Enabling multipath optical routing with hybrid differential delay compensation

Historically, Internet traffic has been routed over the shortest path: that was convenient for best-effort data traffic, but it is not always suitable for today’s scenario where applications can require bandwidth higher than what is available in a single link, even when provided by an optical wavelength-channel. Multi-path (MP) routing is a network functionality that provides more capacity, reduces the probability of link congestion and increases the availability of the transport service. This paper elaborates on techniques to mitigate the differential delay in all optical networks, recognized as the main problem of multi-path (MP) routing. This work shows how hybrid differential delay compensation (H-DDC) can greatly reduce the use of expensive reconstruction buffers in all optical networks implementing MP optical routing. A novel mixed integer linear programming formulation is proposed for the novel wavelength + H-DDC assignment problem: distributed fiber delay lines (FDL)s combined with electronic reconstruction buffers collocated at optical regeneration points. Numerical results based on commercially available (and rack mountable) FDLs demonstrate the effectiveness of H-DDC in medium size transport networks

Competition between electric field and magnetic field noise in the decoherence of a single spin in diamond

We analyze the impact of electric field and magnetic field fluctuations in the decoherence of the electronic spin associated with a single nitrogen-vacancy (NV) defect in diamond by engineering spin eigenstates protected either against magnetic noise or against electric noise. The competition between these noise sources is analyzed quantitatively by changing their relative strength through modifications of the environment. This study provides significant insights into the decoherence of the NV electronic spin, which is valuable for quantum metrology and sensing applications.Comment: 8 pages, 4 figures, including supplementary information

Deep Learning-based Traffic Prediction for Network Optimization

In recent years, researchers realized that the analysis of traffic datasets can reveal valuable information for the management of mobile and metro-core networks. That is getting more and more true with the increase in the use of social media and Internet applications on mobile devices. In this work, we focus on deep learning methods to make prediction of traffic matrices that allow us to proactively optimize the resource allocations of optical backbone networks. Recurrent Neural Networks (RNNs) are designed for sequence prediction problems and they achieved great results in the past years in tasks like speech recognition, handwriting recognition and prediction of time series data. We investigated a particular type of RNN, the Gated Recurrent Units (GRU), able to achieve great accuracy (<7.4 of mean absolute error). Then, we used the predictions to dynamically and proactively allocate the resources of an optical network. Comparing numerical results of static vs dynamic allocation based on predictions, we can estimate a saving of 66.3% of the available capacity in the network, managing unexpected traffic peaks

SLA Formulation for Squeezed Protection in Elastic Optical Networks Considering the Modulation Format

In spectrum-sliced elastic optical path networks (SLICE), the lightpath bandwidth is variable, and the virtual topology overlay on a physical topology shall be designed to optimize the spectrum utilization. Under static traffic, SLICE networks are typically designed through a mixed integer linear programming (MILP) with the aim of minimizing the spectrum utilization. In this paper, a new MILP formulation for protection in SLICE networks is proposed, which uses the concept of bandwidth squeezing and grooming to guarantee a minimum agreed bandwidth for each source–destination pair in the surviving bandwidth. The route for each demand on the physical topology is determined by balance equations together with physical layer constraints in the formulation, so that no pre-calculated routes are required and the modulation format of each established lightpath may be chosen with enough quality of transmission and to save network spectrum. Therefore, the proposed formulation jointly solves the virtual topology design and physical topology design problems. The first results evaluate the effectiveness of the MILP formulation for two small networks when connections are under different service-level agreement (SLA) requirements and are provisioned by an appropriate protection scheme and different modulation formats. Due to the NP-hard nature of the proposed MILP formulation, a heuristic algorithm for moderately large networks is also proposed. Case studies are carried out to analyze the basic properties of the formulation and the performance of the proposed heuristic. With the proposed formulation, it is possible to identify the configurations that ensure minimum spectrum occupation with different kinds of protection for each lightpath. Different kinds of modulation formats are considered and contrasted to the benchmark case of a single modulation format and using the same kind of protection for all lightpaths

Marine Biodiversity in the Caribbean: Regional Estimates and Distribution Patterns

This paper provides an analysis of the distribution patterns of marine biodiversity and summarizes the major activities of the Census of Marine Life program in the Caribbean region. The coastal Caribbean region is a large marine ecosystem (LME) characterized by coral reefs, mangroves, and seagrasses, but including other environments, such as sandy beaches and rocky shores. These tropical ecosystems incorporate a high diversity of associated flora and fauna, and the nations that border the Caribbean collectively encompass a major global marine biodiversity hot spot. We analyze the state of knowledge of marine biodiversity based on the geographic distribution of georeferenced species records and regional taxonomic lists. A total of 12,046 marine species are reported in this paper for the Caribbean region. These include representatives from 31 animal phyla, two plant phyla, one group of Chromista, and three groups of Protoctista. Sampling effort has been greatest in shallow, nearshore waters, where there is relatively good coverage of species records; offshore and deep environments have been less studied. Additionally, we found that the currently accepted classification of marine ecoregions of the Caribbean did not apply for the benthic distributions of five relatively well known taxonomic groups. Coastal species richness tends to concentrate along the Antillean arc (Cuba to the southernmost Antilles) and the northern coast of South America (Venezuela – Colombia), while no pattern can be observed in the deep sea with the available data. Several factors make it impossible to determine the extent to which these distribution patterns accurately reflect the true situation for marine biodiversity in general: (1) highly localized concentrations of collecting effort and a lack of collecting in many areas and ecosystems, (2) high variability among collecting methods, (3) limited taxonomic expertise for many groups, and (4) differing levels of activity in the study of different taxa