effect and amplified spontaneous emission. We double-check the new model with split-step Fourier method (SSFM) simulations showing very good accuracy. The model can be efficiently exploited to estimate low values of outage probabilities induced by PDL with computational times orders of magnitude faster than the SSFM, thus opening new opportunities in the design of optical communication links
A State-Variable Approach to Submarine Links Capacity Optimization
No full textWe consider the capacity optimization of submarine links when including a realistic model of the gain-shaped constant-pump erbium doped fiber amplifiers (EDFA) with gain-shaping filters (GSF). While Perin et al. [1] numerically attacked this optimization for Constant-Signal (CS) amplified links, we extend the analysis also to constant power-spectral-density (CPSD) links, which mimic the way modern submarine links are gain-designed at cable assembly. Given the practical tolerances in GSF fabrication, the CS and CPSD approaches will be shown to essentially model the same link at large-enough pumps, but the CPSD approach yields a much simpler analysis. As in [1], we concentrate on a single spatial mode of a spatial division multiplexed (SDM) link at low EDFA pump power Pp, and thus consider only the impairments of amplified spontaneous emission noise. Here we adopt a novel semi-analytical approach which consists of fixing the inversion x1 of the first EDFA (the state-variable of the link) and analytically finding capacity C(x1) by searching over the x1-feasible input wavelength division multiplexed (WDM) PSD distributions. Then the optimum inversion x1 that maximizes C(x1) is numerically obtained. This approach enables us to get both approximate (for CS links) and exact (for CPSD links) capacity-maximizing WDM input distributions, which vary inversely with the EDFA gain profile. For CS links the optimal WDM allocation is called the gain-shaped water-filling. Other practical allocations are analyzed, such as the signal to noise ratio equalizing allocation (CSNR), and the constant input power (CIP) allocation which uses a flat WDM distribution. We find that, for typical submarine span attenuations around 10dB and when the link works at the optimal inversion x1, CIP and CSNR achieve essentially the same capacity as the optimal allocation. At sufficiently large pump Pp (> 30 mW) the optimal inversion x1 is such that the EDFA gain at 1538nm equals the span attenuation, for EDFA emission and absorption as in [1]. When span attenuations increase to 20dB, then we start seeing an advantage of the optimal allocation
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
A smartphone application for a citizen science project on seafood sustainable consumption
Full text linkNew Information and Communication Technologies (ICT) are playing a key role in Citizen Science outbreak, allowing a wider public participation. The increasingly availability of smartphone can be exploited as a tool for easy and quickly data collection.
The idea of the realisation of a smartphone App arises inside a Citizen Science project on sustainable consumption of seafood, “Il pesce giusto”. In fact, the overexploitation, the employment of destructive fishing practices and unsustainable techniques, as well as the widespread illegal fishing, have led to a loss of marine biodiversity and a food resources decline. A monitoring of marine resources consumption is now necessary.
Our aim has been to design an App that allows to monitor the sustainability of consumers’ purchases through different criteria: size, origin, production and seasonality of the fish species.
This tool can be practically utilised by citizen and can provide us information of the sustainability of marine resources sold in the markets
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
A model for the generalized droop formula
No full textWe provide a new analytical model that fully justifies the recently disclosed Generalized Droop Formula of the nonlinear signal-to-noise (SNR) ratio in very-long submarine links with power-mode amplifiers, and show its relation with the Gaussian-Noise model SNR
Scattering efficiency of thermally excited GaWBs in fibres for optical communications
No full textSimple formulas are proposed to quickly estimate the efficiency of thermally-excited guided acoustic wave Brillouin scattering in fibres for optical communications. The influence of the most important fibre parameters is shown, in particular the inverse dependence of the total scattering efficiency with the effective area
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