709 research outputs found
QKD in Standard Optical Telecommunications Networks
To perform Quantum Key Distribution, the mastering of the extremely weak
signals carried by the quantum channel is required. Transporting these signals
without disturbance is customarily done by isolating the quantum channel from
any noise sources using a dedicated physical channel. However, to really profit
from this technology, a full integration with conventional network technologies
would be highly desirable. Trying to use single photon signals with others that
carry an average power many orders of magnitude bigger while sharing as much
infrastructure with a conventional network as possible brings obvious problems.
The purpose of the present paper is to report our efforts in researching the
limits of the integration of QKD in modern optical networks scenarios. We have
built a full metropolitan area network testbed comprising a backbone and an
access network. The emphasis is put in using as much as possible the same
industrial grade technology that is actually used in already installed
networks, in order to understand the throughput, limits and cost of deploying
QKD in a real network
Optical Network Models and their Application to Software-Defined Network Management
Software-defined networking is finding its way into optical networks. Here,
it promises a simplification and unification of network management for optical
networks allowing automation of operational tasks despite the highly diverse
and vendor-specific commercial systems and the complexity and analog nature of
optical transmission. A fundamental component for software-defined optical
networking are common abstractions and interfaces. Currently, a number of
models for optical networks are available. They all claim to provide open and
vendor agnostic management of optical equipment. In this work, we survey and
compare the most important models and propose an intent interface for creating
virtual topologies that is integrated in the existing model ecosystem.Comment: Parts of the presented work has received funding from the European
Commission within the H2020 Research and Innovation Programme, under grant
agreeement n.645127, project ACIN
A survey on OFDM-based elastic core optical networking
Orthogonal frequency-division multiplexing (OFDM) is a modulation technology that has been widely adopted in many new and emerging broadband wireless and wireline communication systems. Due to its capability to transmit a high-speed data stream using multiple spectral-overlapped lower-speed subcarriers, OFDM technology offers superior advantages of high spectrum efficiency, robustness against inter-carrier and inter-symbol interference, adaptability to server channel conditions, etc. In recent years, there have been intensive studies on optical OFDM (O-OFDM) transmission technologies, and it is considered a promising technology for future ultra-high-speed optical transmission. Based on O-OFDM technology, a novel elastic optical network architecture with immense flexibility and scalability in spectrum allocation and data rate accommodation could be built to support diverse services and the rapid growth of Internet traffic in the future. In this paper, we present a comprehensive survey on OFDM-based elastic optical network technologies, including basic principles of OFDM, O-OFDM technologies, the architectures of OFDM-based elastic core optical networks, and related key enabling technologies. The main advantages and issues of OFDM-based elastic core optical networks that are under research are also discussed
Optical network planning for static applications
Traffic demands on optical transport networks continue to grow, both in numbers
and in size, at an incredible rate. Consequently, the efficient use of network resources has
never been as important as today. A possible solution to this problem is to plan, develop
and implement efficient algorithms for static and/or dynamic applications in order to
minimize the probability of blocking and/or minimizing the number of wavelengths.
Static Routing and Wavelength Assignment (RWA) algorithms use a given set of optical
path requests and are intended to provide a long-term plan for future traffic. Static RWA
algorithms are important for current and future WDM (Wavelength-Division
Multiplexing) networks, especially when there is no wavelength conversion, the network
is highly connected or the traffic load is moderate to high.
