417 research outputs found
Performance characterization of a novel DWDM all-optical SDN-like metro-access network
No full textThe demand for software-defined re-configurability is becoming one of the greatest issues for network providers also in the metro-access segment. Several numerical simulations have been performed to demonstrate the feasibility of an innovative architecture based on the application of software-defined networking (SDN) paradigm to the edge of the network
Evaluation of the absorption spectrum in quantum dots for efficient solar cells
No full textToday, possibility of photovoltaic efficiency increase with use of semiconductor quantum dots (QDs) in solid inorganic solar cells is a dynamic research field due to nanotechnology development and use of III-V and III-V nitride semiconductors (GaN or InGaN). Self-assembled quantum dots (SAQDs) growth in Stranski-Krastanov (SK) mode are very interesting nano-structures in order to achieve this goal. In this paper results derived by a FEM simulation analysis of absorption coefficient done on small zincblende InAs/GaAs and wurtzite InxGat_xN/lnyGat_yN (In content x > y) SAQDs are shown and related to possible use in solar cells
Future Scenarios for Software-Defined Metro and Access Networks and Software-Defined Photonics
No full textIn recent years, architectures, devices, and components in telecommunication networks have been challenged by evolutionary and revolutionary factors which are drastically changing the traffic features. Most of these changes imply the need for major re-configurability and programmability not only in data-centers and core networks, but also in the metro-access segment. In a wide variety of contexts, this necessity has been addressed by the proposed introduction of the innovative paradigm of software-defined networks (SDNs). Several solutions inspired by the SDN model have been recently proposed also for metro and access networks, where the adoption of a new generation of software-defined reconfigurable integrated photonic devices is highly desirable. In this paper, we review the possible future application scenarios for software-defined metro and access networks and software-defined photonics (SDP), on the base of analytics, statistics, and surveys. This work describes the reasons underpinning the presented radical change of paradigm and summarizes the most significant solutions proposed in literature, with a specific emphasis to physical-layer reconfigurable networks and a focus on both architectures and devices
Passive Optical Access Networks: State of the Art and Future Evolution
No full textIn the very last years, optical access networks are growing very rapidly, from both the network operators and the research interests points of view. Fiber To The Home (FTTH) is already a reality in plenty of real contexts and there has been a further stimulus to the proposal of new solutions and the investigation of new possibilities, in order to optimize network performance and reduce capital and operational expenditure. A complete and systematic overview of passive optical access networks is presented in this paper, concerning both the hot research topics and the main operative issues about the design guidelines and the deployment of Passive Optical Networks (PON) architectures, nowadays the most commonly implemented approach to realize optical fiber links in the access networks. A comparison of advantages and disadvantages of different multiplexing techniques is discussed, with specific reference to WDM-based networks, almost universally considered as the enabling technology for future proof bandwidth requirements. An exhaustive summary is also given about the-state-of-the-art of modulation and encoding techniques recently proposed by the scientific community, as well as the open challenges (such as colorless and coolerless ONUs) for telecom companies and international standardization compliance
Strengthening of Existing Timber Beams with NSM CFRP Plates
No full textIn order to reduce the environmental impact of the construction industry, retrofitting/strengthening of existing buildings should be preferred to demolition and re-construction. In most cases, retrofitting should not significantly alter the geometry and aspect of the member and at the same time increase its strength and/or stiffness. For buildings including timber structural members, specific techniques are needed to reach these goals. Within this context, the near surface mounted (NSM) strengthening technique is a possible solution to strengthen timber members without changing their aspect/geometry. This technique consists of bonding a reinforcing profile into a groove cut within the member surface. Often, reinforcing profiles are made of fiber-reinforced polymer (FRP) composites bonded with epoxy resin, since they have a high strength-to-weight ratio and do not suffer from corrosion. In this paper, an experimental campaign is conducted to study the bending behavior of timber beams strengthened with NSM carbon FRP (CFRP) plates applied with an epoxy resin. Four direct-shear tests are first conducted on CFRP-timber joints. Peak loads and interfacial slips are obtained. Then, three three-point bending tests are performed to assess the bending capacity of the strengthened members. Load-deflection curve, peak load, and failure mode of the specimens are provided and discussed
Recent Advances in Gas and Chemical Detection by Vernier Effect-Based Photonic Sensors
No full textRecently, the Vernier effect has been proved to be very efficient for significantly improving the sensitivity and the limit of detection (LOD) of chemical, biochemical and gas photonic sensors. In this paper a review of compact and efficient photonic sensors based on the Vernier effect is presented. The most relevant results of several theoretical and experimental works are reported, and the theoretical model of the typical Vernier effect-based sensor is discussed as well. In particular, sensitivity up to 460 μm/RIU has been experimentally reported, while ultra-high sensitivity of 2,500 μm/RIU and ultra-low LOD of 8.79 × 10−8 RIU have been theoretically demonstrated, employing a Mach-Zehnder Interferometer (MZI) as sensing device instead of an add drop ring resonator
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