Experimental demonstration of gridless spectrum and time optical switching

An experimental demonstration of gridless spectrum and time switching is presented. We propose and demonstrate a bit-rate and modulation-format independent optical cross-connect architecture, based on gridless spectrum selective switch, 20-ms 3D-MEMS and 10-ns PLZT optical switches, that supports arbitrary spectrum allocation and transparent time multiplexing. The architecture is implemented in a four-node field-fiber-linked testbed to transport continuous RZ and NRZ data channels at 12.5, 42.7 and 170.8 Gb/s, and selectively groom sub-wavelength RZ channels at 42.7 Gb/s. We also showed that the architecture is dynamic and can be reconfigured to meet the routing requirements of the network traffic. Results show error-free operation with an end-to-end power penalty between 0.8 dB and 5 dB for all continuous and sub-wavelength channels

A novel ingress node design for video streaming over optical burst switching networks

This paper introduces a novel ingress node design which takes advantage of video data partitioning in order to deliver enhanced video streaming quality when using H.264/AVC codec over optical burst switching networks. Ns2 simulations show that the proposed scheme delivers improved video traffic quality without affecting other traffic, such as best effort traffic. Although the extra network load is comparatively small, the average gain in video PSNR was 5 dB over existing burst cloning schemes, with a maximum end-to-end delay of 17 ms, and jitter of less than 0.35 ms

Field trial of a 15 Tb/s adaptive and gridless OXC supporting elastic 1000-fold all-optical bandwidth granularity

An adaptive gridless OXC is implemented using a 3D-MEMS optical backplane plus optical modules (sub-systems) that provide elastic spectrum and time switching functionality. The OXC adapts its architecture on demand to fulfill the switching requirements of incoming traffic. The system is implemented in a seven-node network linked by installed fiber and is shown to provide suitable architectures on demand for three scenarios with increasing traffic and switching complexity. In the most complex scenario, signals of mixed bit-rates and modulation formats are successfully switched with flexible per-channel allocation of spectrum, time and space, achieving over 1000-fold bandwidth granularity and 1.5 Tb/s throughput with good end-to-end performance

Report on the development of the national assessment method for the ecological status of natural lakes in Greece, using the Biological Quality Element “Macrophytes” (Hellenic Lake Macrophytes-HeLM assessment method)

This report discusses the development of the national ecological assessment method for Greek natural lakes, based on the Biological Quality Element (BQE) “macrophytes”. Due to lack of a common natural lake type within the Mediterranean Lake Geographical intercalibration Group, there has not been a Med GIG Intercalibration Exercise for macrophytes in natural lakes. As a result, there are neither proposed assessment methods with common boundaries within the Med GIG, nor proposed metrics for the assessment of lakes based on macrophytes. It is noted that at the Mediterranean Lake Phytoplankton GIG Intercalibration Report, Member States defined two common water body types (L-M5/7 and L-M8) for reservoirs but none for natural lakes. The operation of the Greek water monitoring network started in 2012, following the publication of a Joint Ministerial Decision in 2011. The development of the current assessment method, as described in this report, is based on the data from this national water monitoring network. In particular, 50 lake water bodies (including 26 reservoirs) have been included in the monitoring network, out of which 16 have been monitored for macrophytes during the 3-year period of 2013-2015. Eight of them are warm monomictic, deep natural lakes with mean depth >9m (GR-DNL), when the other eight are polymictic, shallow natural lakes with mean depth 3-9m (GR-SNL). In these 16 lakes, a total of 272 monitoring sites were established for sampling macrophytes, which resulted in an equal number of macrophytic sampling transects, the data of which have been added in the national dataset. Thirty six of these sites were revisited during the 3-year period, and a total of 308 measurements of maximum macrophytic colonization depth were made. On this national dataset, the most suitable lake macrophyte based assessment components proposed by WISER deliverables D3.2-1 (Kolada et al., 2009), D3.2-2 (Dudley et al., 2011) and D3.2-3 (Kolada et al., 2011) were tested, in various combinations, so as to reach a final form that can be used as a national assessment method for Greece. As already mentioned, this is the first effort to establish a national method, which may need additions and improvements in the future, as well as intercalibration exercises among Member States in the Mediterranean GIG