In this dissertation, we propose to develop an optical network planning tool capable
of choosing the best optical path and assigning as few wavelengths as possible. This tool
is structured in five phases: in the first phase, the network physical topology is defined
by the adjacency matrix or by the cost matrix and the logical topology is defined by the
traffic matrix; in a second phase, the Dijkstra algorithm is used to find the shortest path
for each connection; in the third phase, the traffic routing is accomplished considering
one traffic unit between the source and destination nodes; in the fourth phase, the paths
are ordered using various ordering strategies, such as Shortest Path First, Longest Path
First and Random Path Order; finally, in the fifth phase, the heuristic algorithms for
wavelength assignment, such as Graph Coloring, First-Fit and Most-Used are used. This
tool is first tested on small networks (e.g. ring and mesh topologies), and then applied to
real networks (e.g. COST 239, NSFNET and UBN topologies). We have concluded that
the number of wavelengths calculated for each network is almost independent of the
Wavelength Assignment (WA) heuristics, as well as the ordering strategy, when a full
mesh logical topology is considered.Os pedidos de tráfego nas redes de transporte ópticas continuam a crescer, tanto em
número como em tamanho, a um ritmo incrível. Consequentemente, a utilização eficiente
dos recursos das redes nunca foi tão importante como hoje. Uma solução possível para
este problema passa por planear, desenvolver e implementar algoritmos eficientes para
aplicações estáticas e/ou dinâmicas de modo a minimizar a probabilidade de bloqueio
e/ou minimizar o número de comprimentos de onda. Os algoritmos de encaminhamento
e de atribuição de comprimentos de onda (RWA) estáticos utilizam um determinado
conjunto de pedidos de caminhos ópticos e visam fornecer um plano de longo prazo para
tráfego futuro. Os algoritmos RWA estáticos são importantes para as redes em
multiplexagem por divisão de comprimento de onda (WDM) atuais e futuras,
especialmente quando não há conversão de comprimento de onda, a rede é altamente
ligada ou a carga de tráfego é de moderada a alta.
Nesta dissertação, propomos desenvolver uma ferramenta de planeamento de redes
ópticas capaz de escolher o melhor caminho óptico e atribuir o mínimo de comprimentos
ondas possíveis. Esta ferramenta está estruturada em cinco fases: numa primeira fase é
definida a topologia física de rede pela matriz das adjacências ou pela matriz de custo e a
topologia lógica é definida pela matriz de tráfego; numa segunda fase é utilizado o
algoritmo Dijkstra para encontrar o caminho mais curto para cada ligação; na terceira fase
o encaminhamento de tráfego é realizado considerando uma unidade de tráfego entre os
nós de origem e destino; na quarta fase os caminhos são ordenados tendo em conta as
várias estratégias de ordenação, tais como Shortest Path First, Longest Path First e
Random Path Order; finalmente, na quinta fase, os algoritmos heurísticos são utilizados
para atribuição de comprimentos de onda, como Graph Coloring, First-Fit e Most-Used.
Esta ferramenta é primeiramente testada em redes pequenas (por exemplo, topologias em
anel e em malha), e depois é aplicada a redes reais (por exemplo, redes COST 239,
NSFNET e UBN). Concluímos que o número de comprimentos de onda calculados para
cada rede é quase independente da heurística para atribuição dos cumprimentos de onda,
bem como da estratégia de ordenação dos caminhos, quando uma topologia lógica em
malha completa é considerada
Spectral Efficiency Optimization in Flexi-Grid Long-Haul Optical Systems
Flexible grid optical networks allow a better exploitation of fiber capacity,
by enabling a denser frequency allocation. A tighter channel spacing, however,
requires narrower filters, which increase linear intersymbol interference
(ISI), and may dramatically reduce system reach. Commercial coherent receivers
are based on symbol by symbol detectors, which are quite sensitive to ISI. In
this context, Nyquist spacing is considered as the ultimate limit to
wavelength-division multiplexing (WDM) packing.
