1,721,010 research outputs found
Next generation 50G PON flexible transmitters based on directly modulated VCSELs
Full text linkWe consider long-wavelength vertical cavity surface emitting lasers (VCSELs) directly modulated with discrete multitone (DMT) signals as a very promising solution for implementing energy-efficient transmitters for 50G passive optical networks (PONs). Two scenarios based on single sideband and dual sideband modulation are taken into account. Preliminary experimentation with already available short-cavity VCSELs operating in the third window is presented to show the PON performance as a function of the accumulated chromatic dispersion and of the received power. Experimental results are also used to validate a simulation tool, which is further used to provide the performance evaluation of transmitters based on next-generation short cavity VCSELs with higher bandwidth (up to 20 GHz), operating in the O band. Thanks to its water-filling nature, DMT is demonstrated to enable PON flexibility: in fact, considering the statistics regarding a commercially deployed PON, a significant increase of the maximum aggregated capacity is provided, optimizing the PON resource usage with respect to the losses and dispersion impairments
Flexible transmitters based on directly modulated VCSELs for next-generation 50G passive optical networks
Full text linkDiscrete multitone (DMT) modulation, due to its water-filling nature, is proposed to enable flexibility in passive optical networks (PONs), optimizing the PON resource usage. The use of DMT signals to directly modulate long-wavelength vertical-cavity surface-emitting lasers (VCSELs) can provide energy-efficient transmitters for 50G PONs. First, we present preliminary experimental measures employing both single-sideband and dual-sideband DMT modulation with already available short-cavity VCSELs operating in the third window to study the PON performance as a function of the accumulated chromatic dispersion and of the received power. The experimental results are then compared with simulations, demonstrating the effectiveness of the developed simulation tool. Then we study the performance of DMT-modulated transmitters based on next-generation short-cavity VCSELs with higher bandwidth (up to 20 GHz) operating in the O-band, evaluating their chromatic dispersion resilience. Finally, considering the statistics of a commercially deployed PON, we demonstrate that DMT modulation, providing link adaptation, offers a significant increase in the total aggregated capacity compared to a single-carrier-based fixed-rate PON, optimizing the PON resource usage with respect to the available power budget and the dispersion impairments
SOA-based loss-less switch nodes for Tb/s multicarrier Transmission
No full textLoss-less nodes based on semiconductor optical amplifiers to enable add/drop functionalities are studied in order to preserve the traffic throughput when adopting high-capacity multicarrier signal formats in metropolitan area networks
Add-Drop Lossless Switch Node in Multi-Hop Multi-Tb/s Metropolitan Area Networks
No full textThe effect of SOA-based MAN node crossing on DMT high-capacity transmission is experimentally evaluated. A capacity of more than 50 Gb/s per channel is demonstrated for a multi-hop multi-channel transmission up to 116 km SSMF
Impact of SOA-Based Add-Drop Switch Nodes on High-Capacity Multicarrier Transmission for Metro-Access Networks
No full textInternet-generated traffic growth is forcing the development of new low-cost solutions in metropolitan area networks (MANs), in particular in the transceiver and network node architectures. Semiconductor optical amplifier (SOA)-based wavelength blockers can be used as fundamental building blocks to add and drop optical channels in the node architecture of several network hierarchical levels. Even if its employment is advantageous in terms of costs and amplification bandwidth, the SOA can operate in a nonlinear regime. This work analyzes the impact of SOA-based node crossing on high-capacity discrete multitone (DMT) signals. In order to properly evaluate the interplay between optical channels and SOA self-gain modulation, both external and direct modulations are considered. Dual-sideband (DSB) and single-sideband (SSB) DMT variants are taken into account, showing no significant difference in the impact of SOA crossing for external modulation of a DFB laser. On the other hand, an important effect of subcarrier suppression arises on DSB DMT direct modulation of a vertical cavity surface emitting laser (VCSEL), less consistent for SSB DMT direct modulation. The analysis allowed to properly choose the bias current for the SOA employed in an experimental setup used to evaluate the transmission performance in a MAN scenario including add-drop lossless switch nodes. The experimental results demonstrate that a target capacity of more than 50 Gb/s per channel can be achieved in a 116-km MAN network composed of an SOA-based metro-access node and two metro-core aggregators, considering the transmission of three 25-GHzspaced DMT channels
Mb4.1-beyond 50 Gb/s directly-modulated long-wavelength vcsels for next-gen access network (invited)
No full textThe employment of long-wavelength directly-modulated VCSELs for applications in next-generation access networks is proposed. Suitable simulations are shown in case of DMT modulation and SSB filtering, demonstrating the capabilities of LW-VCSEL for future 50-Gb/s access networks
Coexistence of OTN and VCSEL-based DMT Channels for Multi-Tb/s Transmission in Metropolitan Area Networks
No full textWe demonstrate the coexistence of 100G-200G OTN channels with a novel transmitter technology based on directly modulated VCSELs exploiting DMT. Multi-Tb/s transmission is achieved in links typical of the metro network
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
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