Fiber-Optic Communications

Transparències de l'assignatura "Comunicacions Òptiques" del curs 4B d'enginyeria de telecomunicacions.2010/201

A universal specification for multicore fiber crosstalk

© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.In order to transition multi-core fiber (MCF) technologies from their research state to volume production, the key design specifications have to be broadly agreed upon, first and foremost an acceptable level of inter-core crosstalk per unit length. Against common belief, we show that MCF crosstalk requirements per unit length are fairly independent of transmission distance in the context of modern coherent optical communication systems. As a consequence, a single value for the tolerable inter-core crosstalk per unit length can be used to specify MCFs, valid from metropolitan (~100 km) to trans-pacific (~10 000 km) deployment scenarios. The notion of a universal inter-core crosstalk specification allows for application-independent MCF designs (including a distance-independent optimum core density) and will facilitate the standardization and volume manufacturing of MCF.Peer ReviewedPostprint (author's final draft

Evaluation of probabilistic constellation shaping performance in Flex Grid over multicore fiber dynamic optical backbone networks [Invited]

In this paper, we present a worst-case methodology for estimating the attainable spectral efficiency over end-to-end paths across a Flex Grid over multicore fiber (MCF) optical network. This methodology accounts for physical link noise, as well as for the signal-to-noise ratio in the Add module (SNR TX ) of spatial-division-multiplexing-enabled reconfigurable optical add and drop multiplexers (SDM-ROADMs), introducing a dominant noise contribution over that of their Bypass and Drop modules. The proposed methodology is subsequently used to quantify the benefits that probabilistic constellation shaping (PCS) can bring to Flex-Grid/MCF dynamic optical backbone networks, compared to using traditional polarization-multiplexed modulation formats. In a first step, insight is provided into the spectral efficiency attainable along the precomputed end-to-end paths in two reference backbone networks, either using PCS or traditional modulation formats. Moreover, in each one of these networks, two SNR TX values are identified: the SNR TX yielding the maximum average paths’ spectral efficiency, as well as an SNR TX that, although slightly degrading the average paths’ spectral efficiency (by 10%), would yet enable a cost-effective SDM-ROADM Add module implementation. Extensive simulations are conducted to analyze PCS offered load gains under 1% bandwidth blocking probability. Furthermore, the study lastly focuses on finding out whether lower fragmentation levels in Flex-Grid/MCF dynamic optical backbone networks can push PCS benefits even further.Funding: Agencia Estatal de Investigación (PID2020-118011GB-C21, PID2020-118011GB-C22, RED2018-102585-T).Peer ReviewedPostprint (author's final draft

BIOTIC AND ABIOTIC EVENTS IN A SHALLOW CARBONATE PLATFORM (UPPER CRETACEOUS, SOUTH PYRENEAN MARGIN)

Πραγματοποιήθηκε μία λεπτoμεpής ιζηματολογική και παλαιοντολογική μελέτη των αποθέσεων ανθρακικής πλατφόρμας της περιοχής Serres Marginals (νότιο περιθώριο της Λεκάνης των Πυρρηναίων) και αναγνωρίσθηκαν τρεις ακολουθίες ρηχών ανθρακικών αποθέσεων (Cl, C2 και C3). Εντός των αποθέσεων ρηχής πλατφόρμας περιγράφονται ενδιάμεσης ενέργειας υποπαλιρροιακές έως ενδοπαλιρροιακές φάσεις, αβαθείς άμμοι υψηλής ενέργειας καθώς και λιμνοθαλάσσια έως λιμναία περιβάλλοντα.A detailed sedimentological and paleontological study of the Late Santonian-Late Campanian carbonate platform deposits of the Serres Marginals area (South margin of the Pyrenean Basin) has been performed. Three depositional shallow carbonate sequences have been distinguished (CI, C2 and C3). Within the shallow platform sequences moderate energy subtidal to intertidal, high energy sand-shoal, protected lagoon and restricted lagoon to lacustrine fades have been identified

Cost-effective spatial super-channel allocation in Flex-Grid/MCF optical core networks

Space Division Multiplexing (SDM) is a key technology to cope with the bandwidth limitations of single mode fibers. Multi-Core Fibers (MCFs) are considered as a promising candidate technology to implement SDM, due to their low inter-core crosstalk (ICXT), experimentally proven in laboratory prototypes. Among the different channel allocation options making use of the newly enabled space dimension, the so-called spatial super-channel (Spa-SCh) is the most likely solution to be implemented, given the inherent cost reduction of the joint-switching operation (i.e., jointly switching a spectrum portion in all MCF cores at once). This work targets the cost-effective Spa-SCh allocation over MCF-enabled Flex-Grid optical core networks. To this goal, state-of-the-art 22-core MCFs are assumed, although the proposed solutions are applicable to any MCF type. In particular, we propose and evaluate a partial-core assignment as a cost-effective strategy to improve spectrum utilization and save Capital Expenditure (CapEx) costs by minimizing the number of optical transceivers used per Spa-SCh. Numerical results reveal that reductions up to 44% and 33% in the number of active transceivers in the network can be obtained in national- and continental-wide backbone networks, respectively, without affecting the network Grade-of-Service (GoS), measured in terms of Bandwidth Blocking Probability (BBP). To evaluate the impact of the ICXT, we also compare the performance of the MCF scenarios under study against equivalent Multi-Fiber (MF) ones. From the obtained results, ICXT in MCF scenarios requires the utilization of less efficient modulation formats, which reduces the admissible offered network load by up to 17% for a 1% BBP target. Furthermore, this lower spectral efficiency also demands an increase of the symbol rate per sub-channel up to a 26%, a key indicator of the modulator electronic complexity.Peer ReviewedPostprint (author's final draft

