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Arquitetura de nós e engenharia de tráfego em redes ópticas / Nodes architecture and traffic engineering in optical networksAlmeida Neto, Helvécio Moreira de 25 September 2009 (has links)
A interligação de várias redes de telecomunicação ampliou a cobertura, mas tornou a operabilidade entre elas complexa, principalmente por causa da arquitetura resultante, formada por várias camadas. Estas camadas lidam com protocolos e taxas de transmissão diferentes e com sinais elétricos e ópticos. Diante desse cenário, a alternativa usual de expandir os recursos proporcionalmente ao crescimento da demanda é inviável devido ao elevado custo. Assim, soluções eficientes que agregam os benefícios das tecnologias ópticas e eletrônicas na arquitetura de nós e no gerenciamento de tráfego tornaram-se uma necessidade importante no projeto, expansão e gerenciamento de redes de telecomunicação. Os nós que permitem a comutação de tráfego na camada óptica e eletrônica e a agregação de tráfego em várias granularidades têm sido empregados para fazer o melhor uso possível dos recursos disponíveis nas redes. Esses nós são conhecidos na literatura como MG-OXCs. Nessa pesquisa, foi proposta uma abordagem dos nós MG-OXCs de uma e três camadas com a inclusão de recursos como conversão de comprimento de onda e agregação de tráfego. Também foi proposto um método de cálculo do custo desses nós baseado no volume de utilização das portas. Posteriormente foram inseridos fatores de degradação do sinal óptico para a análise da camada física de redes com os nós MGOXCs. Adicionalmente, para o gerenciamento de tráfego, foi proposto um esquema de escolha de comprimentos de onda chamado de canal específico e um esquema de monitoramento baseado na intensidade de tráfego. A meta principal é a redução da probabilidade de bloqueio de solicitação de conexão. Em redes ópticas, os modelos de nós propostos conseguem diminuir o número de portas dos nós comutadores tradicionais além de realizar a comutação de tráfego de conexões de diferentes valores de largura de banda. O esquema do canal específico consegue melhorar a utilização da largura de banda dos comprimentos de onda e diminui a probabilidade de bloqueio e o esquema do monitoramento diminui o número de conexões bloqueadas devido ao aumento dos recursos. Resultados numéricos apresentados demonstram a potencialidade dos algoritmos propostos para gerenciar recursos e rotear o tráfego das redes de telecomunicação. / Integrating telecommunication networks has enlarged the coverage, but has made operations more complex, mainly because of the architecture, formed by various layers. These layers deal with different protocols and transmission rates, as well as electrical and optical signals. The usual alternative of expanding the resources proportionally to the demand is impractical due to the high cost. Therefore, efficient solutions which add to the benefits of optical and electronic technology in node architecture and traffic management are essential in the design, expansion and management of telecommunications networks. The nodes that enable traffic switching in the optical and electronic layer and traffic grooming have been used to make the best use of the available resources in the networks. These nodes are known as MG-OXCs. In this research, an approach based on MG-OXCs was proposed with one and three layers, which include the wavelength conversion and traffic grooming. Additionally, a method to calculate the node costs based on their use of ports was proposed. The work also considered optical signal impairments in order to analyze the network physical layer with MG-OXCs nodes. For the purpose of traffic management, a scheme which sets specific wavelengths for different bandwidths and a scheme which monitors the flow of traffic were proposed. The main aim is to reduce the blocking probability of connection requests. In optical networks, the node models proposed are able to reduce the number of ports used in usual optical cross connects and switch the traffic connections using different bandwidths. The scheme of setting specific wavelengths for different bandwidths improves the bandwidth use and the blocking probability. The scheme which monitors the flow of traffic achieves blocking probability reduction due to the increase in resources. The numerical results presented show the feasibility of the proposed algorithms to manage resources and switch traffic in telecommunication networks.