HeLM: a macrophyte-based method for monitoring and assessment of Greek lakes

Zervas, D., Tsiaoussi, V. & Tsiripidis, I. HeLM: a macrophyte-based method for monitoring and assessment of Greek lakes. Environ Monit Assess 190, 326 (2018). https://doi.org/10.1007/s10661-018-6708-

Assessing the Ecological Water Level: The Case of Four Mediterranean Lakes

Petriki, O., D. Zervas, Ch. Doulgeris, D. Bobori. 2020. Assessing the Ecological Water Level: The Case of Four Mediterranean Lakes. Water: 12, 2977. doi:10.3390/w12112977The ecological water regime in lake water bodies refers to the water levels that enable the fulfillment of the ecosystem’s multiple functions. Therefore, assessing the ecological water regime necessitates the consideration of hydrological, economic, social, and ecological factors. The present research is focused on the assessment of the ecological water level of four Mediterranean natural lake ecosystems, considering their morphological and biological features. Initially, suggestions on the ecological water regime of the studied lakes were made based on an analysis of the lakes’ morphometry. Further, the ecological and biological requirements of the present fish fauna and aquatic macrophytic vegetation were considered. For the latter, mapping was conducted by extensive sampling according to international standards, in order to assess macrophyte composition, abundance, and chorology, as well as species sensitivity to water level fluctuations. The above guided the proposals on the optimal water level regime that should be met by each lake regarding the macrophytic and fish communities’ sustainability, also taking into account the unique hydromorphological features of each lake. The di erences in the outcoming results revealed that hydromorphological and biological approaches should be combined for assessing lakes’ ecological water regime

Intelligent design of optical networks: which topology features help maximise throughput in the nonlinear regime?

The overarching goal in intelligent network design is to deliver capacity when and where it is needed. The key to this is to understand which network topology characteristics impact the achievable network throughput. This is explored through the use of a new generative network model, taking into account physical layer network characteristics

Grazing Animal Production Systems and Grazing Land Characteristics in a Semi-Arid Region of Greece

Rough grazing in Greece cover about 40% of the total land area, is publicly owned and managed extensively (Hadjigeorgiou et al., 2002). The Prefecture of Larisa is in the centre of Greece, and has 212,000 ha of rough grazing land, with a variable topography ranging from sea level up to 3,000 m a.s.l. This area is utilized by a total population of 135,000 LU (mainly sheep, goats and some suckler cows), which consumes annually an appreciable fraction of their total nutrient requirements from rough grazing

Making intelligent topology design choices: understanding structural and physical property performance implications in optical networks [Invited]

The key goal in optical network design is to introduce intelligence in the network and deliver capacity when and where it is needed. It is critical to understand the dependencies between network topology properties and the achievable network throughput. Real topology data of optical networks are scarce, and often large sets of synthetic graphs are used to evaluate their performance including proposed routing algorithms. These synthetic graphs are typically generated via the Erdos–Renyi (ER) and Barabasi–Albert (BA) models. Both models lead to distinct structural properties of the synthetic graphs, including degree and diameter distributions. In this paper, we show that these two commonly used approaches are not adequate for the modeling of real optical networks. The structural properties of optical core networks are strongly influenced by internodal distances. These, in turn, impact the signal-to-noise ratio, which is distance dependent. The analysis of optical network performance must, therefore, include spatial awareness to better reflect the graph properties of optical core network topologies. In this work, a new variant of the BA model, taking into account the internodal signal-to-noise ratio, is proposed. It is shown that this approach captures both the effects of graph structure and physical properties to generate better networks than traditional methods. The proposed model is compared to spatially agnostic approaches, in terms of the wavelength requirements and total information throughput, and highlights how intelligent choices can significantly increase network throughputs while saving fiber