Optical interferometry-based array of seafloor environmental sensors using a trans-oceanic submarine cable

Optical fiber–based sensing technology can drastically improve Earth observations by enabling the use of existing submarine communication cables as seafloor sensors. Previous interferometric and polarization-based techniques demonstrated environmental sensing over cable lengths up to 10,500 kilometers. However, measurements were limited to the integrated changes over the entire length of the cable. We demonstrate the detection of earthquakes and ocean signals on individual spans between repeaters of a 5860-kilometer-long transatlantic cable rather than the whole cable. By applying this technique to the existing undersea communication cables, which have a repeater-to-repeater span length of 45 to 90 kilometers, the largely unmonitored ocean floor could be instrumented with thousands of permanent real-time environmental sensors without changes to the underwater infrastructure

Electron Acceleration by Relativistic Surface Plasmons in Laser-Grating Interaction

The generation of energetic electron bunches by the interaction of a short, ultraintense (I>1019 W/cm2) laser pulse with "grating" targets has been investigated in a regime of ultrahigh pulse-to-prepulse contrast (1012). For incidence angles close to the resonant condition for surface plasmon excitation, a strong electron emission was observed within a narrow cone along the target surface, with energy spectra peaking at 5-8 MeV and total charge of ∼100 pC. Both the energy and the number of emitted electrons were strongly enhanced with respect to simple flat targets. The experimental data are closely reproduced by three-dimensional particle-in-cell simulations, which provide evidence for the generation of relativistic surface plasmons and for their role in driving the acceleration process. Besides the possible applications of the scheme as a compact, ultrashort source of MeV electrons, these results are a step forward in the development of high-field plasmonics

A Networking Comparison between Multicore Fiber and Fiber Ribbon in WDM-SDM Optical Networks

Spatial division multiplexing (SDM) represents a possible solution to face the continuous traffic growth. We compare: uncoupled fiber ribbons and strongly coupled-core multicore fibers. We compare them analyzing propagation and switching issues varying the SDM cardinality

Un'osmosi profonda tra mare e fiume

La ricerca è incentrata sull'ultimo tratto del fiume Tevere, in corrispondenza della sua foce. Questo luogo è caratterizzato da diversi tessuti edilizi e da diverse situazioni naturalistiche ed antropizzate, un luogo di grandi tensioni dinamiche ed evolutive. I metodi di rappresentazioni a disposizione sono in grado di raffigurare stadi di progressiva “entropia”, intesa come grado di “disordine” figurativo e strutturale, definito attraverso un'analisi comparativa di scala e conformazione dei singoli brani di tessuto urbano presi in esame. Sono così individuabili una serie di possibili letture definibili come: metafora generativa e metafora evoluzionistica. Volume realizzato con il finanziamento del Ministero dell'Istruzione dell'Università e della Ricerca – MIUR e con il cofinanziamento dell'Ateneo “La Sapienza”. Esito della ricerca nazionale PRIN “Piano di monitoraggio e riqualificazione dei bacini fluviali e lacustri italiani”, condotta negli anni 2004, 2005 e 2006 da tre sedi universitarie. Coordinamento scientifico di Roberto de Ruberti

Structured targets for advanced laser-driven sources

International audienceStructured targets offer great control over ultra-intense laser-plasma interaction, allowing the optimization of laser-target coupling for specific applications. By means of particle-in-cell simulations we investigated three applications in particular: high-order harmonic generation (HHG) with grating targets, enhanced target coupling with multilayer targets and the generation of intense laser-driven terahertz (THz) pulses with structured targets. The irradiation of a solid grating target at the resonance angle for surface plasmon excitation enhances the HHG with respect to flat targets. Multilayer targets consisting of solid foils coated with a very low-density near-critical layer lead to a strong laser absorption and hot electron production that can improve laser-driven ion acceleration. We also explored the generation of THz radiation showing how using either gratings or multilayer targets the emission can be strongly enhanced with respect to simple flat targets

Networking benefit of multi-subcarrier transceivers

We analyze the benefit of multi-subcarrier transceivers on two network topologies. We describe nonlinearities modeling challenges and demonstrate the existence of an optimal subcarrier symbol rate at network-level yielding average OSNR increase up to 0.7dB