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Towards quantum telecommunication and a Thorium nuclear clockRadnaev, Alexander G. 17 August 2012 (has links)
This thesis presents the investigations of Rubidium atoms in magneto-optical traps and triply charged Thorium ions in electrodynamic traps for future advances in long-distance quantum telecommunication, next generation clocks, and fundamental tests of current physical theories. Experimental realizations of two core building blocks of a quantum repeater are described: a multiplexed quantum memory and a telecom interface for long-lived quantum memories. A color change of single-photon level light fields by several hundred nanometers in an optically thick cold gas is demonstrated, while preserving quantum entanglement with a remotely stored matter excitation. These are essential elements for long-distance quantum telecommunication, fundamental tests of quantum mechanics, and applications in secure communication and computation. The first trapping and laser cooling of Thorium-229 ions are described. Thorium-229 nuclear electric quadrupole moment is revealed by hyperfine spectroscopy of triply charged Thorium-229 ions. A system to search for the isomer nuclear transition in Thorium-229 is developed and tested with the excitation of a forbidden electronic transition at 717 nm. Direct excitation of the nuclear transition with laser light would allow for an extremely accurate clock and a sensitive test bed for variations of fundamental physical constants, including the fine structure constant.
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[en] CHARACTERISATION OF ALLOPTICAL WAVELENGTH CONVERSION BY CROSS-GAIN MODULATION IN SEMICONDUCTOR OPTICAL AMPLIFIERS / [pt] CARACTERIZAÇÃO DA CONVERSÃO DE COMPRIMENTO DE ONDA POR MODULAÇÃO DE GANHO CRUZADO EM AMPLIFICADORES ÓPTICOS SEMICONDUTORESRAFAEL DE OLIVEIRA RIBEIRO 21 March 2006 (has links)
[pt] A conversão de comprimento de onda de sinais por meio de
técnicas totalmente
ópticas é um assunto inovador e de extrema necessidade
para as redes com
roteamento de comprimento de onda; a técnica de conversão
de comprimentos
de onda por modulação de ganho cruzado é uma das mais
simples, em princípio,
que atinge este objetivo. Duas modalidades são
apresentadas neste trabalho:
a clássica, também conhecida por pump & probe, e uma nova,
a de modulação
de ganho cruzado do espectro da ASE em um SOA. A técnica
pump e
probe é apresentada, assim como um experimento baseado
nesta. A técnica de
modulação de ganho cruzado da ASE é explorada como
alternativa à técnicas
de conversão de comprimento de onda que necessitam de
outra fonte de luz,
para a qual o sinal deve ser convertido. Na modulação de
ganho cruzado da
ASE, o sinal é convertido de luz coerente para incoerente;
e, uma vez modulado
o espectro da ASE do SOA, este é filtrado no comprimento
de onda que se
deseja obter a conversão. Assim, este conversor pode ser
sintonizável, já que
não é um parâmetro de entrada que define o comprimento de
onda convertido,
e sim um filtro passa-faixa ao fim do dispositivo. Para se
avaliar os tempos
de resposta da técnica, a conversão é feita utilizando-se
pulsos elétricos ultracurtos
(50 ps), o que não havia sido feito até então. / [en] Wavelength conversion of optical signals by all-optical
techniques is an innovative
and necessary technology for wavelength routed networks in
the near
future; the cross-gain modulation method is one of the
simplest, in form, to attain
this goal. Two categories of the main technique are
presented: the classic,
also known as pump and probe, and a novel one, named cross-
gain modulation
of the ASE spectrum of a SOA. The cross-gain modulation of
the ASE
spectrum is explored here as an alternative to previous
all-optical wavelength
conversion techniques that require another light source,
to which the incoming
signal is to be converted; the signal is converted from
coherent to incoherent
light; and, once modulated throughout the SOA`s ASE
spectrum, the signal
is then filtered at the central wavelength it is desired
to be converted. Thus,
this particular wavelength converter can be tunable, in
the sense that it is
reconfigurable, since a band pass filter located at the
end of the device selects
what wavelength the signal will be converted to. In order
to assess the response
times of the technique, the conversion is made for ultra
short electrical pulses
(50 ps), a feature unknown until now.