In this paper, we show that by introducing a limited-complexity trellis
processing at the receiver, either the reach of Nyquist WDM flexi-grid networks
can be significantly extended, or a denser-than-Nyquist channel packing (i.e.,
a higher spectral efficiency (SE)) is possible at equal reach. By adopting
well-known information-theoretic techniques, we design a limited-complexity
trellis processing and quantify its SE gain in flexi-grid architectures where
wavelength selective switches over a frequency grid of 12.5GHz are employed.Comment: 7 pages, 9 figure
Energy‐efficient colourless photonic technologies for next‐generation DWDM metro and access networks
Within the scope of our EU FP7 C3PO project, we are developing novel, energy-efficient, colourless photonic technologies for low-cost, next-generation dense wavelength-division-multiplexed metro transport and access networks. The colourless transmitters use reflective arrayed photonic integrated circuits, particularly hybrid reflective electroabsorption modulators, and multi-wavelength laser sources, with custom power-efficient driver circuitry. A low-loss piezoelectric beam-steering optical matrix switch allows for dynamic wavelength reconfigurability. Simplifying the required optical and electronic hardware, as well as avoiding the need for expensive, thermally-stabilised tuneable lasers, will yield cost and energy savings for data switching applications in future metro, access, and datacentre interconnection networks. We report on recent advancement towards these low-power optical networks, providing the latest systems results achieved with key enabling hybrid photonic integrated devices and electronic driver/receiver arrays for our targeted applications
A Transponder Aggregator with Efficient Use of Filtering Function for Transponder Noise Suppression
Colorless, directionless, and contentionless reconfigurable optical add/drop
multiplexing (CDC-ROADM) provides highly flexible physical layer network
configuration. Such CDC-ROADM must operate in multiple wavelength bands which
are being increasingly implemented in optical transmission systems. The
operation in C+L bands requires switch devices used in CDC-ROADM to also be
capable of multiband operation. Recent studies on wavelength division
multiplexing (WDM) systems have pointed out the impact of amplified spontaneous
emission (ASE) noise generated by signals of different wavelengths, which
causes OSNR degradation. Therefore, it is desirable to filter out the ASE noise
from different transponders when multiplexing multiple wavelengths at the
transmitter side, especially in a system with non-wavelength selective
combiners such as directional couplers and multicast switches. The use of
transponder aggregators with filtering functions, such as the M x N wavelength
selective switch (WSS), is preferable for this filtering. However, the downside
of these devices is that it is difficult to provide economical multiband
support. Therefore, we propose an economical transponder aggregator
configuration by allowing a certain amount of ASE superposition and reducing
the number of filtering functions. In this paper, we fabricated a prototype of
the proposed transponder aggregator by combining silica-based planar lightwave
circuit technology and C+L band WSS, both commercially available, and verified
its feasibility through transmission experiments. The novel transponder
aggregator is a practical solution for a multiband CDC-ROADM system with
improved OSNR performance.Comment: 10 pages, 11 figures. Submitted to IEEE Journal of Lightwave
Technology for possible publicatio
Spatial Light Modulation as a Flexible Platform for Optical Systems
Spatial light modulation is a technology with a demonstrated wide range of applications, especially in optical systems. Among the various spatial light modulator (SLM) technologies, e.g., liquid crystal (LC), magneto-optic, deformable mirror, multiple quantum well, and acoustic-optic Bragg cells, the ones based on liquid crystal on silicon (LCoS) have been gaining importance and relevance in a plethora of optical contexts, namely, in telecom, metrology, optical storage, and microdisplays. Their implementation in telecom has enabled the development of high-capacity optical components in system functionalities as multiplexing/demultiplexing, switching and optical signal processing. This technology combines the unique light-modulating properties of LC with the high-performance silicon complementary metal oxide semiconductor properties. Different types of modulation, i.e., phase, amplitude or combination of the two, can be achieved. In this book chapter, we address the most relevant applications of phase-only LCoS SLM for optical telecom purposes and the employment of SLM technology in photonic integrated circuits (PICs) (e.g., field-programmable silicon photonic (SiP) circuits and integrated SLM application to create versatile reconfigurable elements). Furthermore, a new SLM-based flexible coupling platform with applications in spatial division multiplexing (SDM) systems (e.g., to efficiently excite different cores in MCF) and characterization/testing of photonic integrated processors will be described
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