Showing papers on "Optical Transport Network published in 2013"

Software-defined optical networks technology and infrastructure: Enabling software-defined optical network operations [invited]

Abstract: Software-defined networking (SDN) enables programmable SDN control and management functions at a number of layers, allowing applications to control network resources or information across different technology domains, e.g., Ethernet, wireless, and optical. Current cloud-based services are pushing networks to new boundaries by deploying cutting edge optical technologies to provide scalable and flexible services. SDN combined with the latest optical transport technologies, such as elastic optical networks, enables network operators and cloud service providers to customize their infrastructure dynamically to user/application requirements and therefore minimize the extra capital and operational costs required for hosting new services. In this paper a unified control plane architecture based on OpenFlow for optical SDN tailored to cloud services is introduced. Requirements for its implementation are discussed considering emerging optical transport technologies. Implementations of the architecture are proposed and demonstrated across heterogeneous state-of-the-art optical, packet, and IT resource integrated cloud infrastructure. Finally, its performance is evaluated using cloud use cases and its results are discussed.

Extending software defined network principles to include optical transport

Abstract: Software defined networks are based on the principle of a centralized control plane separated from the network forwarding or switching plane that it controls. The switching plane can be heterogeneous, composed of network elements from multiple vendors, and it can provide distinct services with different characteristics, configurations, and control at the packet and/or optical layers. Abstracting the control plane from the network elements allows network-platform- specific characteristics and differences that do not affect services to be hidden. In addition, software defined networking (SDN) is based on the principle that applications can request needed resources from the network via interfaces to the control plane. Through these interfaces, applications can dynamically request network resources or network information that may span disparate technologies. For instance, the application layer can dynamically request and obtain network resources at the packet flow, circuit, or even optical level based on application layer requirements. Current SDN implementations focus on Ethernet switching primarily for data center resource optimization. This article reviews the benefits and challenges of extending SDN concepts to various transport network architectures that include optical wavelength and fiber switches, circuit switches, and sub-wavelength optical burst switches. Control plane implementations for optical networks are more complex since they must account for physical constraints including optical signal reachability, bandwidth availability and granularity, light path routing, and light path reconfiguration speed. The longterm goal is to apply SDN concepts across multi-layer multivendor networks in order to support a unified control structure.

Optical interconnection networks in data centers: recent trends and future challenges

Abstract: Warehouse-scale data center operators need much-higher-bandwidth intra-data center networks (DCNs) to sustain the increase of network traffic due to cloud computing and other emerging web applications. Current DCNs based on commodity switches require excessive amounts of power to face this traffic increase. Optical intra-DCN interconnection networks have recently emerged as a promising solution that can provide higher throughput while consuming less power. This article provides an update on recent developments in the field of ultra-highcapacity optical interconnects for intra-DCN communication. Several recently proposed architectures and technologies are examined and compared, while future trends and research challenges are outlined.

Software defined optical networks technology and infrastructure: Enabling software-defined optical network operations

Abstract: A control plane architecture based on OpenFlow for optical SDN is introduced. Requirements for its implementation are discussed considering emerging optical transport technologies. Two implementations of the architecture and results on their performance are reported.

Spatial multiplexing: The next frontier in network capacity scaling

Abstract: We outline a smooth evolution path of optical networks to spatial multiplexing by complementing deployed fiber infrastructure and existing WDM components with new integrated technologies.

Rate-adaptable optics for next generation long-haul transport networks

Abstract: We discuss the emerging rate-adaptable optical transmission technology and how this new technology may be employed to further reduce the transport network cost to meet ever growing bandwidth demand in the core network Two different types of transponders are considered: those adjusting either the transported bit rate (ie, client data rate) or the symbol rate (with a fixed bit rate) We propose a methodology for calculating the (normalized) cost to build out an entire long-haul transport network with several options for bit-rate-adaptable transponders By using link-length demands from an exemplary distance-diverse network, we demonstrate that time-domain hybrid-QAM-enabled fine-grain rate-adaptable transponders can reduce network cost by more than 20 percent within a traditional, fixed-bandwidth, wavelength-division-multiplexed grid We also argue that the total transponder expense using symbol-rate-adaptable technology will be greater than when using bit-rate-adaptable technology, as well as requiring more costly flex-grid ROADMs for channel routing

Radio-Over-Fiber Access Architecture for Integrated Broadband Wireless Services

Abstract: This paper introduces two radio-over-fiber (RoF) architectures for the future broadband optical-wireless access network-all-band RoF and band-mapped 60-GHz RoF that can be integrated in ultra-dense wavelength division multiplexing passive optical network (UDWDM-PON). Legacy wireless services and multi-gigabit millimeter-wave (mm-wave) applications are integrated and delivered simultaneously under one shared infrastructure. With centralized system control and signal processing, the proposed systems provide cost-effective and protocol-transparent solutions for the next-generation multi-service bundle in heterogeneous networks (HetNets). In the all-band RoF network where wireless services are kept at their original carrier frequencies, Wi-Fi, WiMAX, and 60-GHz high-speed mm-wave services are transmitted based on subcarrier multiplexing (SCM) and dual-wavelength heterodyne beating techniques in avoidance of optical filters and large-bandwidth optoelectronic components. In the indoor environment, the band-mapped mm-wave RoF design is illustrated with real-time analog television signal, Wi-Fi, and high-speed digital baseband data-all of which are transmitted over unified optical and air links. By mapping various wireless signals into 60-GHz sub-bands, the novel architecture achieves higher spectral efficiency and lower power consumption.