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Arquitetura de nós e engenharia de tráfego em redes ópticas / Nodes architecture and traffic engineering in optical networksHelvécio Moreira de Almeida Neto 25 September 2009 (has links)
A interligação de várias redes de telecomunicação ampliou a cobertura, mas tornou a operabilidade entre elas complexa, principalmente por causa da arquitetura resultante, formada por várias camadas. Estas camadas lidam com protocolos e taxas de transmissão diferentes e com sinais elétricos e ópticos. Diante desse cenário, a alternativa usual de expandir os recursos proporcionalmente ao crescimento da demanda é inviável devido ao elevado custo. Assim, soluções eficientes que agregam os benefícios das tecnologias ópticas e eletrônicas na arquitetura de nós e no gerenciamento de tráfego tornaram-se uma necessidade importante no projeto, expansão e gerenciamento de redes de telecomunicação. Os nós que permitem a comutação de tráfego na camada óptica e eletrônica e a agregação de tráfego em várias granularidades têm sido empregados para fazer o melhor uso possível dos recursos disponíveis nas redes. Esses nós são conhecidos na literatura como MG-OXCs. Nessa pesquisa, foi proposta uma abordagem dos nós MG-OXCs de uma e três camadas com a inclusão de recursos como conversão de comprimento de onda e agregação de tráfego. Também foi proposto um método de cálculo do custo desses nós baseado no volume de utilização das portas. Posteriormente foram inseridos fatores de degradação do sinal óptico para a análise da camada física de redes com os nós MGOXCs. Adicionalmente, para o gerenciamento de tráfego, foi proposto um esquema de escolha de comprimentos de onda chamado de canal específico e um esquema de monitoramento baseado na intensidade de tráfego. A meta principal é a redução da probabilidade de bloqueio de solicitação de conexão. Em redes ópticas, os modelos de nós propostos conseguem diminuir o número de portas dos nós comutadores tradicionais além de realizar a comutação de tráfego de conexões de diferentes valores de largura de banda. O esquema do canal específico consegue melhorar a utilização da largura de banda dos comprimentos de onda e diminui a probabilidade de bloqueio e o esquema do monitoramento diminui o número de conexões bloqueadas devido ao aumento dos recursos. Resultados numéricos apresentados demonstram a potencialidade dos algoritmos propostos para gerenciar recursos e rotear o tráfego das redes de telecomunicação. / Integrating telecommunication networks has enlarged the coverage, but has made operations more complex, mainly because of the architecture, formed by various layers. These layers deal with different protocols and transmission rates, as well as electrical and optical signals. The usual alternative of expanding the resources proportionally to the demand is impractical due to the high cost. Therefore, efficient solutions which add to the benefits of optical and electronic technology in node architecture and traffic management are essential in the design, expansion and management of telecommunications networks. The nodes that enable traffic switching in the optical and electronic layer and traffic grooming have been used to make the best use of the available resources in the networks. These nodes are known as MG-OXCs. In this research, an approach based on MG-OXCs was proposed with one and three layers, which include the wavelength conversion and traffic grooming. Additionally, a method to calculate the node costs based on their use of ports was proposed. The work also considered optical signal impairments in order to analyze the network physical layer with MG-OXCs nodes. For the purpose of traffic management, a scheme which sets specific wavelengths for different bandwidths and a scheme which monitors the flow of traffic were proposed. The main aim is to reduce the blocking probability of connection requests. In optical networks, the node models proposed are able to reduce the number of ports used in usual optical cross connects and switch the traffic connections using different bandwidths. The scheme of setting specific wavelengths for different bandwidths improves the bandwidth use and the blocking probability. The scheme which monitors the flow of traffic achieves blocking probability reduction due to the increase in resources. The numerical results presented show the feasibility of the proposed algorithms to manage resources and switch traffic in telecommunication networks.