Random number generation by coherent detection of quantum phase noise

In 2010 Qi et al. [Opt. Lett. 35(3), 312 (2010)] demonstrated a random number generator based on the drift of the phase of a laser due to spontaneous emission, The out-of-the-lab implementation of this scheme presents two main drawbacks: it requires a long and highly unbalanced interferometer to generate a random phase with uniform probability distribution, or alternatively, a shorter and slightly unbalanced interferometer that notwithstanding requires active stabilization and does not generate a uniform probability distribution without randomness extraction. Here we demonstrate that making use of the random nature of the phase difference between two independent laser sources and two coherent detectors we can overcome these limitations. The two main advantages of the system demonstrated are: i) it generates a probability distribution of quantum origin which is intrinsically uniform and thus in principle needs no randomness extraction for obtaining a uniform distribution, and ii) the phase is measured with telecom equipment routinely used for high capacity coherent optical communications. The speed of random bit generation is determined by the photodetector bandwidth and the linewidth of the lasers. As a by-product of our method, we have obtained images of how phase noise develops with time in a laser. This provides a highly visual alternative way of measuring the coherence time of a laser.Peer ReviewedPostprint (published version

Results and achievements of the ALLIANCE Project: New network solutions for 5G and beyond

Leaving the current 4th generation of mobile communications behind, 5G will represent a disruptive paradigm shift integrating 5G Radio Access Networks (RANs), ultra-high-capacity access/metro/core optical networks, and intra-datacentre (DC) network and computational resources into a single converged 5G network infrastructure. The present paper overviews the main achievements obtained in the ALLIANCE project. This project ambitiously aims at architecting a converged 5G-enabled network infrastructure satisfying those needs to effectively realise the envisioned upcoming Digital Society. In particular, we present two networking solutions for 5G and beyond 5G (B5G), such as Software Defined Networking/Network Function Virtualisation (SDN/NFV) on top of an ultra-high-capacity spatially and spectrally flexible all-optical network infrastructure, and the clean-slate Recursive Inter-Network Architecture (RINA) over packet networks, including access, metro, core and DC segments. The common umbrella of all these solutions is the Knowledge-Defined Networking (KDN)-based orchestration layer which, by implementing Artificial Intelligence (AI) techniques, enables an optimal end-to-end service provisioning. Finally, the cross-layer manager of the ALLIANCE architecture includes two novel elements, namely the monitoring element providing network and user data in real time to the KDN, and the blockchain-based trust element in charge of exchanging reliable and confident information with external domains.This work has been partially funded by the Spanish Ministry of Economy and Competitiveness under contract FEDER TEC2017-90034-C2 (ALLIANCE project) and by the Generalitat de Catalunya under contract 2017SGR-1037 and 2017SGR-605.Peer ReviewedPostprint (published version

Developing general cultural awareness in a monocultural English as a foreign language context in a Mexican university: a wiki-based critical incident approach

© 2013 Association for Language Learning. This article explores what the ‘intercultural turn’ might mean in the case of teaching English to speakers of other languages (TESOL). The discussion is contextualised in what has been termed the ‘expanding circle’ of English and focuses on an English as a foreign language (EFL) class in a Mexican university, a context where the full implications of a shift from EFL to English as a lingua franca (ELF) have yet to be addressed. We consider how the intercultural turn might be understood in this Mexican context and then present the rationale for, and design of, a technology-based (wiki) extra-curricular pilot project which adopted less of an EFL/cultural and more of an ELF/intercultural approach. We evaluate the evidence from this small-scale project in terms of students\u27 developing general cultural awareness and suggest that this type of project, an example of the intercultural turn, might be more widely applicable in similar ‘expanding circle’ EFL contexts

In Vitro Studies Evaluating Leaching of Mercury from Mine Waste Calcine Using Simulated Human Body Fluids

In vitro bioaccessibility (IVBA) studies were carried out on samples of mercury (Hg) mine-waste calcine (roasted Hg ore) by leaching with simulated human body fluids. The objective was to estimate potential human exposure to Hg due to inhalation of airborne calcine particulates and hand-to-mouth ingestion of Hg-bearing calcines. Mine waste calcines collected from Hg mines at Almadén, Spain, and Terlingua, Texas, contain Hg sulfide, elemental Hg, and soluble Hg compounds, which constitute primary ore or compounds formed during Hg retorting. Elevated leachate Hg concentrations were found during calcine leaching using a simulated gastric fluid (as much as 6200 μg of Hg leached/g sample). Elevated Hg concentrations were also found in calcine leachates using a simulated lung fluid (as much as 9200 μg of Hg leached/g), serum-based fluid (as much as 1600 μg of Hg leached/g), and water of pH 5 (as much as 880 μg of Hg leached/g). The leaching capacity of Hg is controlled by calcine mineralogy; thus, calcines containing soluble Hg compounds contain higher leachate Hg concentrations. Results indicate that ingestion or inhalation of Hg mine-waste calcine may lead to increased Hg concentrations in the human body, especially through the ingestion pathway

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Background: Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. // Methods: We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung's disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. // Findings: We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung's disease) from 264 hospitals (89 in high-income countries, 166 in middle-income countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in low-income countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. // Interpretation: Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between low-income, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030