Framework for waveband switching in multigranular optical networks: part I-multigranular cross-connect architectures

Optical networks using wavelength-division multiplexing (WDM) are the foremost solution to the ever-increasing traffic in the Internet backbone. Rapid advances in WDM technology will enable each fiber to carry hundreds or even a thousand wavelengths (using dense-WDM, or DWDM, and ultra-DWDM) of traffic. This, coupled with worldwide fiber deployment, will bring about a tremendous increase in the size of the optical cross-connects, i.e., the number of ports of the wavelength switching elements. Waveband switching (WBS), wherein wavelengths are grouped into bands and switched as a single entity, can reduce the cost and control complexity of switching nodes by minimizing the port count. This paper presents a detailed study on recent advances and open research issues in WBS networks. In this study, we investigate in detail the architecture for various WBS cross-connects and compare them in terms of the number of ports and complexity and also in terms of how flexible they are in adjusting to dynamic traffic. We outline various techniques for grouping wavelengths into bands for the purpose of WBS and show how traditional wavelength routing is different from waveband routing and why techniques developed for wavelength-routed networks (WRNs) cannot be simply applied to WBS networks. We also outline how traffic grooming of subwavelength traffic can be done in WBS networks. In part II of this study [Cao , submitted to J. Opt. Netw.], we study the effect of wavelength conversion on the performance of WBS networks with reconfigurable MG-OXCs. We present an algorithm for waveband grouping in wavelength-convertible networks and evaluate its performance. We also investigate issues related to survivability in WBS networks and show how waveband and wavelength conversion can be used to recover from failures in WBS networks

Multi-Granular Optical Cross-Connect: Design, Analysis, and Demonstration

A fundamental issue in all-optical switching is to offer efficient and cost-effective transport services for a wide range of bandwidth granularities. This paper presents multi-granular optical cross-connect (MG-OXC) architectures that combine slow (ms regime) and fast (ns regime) switch elements, in order to support optical circuit switching (OCS), optical burst switching (OBS), and even optical packet switching (OPS). The MG-OXC architectures are designed to provide a cost-effective approach, while offering the flexibility and reconfigurability to deal with dynamic requirements of different applications. All proposed MG-OXC designs are analyzed and compared in terms of dimensionality, flexibility/reconfigurability, and scalability. Furthermore, node level simulations are conducted to evaluate the performance of MG-OXCs under different traffic regimes. Finally, the feasibility of the proposed architectures is demonstrated on an application-aware, multi-bit-rate (10 and 40 Gbps), end-to-end OBS testbed

Resource Management in Survivable Multi-Granular Optical Networks

The last decade witnessed a wild growth of the Internet traffic, promoted by bandwidth-hungry applications such as Youtube, P2P, and VoIP. This explosive increase is expected to proceed with an annual rate of 34% in the near future, which leads to a huge challenge to the Internet infrastructure. One foremost solution to this problem is advancing the optical networking and switching, by which abundant bandwidth can be provided in an energy-efficient manner. For instance, with Wavelength Division Multiplexing (WDM) technology, each fiber can carry a mass of wavelengths with bandwidth up to 100 Gbits/s or higher. To keep up with the traffic explosion, however, simply scaling the number of fibers and/or wavelengths per fiber results in the scalability issue in WDM networks. One major motivation of this dissertation is to address this issue in WDM networks with the idea of waveband switching (WBS). This work includes the author\u27s study on multiple aspects of waveband switching: how to address dynamic user demand, how to accommodate static user demand, and how to achieve a survivable WBS network. When combined together, the proposed approaches form a framework that enables an efficient WBS-based Internet in the near future or the middle term. As a long-term solution for the Internet backbone, the Spectrum Sliced Elastic Optical Path (SLICE) Networks recently attract significant interests. SLICE aims to provide abundant bandwidth by managing the spectrum resources as orthogonal sub-carriers, a finer granular than wavelengths of WDM networks. Another important component of this dissertation is the author\u27s timely study on this new frontier: particulary, how to efficiency accommodate the user demand in SLICE networks. We refer to the overall study as the resource management in multi-granular optical networks. In WBS networks, the multi-granularity includes the fiber, waveband, and wavelength. While in SLICE networks, the traffic granularity refers to the fiber, and the variety of the demand size (in terms of number of sub-carriers)