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Ανάπτυξη συστημάτων κωδίκων για την ανίχνευση και διόρθωση σφαλμάτων σε δεδομένα μετάδοσηςΤυχόπουλος, Αυξέντιος 16 June 2010 (has links)
Το ερευνητικό αντικείμενο της παρούσας διατριβής υπάγεται στον «Έλεγχο
Σφαλμάτων» (Error Control), έναν επιστημονικό χώρο με καθοριστικής σημασίας
συνεισφορά στην εξέλιξη των ψηφιακών τηλεπικοινωνιών. Πιο συγκεκριμένα, η
παρούσα διατριβή πραγματεύεται την εφαρμογή του «ελέγχου σφαλμάτων» στην
οπτική μετάδοση. Κατά τη διάρκεια της τελευταίας δεκαπενταετίας (‘93-‘08), τρεις
γενιές «άμεσης διόρθωσης σφαλμάτων» (FEC) έχουν διαδεχθεί η μία την άλλη, σε
ανταπόκριση προς τις ολοένα απαιτητικότερες προδιαγραφές των οπτικών ζεύξεων
(υψηλότεροι ρυθμοί μετάδοσης και πυκνότερα οπτικά πλέγματα).
Κατά κανόνα, οι μέθοδοι FEC κωδικοποιούν τα δεδομένα εισόδου χωρίς να
έχουν γνώση γι’ αυτά (π.χ. δομή, πρωτόκολλο) και χωρίς να επεμβαίνουν σ’ αυτά.
Η προσέγγιση αυτή καλείται «κωδικοποίηση εκτός ζώνης» (Out-Band Coding –
OBC) και συνεπάγεται αύξηση του ρυθμού μετάδοσης στο οπτικό κανάλι σε σχέση
με το ρυθμό των δεδομένων εισόδου, ανάλογα με το ποσοστό πλεονασμού του
κώδικα. Ωστόσο, ο τελικός ρυθμός μετάδοσης στο κανάλι μπορεί να διατηρηθεί
αμετάβλητος, αν το πρωτόκολλο μετάδοσης προβλέπει την ύπαρξη πλεονάσματος
και μέρος αυτού μπορεί να διατεθεί για κωδικοποίηση FEC. Η εναλλακτική αυτή
προσέγγιση καλείται «κωδικοποίηση εντός ζώνης» (In-Band Coding – IBC).
Η «σύγχρονη ψηφιακή ιεραρχία» (SDH) και το «σύγχρονο οπτικό δίκτυο»
(SONET) είναι τα πρότυπα, που σήμερα κυριαρχούν στις οπτικές τηλεπικοινωνίες.
Με αφθονία πλεονάσματος στα πλαίσια μετάδοσης, τα παραπάνω σύγχρονα δίκτυα
προσφέρονται για την IBC. Στα πλαίσια της παρούσας διατριβής, τα SDH & SONET
αναλύθηκαν από κοινού για την εύρεση της βέλτιστης μεθόδου IBC με βάση έναν
αριθμό από κριτήρια. Καταρχήν εξετάστηκε διεξοδικά το πλεόνασμα μετάδοσης για
να εντοπιστούν τα διαθέσιμα bytes και να αιτιολογηθεί η δέσμευσή τους για την
IBC. Στη συνέχεια, αναζητήθηκε ο βέλτιστος κώδικας FEC για τα δεδομένα πλαίσια
μετάδοσης και με το δεδομένο πλεόνασμα (για την αποθήκευση των bits ισοτιμίας
του κώδικα). Η βελτιστοποίηση κάλυψε όλους τους γραμμικούς και συστηματικούς
κώδικες ανά κατηγορίες – ο χωρισμός τους σε κατηγορίες έγινε με βάση τις εξής
βασικές ιδιότητες: α) την αλφάβητο: «δυαδικοί» έναντι «μη-δυαδικών», και β) τη
διορθωτική ικανότητα: κώδικες κατάλληλοι για «τυχαία» (μεμονωμένα) σφάλματα
έναντι κατάλληλων για «ομοβροντίες» (ριπές) σφαλμάτων.
