54 resultados para Amplifiers (Electronics)


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We numerically demonstrate the feasibility of return-to-zero differential phase-shift keying transmission at 80 Gbit/s channel rate using cascaded in-line semiconductor optical amplifiers.

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We report a theoretical study and simulations of a novel fiber-spin tailoring technique to suppress the polarization impairments, namely polarization mode dispersion and polarization dependent gain (PDG), in fiber Raman amplifiers. Whereas use of depolarizer or multiplexing pump laser diodes with a final degree of pump polarization of 1% for periodically spun fiber results in PDG of about 0.3 dB, we demonstrate that application of just a two-section fiber (where the first part is short and has no spin, and the second one is periodically spun) can reduce the PDG to as low as below 0.1 dB.

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We report on a theoretical study of polarization impairments in periodically spun fiber Raman amplifiers. Based on the Stochastic Generator approach we have derived averaged equations to calculate polarization dependent gain and mean-square gain fluctuations. We show that periodically spun fiber can work as a Raman polarizer but it suffers from increased polarization dependent gain and gain fluctuations. Unlike this, application of a depolarizer can result in suppression of polarization dependent gain and gain fluctuations. We demonstrate that it is possible to design a new fiber Raman polarizer by combining a short fiber without spin and properly chosen parameters and a long periodically spun fiber. This polarizer provides almost the same polarization pulling for all input signal states of polarization and so has very small polarization dependent gain.

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We have reduced signal-signal four-wave mixing crosstalk in a fiber optical parametric amplifier (OPA) by using a short nonlinear fiber for the gain medium and a high-power pump. This allowed us to obtain less than 1 dB penalty for amplification of 26 dense wavelength-division multiplexed (WDM) channels modulated at 43.7Gb/s return to zero-differential phase-shift keying, with the OPA placed between transmitter and receiver. We then used the same OPA in several different roles for a long-haul transmission system. We did not insert the OPA within the loop, but investigated this role indirectly by using equivalent results for small numbers of loop recirculations. We found that standard erbium-doped fiber amplifiers currently hold an advantage over this OPA, which becomes negligible for long distances. This paper shows that at this time OPAs can handle amplification of WDM traffic in excess of 1 Tb/s with little degradation. It also indicates that with further improvements, fiber OPAs could be a contender for wideband amplification in future optical communication networks.

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We investigate to what extent the unique features of OPAs (large bandwidths, 0 dB noise figure, phase conjugation, signal regeneration) can be combined and exploited in future long-haul communication networks. Network PMD can complicate the use of phase-sensitive amplification.

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A detailed experimental characterization of the transition process of an initially Gaussian pulse to the asymptotic self-similar parabolic solution in optical fibre amplifiers operating in the normal dispersion regime is performed.

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Whilst target costing and strategic management accounting (SMA) continue to be of considerable interest to academic accountants, both suffer from a relative dearth of empirically based research. Simultaneously, the subject of economic value added (EVA) has also been the subject of little research at the level of the individual firm.The aim of this paper is to contribute to both the management accounting and value based management literatures by analysing how one major European based MNC introduced EVA into its target costing system. The case raises important questions about both the feasibility of cascading EVA down to product level and the compatibility of customer facing versus shareholder focused systems of performance management. We provide preliminary evidence that target costing can be used to align both of these perspectives, and when combined with other SMA techniques it can serve as " the bridge connecting strategy formulation with strategy execution and profit generation" ( Ansari et al., 2007, p. 512). © 2012 Elsevier Ltd.

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Case law report - online

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Links the concept of market-driven business strategies with the design of production systems. It draws upon the case of a firm which, during the last decade, changed its strategy from being “technology led” to “market driven”. The research, based on interdisciplinary fieldwork involving long-term participant observation, investigated the factors which contribute to the successful design and implementation of flexible production systems in electronics assembly. These investigations were conducted in collaboration with a major computer manufacturer, with other electronics firms being studied for comparison. The research identified a number of strategies and actions seen as crucial to the development of efficient flexible production systems, namely: effective integration of subsystems, development of appropriate controls and performance measures, compatibility between production system design and organization structure, and the development of a climate conducive to organizational change. Overall, the analysis suggests that in the electronics industry there exists an extremely high degree of environmental complexity and turbulence. This serves to shape the strategic, technical and social structures that are developed to match this complexity, examples of which are niche marketing, flexible manufacturing and employee harmonization.

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Small indigenous manufacturers of electronic equipment are coming under increasingly severe pressure to adopt a strong defensive position against large multinational and Far Eastern companies. A common response to this threat has been for these firms to adopt a 'market driven' business strategy based on quality and customer service, rather than a 'technology led' strategy which uses technical specification and price to compete. To successfully implement this type of strategy there is a need for production systems to be redesigned to suit the new demands of marketing. Increased range and fast response require economy of scope rather t ban economy or scale while the organisation's culture must promote quality and process consciousness. This paper describes the 'Modular Assembly Cascade' concept which addresses these needs by applying the principles of flexible manufacturing (FMS) and just in time (,JlT) to electronics assembly. A methodology for executing the concept is also outlined. This is called DRAMA (Design Houtirw !'or· Adopting Modular Assembly).

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Information technology companies are having to broaden their overall strategic view in deference to the premise that it is better to be market-driven than technology-led. Cost and technical performance are no longer the only considerations, as quality and service now demand equal recognition. The production of a high volume single item has given way to that of low volume multiple items, which in turn requires some modification of production systems and brings flexible manufacturing, Just-in-Time production and total quality control into sharper focus for the achievement of corporate objectives.

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Strategic sourcing has increased in importance in recent years, and now plays an important role in companies’ planning. The current volatility in supply markets means companies face multiple challenges involving lock-in situations, supplier bankruptcies or supply security issues. In addition, their exposure can increase due to natural disasters, as witnessed recently in the form of bird flu, volcanic ash and tsunamis. Therefore, the primary focus of this study is risk management in the context of strategic sourcing. The study presents a literature review on sourcing based on the 15 years from 1998–2012, and considers 131 academic articles. The literature describes strategic sourcing as a strategic, holistic process in managing supplier relationships, with a long-term focus on adding value to the company and realising competitive advantage. Few studies discovered the real risk impact and status of risk management in strategic sourcing, and evaluation across countries and industries was limited, with the construction sector particularly under-researched. This methodology is founded on a qualitative study of twenty cases across Ger-many and the United Kingdom from the construction sector and electronics manufacturing industries. While considering risk management in the context of strategic sourcing, the thesis takes into account six dimensions that cover trends in strategic sourcing, theoretical and practical sourcing models, risk management, supply and demand management, critical success factors and the strategic supplier evaluation. The study contributes in several ways. First, recent trends are traced and future needs identified across the research dimensions of countries, industries and companies. Second, it evaluates critical success factors in contemporary strategic sourcing. Third, it explores the application of theoretical and practical sourcing models in terms of effectiveness and sustainability. Fourth, based on the case study findings, a risk-oriented strategic sourcing framework and a model for strategic sourcing are developed. These are based on the validation of contemporary requirements and a critical evaluation of the existing situation. It contemplates the empirical findings and leads to a structured process to manage risk in strategic sourcing. The risk-oriented framework considers areas such as trends, corporate and sourcing strategy, critical success factors, strategic supplier selection criteria, risk assessment, reporting, strategy alignment and reporting. The proposed model highlights the essential dimensions in strategic sourcing and guides us to a new definition of strategic sourcing supported by this empirical study.

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A detailed experimental characterization of the transition process of an initially Gaussian pulse to the asymptotic self-similar parabolic solution in optical fibre amplifiers operating in the normal dispersion regime is performed.