Resilient optical multicasting utilizing cycles in WDM optical networks

High capacity telecommunications of today is possible only because of the presence of optical networks. At the heart of an optical network is an optical fiber whose data carrying capabilities are unparalleled. Multicasting is a form of communication in wavelength division multiplexed (WDM) networks that involves one source and multiple destinations. Light trees, which employ light splitting at various nodes, are used to deliver data to multiple destinations. A fiber cut has been estimated to occur, on an average, once every four days by TEN, a pan-European carrier network. This thesis presents algorithms to make multicast sessions survivable against component failures. We consider multiple link failures and node failures in this work. The two algorithms presented in this thesis use a hybrid approach which is a combination of proactive and reactive approaches to recover from failures. We introduce the novel concept of minimal-hop cycles to tolerate simultaneous multiple link failures in a multicast session. While the first algorithm deals only with multiple link failures, the second algorithm considers the case of node failure and a link failure. Two different versions of the first algorithm have been implemented to thoroughly understand its behavior. Both algorithms were studied through simulators on two different networks, the USA Longhaul network and the NSF network. The input multicast sessions to all our algorithms were generated from power efficient multicast algorithms that make sure the power in the receiving nodes are at acceptable levels. The parameters used to evaluate the performance of our algorithms include computation times, network usage and power efficiency. Two new parameters, namely, recovery times and recovery success probability, have been introduced in this work. To our knowledge, this work is the first to introduce the concept of minimal hop cycles to recover from simultaneous multiple link failures in a multicast session in optical networks

Impact of physical layer impairments on large ROADM architectures

Most of today’s optical networks, use reconfigurable optical add/drop multiplexers (ROADMs) as nodes. To become more dynamic and flexible, these nodes architectures evolved over the years. The colorless, directionless and contentionless functionalities are now standard, however, current architectures have poor scalability due to limitations on wavelength selective switches dimensions. Hence, due to constant increase in data traffic, current architectures might become a bottleneck to manufacture future large-scale ROADMs. In this work, the hardware cost and in-band crosstalk generation inside different large-scale ROADM architectures, is compared with conventional architectures. Moreover, an analysis of optical filtering, amplified spontaneous emission (ASE) noise and in-band crosstalk impact in the performance of an optical network, with nodes based on the most promising large-scale architecture, the interconnected A architecture, is performed. This performance is assessed through Monte-Carlo simulation with 16 point quadrature amplitude modulation with polarization-division multiplexing (PDM-16QAM) and PDM- 32QAM signals with 200 Gb/s and 250 Gb/s, respectively. Two architectures are considered for the interconnected A express structure, Broadcast and Select (B&S) and Route and Select (R&S). For the add/drop structure, a bank-based structure is considered. The maximum number of cascaded ROADMs, considering all the studied impairments, is 5 and 7 nodes for a 32 GBaud 16QAM signal, respectively, for B&S and R&S architectures. A 32QAM signal reaches 3 and 4 nodes, respectively, for B&S and R&S architectures. The main penalty in transmission is the ASE noise generated by optical amplifiers throughout the network, having the in-band crosstalk and optical filtering penalties a lower contribution.A maioria das redes óticas são atualmente compostas por multiplexadores óticos de inserção/extração reconfiguráveis (ROADMs, em inglês) nos nós, cuja arquitetura tem evoluído para se tornarem mais dinâmicos e flexíveis. As funcionalidades colorless, directionless e contentionless estão hoje normalizadas, no entanto, as arquiteturas atuais tornam-se pouco escaláveis para ROADMs de elevada dimensão, devido a limitações nos comutadores seletivos no comprimento-de-onda. Neste trabalho, a comparação entre os custos associados e a geração de crosstalk homódino em diferentes arquiteturas propostas para ROADMs de elevada dimensão e as arquitecturas tradicionais é efetuada. É também analisado o impacto da filtragem ótica, ruído de emissão espontânea amplificada (ASE, em inglês) e crosstalk homódino no desempenho de uma rede com nós baseados na arquitetura denominada "Interconnected A". A avaliação é feita através de simulação Monte-Carlo com sinais multiplexados por divisão na polarização e modulação de amplitude em quadratura, PDM-16QAM e PDM-32QAM a 200 Gb/s e 250 Gb/s, respetivamente. Foram consideradas duas configurações para os ROADMs estudados, Broadcast and Select e Route and Select (B&S e R&S, em inglês) e uma estrutura de inserção/extração denominada "bank-based". Quando considerados todos os efeitos, o alcance máximo da rede é de 4 e 7 nós para um sinal 16QAM, respetivamente, para configurações B&S e R&S. Para um sinal 32QAM, é de 3 e 4 nós, respetivamente, para configurações B&S e R&S. A principal penalidade na transmissão deve-se ao ruído ASE gerado nos amplificadores óticos ao longo da rede, tendo a penalidade devido ao crosstalk homódino e a filtragem ótica uma menor contribuição