iii
Από την παραπάνω διαδικασία βελτιστοποίησης προέκυψε μία μέθοδος IBC,
που βασίζεται στο συρρικνωμένο Reed-Solomon κώδικα RS(240,236,9). Πρόκειται
για μία εντελώς νέα μέθοδο και δικαιολογεί τη διάκρισή της ως βέλτιστη, έχοντας
σαφή πλεονεκτήματα έναντι των μεθόδων, που είχαν προταθεί στο παρελθόν. Στα
πλαίσια της παρούσας διατριβής, η παραπάνω βέλτιστη μέθοδος προτείνεται με το
όνομα «FOCUS» για την κωδικοποίηση IBC στα δίκτυα SDH/SONET. Με στόχο την
ακριβή πειραματική αξιολόγηση της προτεινόμενης μεθόδου FOCUS, υλοποιήθηκε
κατόπιν ένας αριθμός από πρωτότυπα συστήματα, χρησιμοποιώντας τις διαθέσιμες
μικροκυματικές κάρτες «10g-Tester». Αναλυτικότερα, η μοντελοποίηση έγινε στη
γλώσσα περιγραφής υλικού VHDL και η υλοποίηση με προγραμματιζόμενη λογική
(Xilinx® XC2V3000-4 FPGA). Τέλος, η πειραματική αξιολόγηση της προτεινόμενης
μεθόδου FOCUS πραγματοποιήθηκε σε δύο διαδοχικές φάσεις:
Στην πρώτη φάση, το σύστημα FOCUS αξιολογήθηκε ως μία «ανεξάρτητη»
μέθοδος κωδικοποίησης FEC (stand-alone IBC evaluation). Η αξιολόγηση έγινε με
ρυθμό μετάδοσης STM-64 σε κατάλληλα διαμορφωμένη, πειραματική οπτική ζεύξη
«από-σημείο σε-σημείο» (point-to-point optical link), συνολικού μήκους ~88 χμ.
Στην παραπάνω ζεύξη μετρήθηκαν οι επιδόσεις του FOCUS κατά την αντιστάθμιση
των κυριότερων ατελειών της οπτικής μετάδοσης: α) της χρωματικής διασποράς
(CD), β) της «παρασιτικής» ενίσχυσης του θορύβου από οπτικούς ενισχυτές (ASE)
και γ) της μη-γραμμικής συμπεριφοράς (WDM -NL).
Στη δεύτερη φάση, το σύστημα FOCUS αξιολογήθηκε ως μία «αναβάθμιση»
για οπτικές ζεύξεις, οι οποίες διαθέτουν ήδη κωδικοποίηση OBC (evaluation of IBC
and OBC in concatenation). Πιο συγκεκριμένα, το σύστημα FOCUS συνδέθηκε σε
σειρά (ως εξωτερικός κώδικας) με το κατά ITU-T G.975 (2000) πρότυπο σύστημα
κωδικοποίησης (OBC). Σε αυτή τη συνδεσμολογία, το σύστημα FOCUS αποτελεί τη
δικλείδα ασφαλείας, που επεμβαίνει όταν ο εσωτερικός αποκωδικοποιητής (G.975)
υπερχειλίζεται από τα σφάλματα του καναλιού. Η αξιολόγηση της υβριδικής αυτής
μεθόδου κωδικοποίησης έγινε με ρυθμό μετάδοσης 10.66 Gb/s (SDH STM-64 x
15/14) σε μία καθαρά οπτική διάταξη μετατροπής μήκους κύματος, που αποτελείται
από δύο οπτικούς ενισχυτές πυριτίου (SOA-based MZI). Ειδικότερα, μετρήθηκαν:
α) η μείωση της ευαισθησίας της οπτικής διάταξης στις (τυχαίες) μεταβολές φάσης
των δύο σημάτων εισόδου και β) η καθαρή συνεισφορά του συστήματος FOCUS,
όταν αυτό επεμβαίνει ως δικλείδα ασφαλείας. Το FOCUS συγκεντρώνει σημαντική
καινοτομία, τόσο στην επινόηση όσο και στην υλοποίηση. Όλα τα συμπεράσματα
της αξιολόγησης έχουν δημοσιευτεί σε έγκυρα διεθνή περιοδικά και συνέδρια. / This Ph.D. thesis falls into “Error Control”, a scientific field with key contribution to
the evolution of digital telecommunications. In specific, this thesis treats optical transmission
in terms of “Error Control”. Noteworthy is the fact that during the last fifteen years (‘93-‘08),
three generations of “Forward Error Correction” (FEC) methods for optical transmission have
succeeded one another, in response to the increasingly demanding optical link specifications
(higher transmission rates, denser wavelength mesh).
