Long continuously chirped fibre Bragg gratings for compensation of linear- and 3rd order-dispersion

For the first time long broadband chirped fibre Bragg gratings with a dispersion profile designed to compensate 3rd order-dispersion are presented. These results demonstrate how the increased demands for dispersion compensation at very high bit-rates can be met using chirped fibre Bragg grating

Phase-encoded duobinary transmission over non-dispersion shifted fibre links employing chirped grating dispersion compensators

High-bit-rate (10Gbit/s, 1.55µm) phase-encoded duobinary transmission over non-dispersion shifted fibre links employing chirped grating dispersion compensators is analysed. A reduced sensitivity to optical nonlinearities allows increased transmission powers and thus distance, 1700km compared to 1000km for the conventional NRZ-format. In addition for typical links around 700km an increased dispersion margin is observed, equivalent to ±60km compared with ±25km for the NRZ format

High self-selection of Ukrainian refugees into Europe: Evidence from Kraków and Vienna

Almost eight million Ukrainians have fled their country to escape the Russian full-scale invasion. To provide empirical evidence on how beneficiaries of temporary protection who reside in the immediate proximity of Ukraine differ from those who went further and reside in Western European countries, two large-scale rapid-response surveys were conducted in Kraków, Poland, and Vienna, Austria, in spring 2022. Data include information on socio-demographic characteristics, human capital, and return intentions of 472 and 1,094 adult Ukrainian refugees in Poland and Austria, respectively. Contributing to the growing empirical evidence on consistent assortative patterns in refugee inflows into Europe, our findings show that regularities in patterns of self-selection also occur in forced migration contexts where legal routes to safety apply. According to the analysed convenience sample, a tentative conclusion is that the further Ukrainian refugees moved to the West, the more self-selected they tend to be in the key dimensions of formal educational attainment, previous employment, language skills, and urbanity. Results indicate that willingness to stay in Kraków is significantly lower than willingness to remain in Vienna. This suggests that public financial support and living conditions, rather than diaspora networks, are decisive factors in shaping the decision to stay, move to another location or return to Ukraine. The aim to start a new life elsewhere may drive the motivation to choose a more distant destination instead of a neighboring country that allows to return rather quickly. Host countries should be aware of these specific characteristics of their refugee populations and adapt their integration policies accordingly

Enhancement on the generation of amplified spontaneous emission in thulium-doped silica fiber at 2 μ m

This paper investigates the generation of the amplified spontaneous emission (ASE) from thulium-doped silica fiber pumped at 1570 nm and 793 nm. The developed model provides the ASE spectral power as functions of the fiber length and the pump power under single-pass forward (SPF) and double-pass bi-directional (DPB) pumping schemes. A broadband ASE source generated by solving a set of rate and propagation equations for 1570 nm and 793 nm pumping transitions, and taking into account the influences of cross relaxation (CR) in both pump schemes. Our findings reveal that for 1570 nm pumping scheme, CR transition reduces the ASE generation. In addition, longer fluorescent lifetime increases the ASE power and reduces the pump power threshold. We numerically enhanced the generation of ASE broadband source from 1570 nm/1570 nm DPB pumping scheme. Our results show that 1570 nm/1570 nm DPB produces broadband ASE source with high slope efficiency and broader spectral bandwidth than that in SPF configuration. As a result, a 1570 nm/1570 nm DPB pump scheme is a suitable configuration to obtain higher power efficiency and a wider broadband source for the chosen thulium-doped silica fiber characteristics

Tales of the unexpected: the selection of British party leaders since 1963

Jeremy Corbyn’s election as Leader of the Labour Party in 2015 stunned observers and practitioners of British politics alike. In this article, we first outline a theoretical framework that purports to explain why political parties operating in parliamentary systems choose the leaders they do. We then examine 32 leadership successions involving five major British parties since 1963, and note that many of these were unexpected, in that they were triggered by unforeseen circumstances, such as the sudden death or resignation of the incumbent. Examining each party in turn, we briefly explain why the winners won and identify at least eight cases (a quarter of our sample) where a candidate widely expected to prevail at the outset was ultimately defeated by a ‘dark horse’, ‘second favourite’ or even ‘rank outsider’. Of these, Corbyn’s election in 2015 was the most unexpected and, consistent with the findings of studies of party leadership conventions in other parliamentary systems, namely Canada and Spain, suggests that ideological and policy concerns are sometimes more important than considerations of party unity and electability, especially when a leadership contest is dominated by party activists

Fibre Bragg gratings for dispersion compensation in optical communications

The main activities and recent developments towards the implementation of meter-long, high-performance fibre grating dispersion compensators in the Optoelectronics Research Centre, Southampton University are reviewed. Performance requirements of fibre-Bragg-gratings dispersion compensators and their impact on transmission systems will be discussed. We will report on the characteristics of continuously chirped FBGs capable of compensating linear and third-order dispersion over ~10nm bandwidth. Finally, system results using chirped FBGs as dispersion compensators will be given