On-Chip Optical Interconnection Networks for Multi/Manycore Architectures

The rapid development of multi/manycore technologies offers the opportunity for highly parallel architectures implemented on a single chip. While the first, low-parallelism multicore products have been based on simple interconnection structures (single bus, very simple crossbar), the emerging highly parallel architectures will require complex, limited-degree interconnection networks. This thesis studies this trend according to the general theory of interconnection structures for parallel machines, and investigates some solutions in terms of performance, cost, fault-tolerance, and run-time support to shared-memory and/or message passing programming mechanisms

Survivability stategies in all optical networks.

Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2006.Thesis (M.Sc.)-University of KwaZulu-Natal, 2006.Recent advances in fiber optics technology have enabled extremely high-speed transport of different forms of data, on multiple wavelengths of an optical fiber, using Dense Wavelength Division Multiplexing (DWDM). It has now become possible to deploy high-speed, multi-service networks using DWDM technology. As the amount of traffic carried has increased, any single failure can be catastrophic. Survivability becomes indispensable in such networks. Therefore, it is imperative to design networks that can quickly and efficiently recover from failures. Most research to date in survivable optical network design and operation focuses on single link failures, however, the occurrence of multiple-link failures are not uncommon in networks today. Multi-link failure scenarios can arise out of two common situations. First, an arbitrary link may fail in the network, and before that link can be repaired, another link fails, thus creating a multi-link failure sequence. Secondly, it might happen in practice that two distinct physical links may be routed via the same common duct or physical channel. A failure at that shared physical location creates a logical multiple-link failure. In this dissertation, we conduct an intensive study of mechanisms for achieving survivability in optical networks. From the many mechanisms presented in the literature the focus of this work was on protection as a mechanism of survivability. In particular four protection schemes were simulated and their results analyzed to ascertain which protection scheme achieves the best survivability in terms of number of wavelengths recovered for a specific failure scenario. A model network was chosen and the protection schemes were evaluated for both single and multiple link and node failures. As an indicator of the performance of these protection schemes over a period of time average service availability and average loss in traffic for each protection scheme was also simulated. Further simulations were conducted to observe the percentage link and node utilization of each scheme hence allowing us to determine the strain each protection scheme places on network resources when traffic in the network increases. Finally based on these simulation results, recommendations of which protection scheme and under what failure conditions they should be used are made.Recent advances in fiber optics technology have enabled extremely high-speed transpor

Investigation of performance issues affecting optical circuit and packet switched WDM networks

Optical switching represents the next step in the evolution of optical networks. This thesis describes work that was carried out to examine performance issues which can occur in two distinct varieties of optical switching networks. Slow optical switching in which lightpaths are requested, provisioned and torn down when no longer required is known as optical circuit switching (OCS). Services enabled by OCS include wavelength routing, dynamic bandwidth allocation and protection switching. With network elements such as reconfigurable optical add/drop multiplexers (ROADMs) and optical cross connects (OXCs) now being deployed along with the generalized multiprotocol label switching (GMPLS) control plane this represents the current state of the art in commercial networks. These networks often employ erbium doped fiber amplifiers (EDFAs) to boost the optical signal to noise ratio of the WDM channels and as channel configurations change, wavelength dependent gain variations in the EDFAs can lead to channel power divergence that can result in significant performance degradation. This issue is examined in detail using a reconfigurable wavelength division multiplexed (WDM) network testbed and results show the severe impact that channel reconfiguration can have on transmission performance. Following the slow switching work the focus shifts to one of the key enabling technologies for fast optical switching, namely the tunable laser. Tunable lasers which can switch on the nanosecond timescale will be required in the transmitters and wavelength converters of optical packet switching networks. The switching times and frequency drifts, both of commercially available lasers, and of novel devices are investigated and performance issues which can arise due to this frequency drift are examined. An optical packet switching transmitter based on a novel label switching technique and employing one of the fast tunable lasers is designed and employed in a dual channel WDM packet switching system. In depth performance evaluations of this labelling scheme and packet switching system show the detrimental impact that wavelength drift can have on such systems

Effective fiber bandwidth utilization in TDM WDM optical networks

Ph.DDOCTOR OF PHILOSOPH