In general, FEC-methods assume no prior knowledge of the input data (e.g. structure,
protocol); in addition, input data are not modified at all (i.e. under normal channel conditions,
output-data will be identical to the input data). This approach is called “Out-Band Coding”
(OBC) and incurs an increase of the optical channel data-rate relatively to the input data-rate,
inversely proportional to the coding-rate. Notwithstanding, the rate of the optical-channel can
be kept unchanged, on condition that the transmission protocol provides “overhead” and part
of this “overhead” can be allocated for parity-information. This alternative approach is called
“In-Band Coding” (IBC).
The “Synchronous Digital Hierarchy” (SDH) and the “Synchronous Optical Network”
(SONET) are currently the dominant standards in optical communications. The abundance of
overhead in transmission-frames renders these synchronous networks suitable for IBC. In this
thesis, SDH and SONET were analyzed together to determine the optimum IBC method with
respect to a number of criteria. Firstly, SDH/SONET transmission-overhead was scrutinized
in order to identify available bytes and justify their commitment to implement IBC. Next, the
optimum FEC-code was sought, given the size of the transmission-frames and the availability
of overhead (to allocate the parity bits). Optimization spanned all linear and systematic codes.
The codes were divided in groups according to the following fundamental properties: a) the
underlying alphabet: “binary” versus “non-binary” codes, and b) the corrective power: codes,
appropriate for “random” (isolated) errors versus codes, appropriate for “burst-form” errors.
Optimization resulted in an IBC-method, which relies on the shortened Reed-Solomon
code RS(240,236,9). This IBC-method is completely novel and its optimality can be verified
by the clear advantages, it presents over methods that were proposed in the past. In this thesis,
the above IBC-method is given the name “FOCUS” and proposed for IBC in SDH/SONET
networks. In order to accurately measure the performance of the proposed method “FOCUS”,
a number of prototypes were implemented by making use of microwave cards, called “10gv
Tester”. More specifically, “FOCUS” was modelled in the “VHDL” hardware description
language and its prototypes were implemented by means of a Xilinx® “XC2V3000-4” FPGA.
The experimental evaluation of the proposed method was conducted in two successive
phases:
During the first phase, “FOCUS” was evaluated as an independent (stand-alone) FEC
method. This evaluation took place at an STM-64 transmission-rate in a suitable experimental
“point-to-point” optical link, whose length was ~88 km. In the above link, the performance of
“FOCUS” was measured, in compensating the principal impairments of optical transmission:
a) the chromatic dispersion (CD), b) the parasitic amplification of noise by optical amplifiers
(ASE), and c) the non-linear behavior (WDM-NL).
During the second phase, “FOCUS” was evaluated as an “upgrade” for optical links,
which have already been equipped with OBC (evaluation of IBC and OBC in concatenation).
Specifically, “FOCUS” was concatenated with the OBC-method, which has been proposed in
rec. G.975 (ITU-T, 2000) with “FOCUS” as the outer- and “G.975” as the inner-code. In this
arrangement, “FOCUS” plays the role of the “safety-valve”, which prevents the inner decoder
(G.975) from deteriorating the error-rate of the optical link, when it is overwhelmed by severe
channel-conditions. The evaluation of this hybrid coding-method took place at a transmissionrate
of 10.66 Gb/s (SDH STM-64 x 15/14) in a purely optical wavelength conversion device,
which consists of two silicon optical amplifiers (SOA-based MZI). In the above wavelengthconversion
device, the following measurements were obtained: a) the reduction of sensitivity
of the optical wavelength converter to the (random) phase-changes of the two input signals,
and b) the net contribution of “FOCUS”, when acting as a “safety valve”.
“FOCUS” has many innovative aspects, both in its conception and the implementation
of its prototypes. All conclusions of the above two-phased experimental evaluation have been
published in international journals and conferences.
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