Technologies and protocols for data center and cloud networking

Abstract: Data center and cloud architectures continue to evolve to address the needs of large-scale multi-tenant data centers and clouds. These needs are centered around seven dimensions: scalability in computing, storage, and bandwidth, scalability in network services, efficiency in resource utilization, agility in service creation, cost efficiency, service reliability, and security. This article focuses on the first five dimensions as they pertain to networking. Large data centers are targeting support for tens of thousands of servers, exabytes of storage, terabits per second of traffic, and tens of thousands of tenants. In a data center, server and storage resources are interconnected with packet switches and routers that provide for the bandwidth and multi-tenant virtual networking needs. Data centers are interconnected across the wide area network via routing and transport technologies to provide a pool of resources, known as the cloud. High-speed optical interfaces and dense wavelength-division multiplexing optical transport are used to provide for high-capacity transport intra- and inter-datacenter. This article reviews various switching, routing, and optical transport technologies, and their applicability in addressing the networking needs of large-scale multi-tenant data centers.

New devices enabling software-defined optical networks

Abstract: Next-generation ROADM networks are incorporating an extensive range of new features and capabilities including colorless, directionless, and contentionless multiplexing and demultiplexing, flexible spectrum channel definition, and higher-order modulation formats. To efficiently support these new features, both new ROADM node architectures along with complementary optical components and technologies are being synergistically designed. In this article, we describe these new architectures, components, and technologies, and how they work together to support these features in a compact and costefficient manner.

Power Saving Techniques and Mechanisms for Optical Access Networks Systems

Abstract: This tutorial paper provides an overview of studies and works to address the power saving issue in the optical access network (OAN), which typically comprises passive optical networks (PONs) and Ethernet aggregators (EAs). First, it describes techniques to reduce the power consumption of the optical network unit in each subscriber's home. It outlines methods standardized in ITU-T such as “dozing” and “cyclic sleep,” as well as elucidating other techniques. Next, power saving at the optical line terminal (OLT)/EA side is focused. The energy-aware operation of link aggregation and its application to OAN are described to decrease power consumed by the EAs used with time-division multiaccess (TDMA) PONs. Finally, a selective OLT sleep technique is introduced for the next-generation wavelength division multiplexing (WDM)-TDMA PON with wavelength routing technologies.

The prospect of inter-data-center optical networks

Abstract: Mega data centers and their interconnection networks have drawn great attention in recent years because of the rapid public adoption of cloud-based services. The unprecedented amount of data that needs to be communicated between data centers imposes new requirements and challenges to inter-data-center optical networks. In this article, we discuss the traffic growth trends and capacity demands of Google?s inter-data-center network, and how they drive the network architectures and technologies to scale capacities and operational ease on existing fiber plants. We extensively review recent research findings and emerging technologies, such as digital coherent detection and the flexgrid dense wavelength-division multiplexed channel plan, and propose practical implementations, such as C+L-band transmission, packet and optical layer integration, and a software-defined networking enabled network architecture for both capacity and operational scaling. In addition, we point out a few critical areas that require more attention and research to improve efficiency and flexibility of an inter-data-center optical network: optical regeneration, data rate mismatch between Ethernet and optical transport, and real-time optical performance monitoring.

Five-Port Optical Router Based on Microring Switches for Photonic Networks-on-Chip

Abstract: We demonstrate a five-port optical router that is suitable for large-scale photonic networks-on-chip. The optical router is designed to passively route the optical signal travelling in one direction and actively route the optical signal making a turn. In the case that an XY dimension-order routing is used, the passive routing feature guarantees that the maximum power consumption to route the data through the network is a constant that is independent of the network size. The fabricated device has an efficient footprint of ~ 460 × 1000 μm2. The routing functionality of the device is verified by using a 12.5-Gbit/s optical signal. The capability of multiwavlength routing for the optical router is also explored and discussed.

960 Gb/s Optical Backplane Ecosystem Using Embedded Polymer Waveguides and Demonstration in a 12G SAS Storage Array

Abstract: An optical backplane ecosystem is described and demonstrated that is capable of multi-Tb/s bandwidth and is based on embedded polymer waveguides, passive optical backplane connectors, and midboard optical transceivers with bandwidth up to 28 Gb/s per lane. These systems provide the highest bandwidth-density, lowest power consumption, while maintaining the signal integrity. Ecosystems built around this architecture will provide the bandwidth-density required for next generation fabric interconnect for storage, switching, and routing applications in future high capacity generations of Data Centers and HPC systems. To demonstrate the applicability of this technology, it was used to provide embedded optical connectivity within a functional data storage enclosure.

WDM FSO network with turbulence-accentuated interchannel crosstalk

Abstract: A wavelength division multiplexing (WDM) access network using high-speed free-space optical (FSO) communication for the distribution link is proposed. Combining FSO communication with optical fiber can reduce the system cost and provide high-bandwidth access in regions where optical fiber installation is problematic. The WDM channels suffer from interchannel crosstalk, while the FSO communication performance in a clear atmosphere is limited by atmospherically induced scintillation. These impairments, plus the amplified spontaneous emission noise from optical amplification, combine in a potentially problematic way, particularly in the upstream direction, which is investigated here. This turbulence-accentuated crosstalk effect is considered for the cases of 1) signal turbulent but crosstalk not and 2) crosstalk turbulent but signal not. Error floors are obtained in each case. The FSO link length that can be supported in the general case of the hybrid network is investigated.

Framework system of grade software defined network software controller and implementation method thereof

Abstract: The invention discloses a framework system of a grade software defined network software controller and an implementation method thereof. The framework system and the implementation method are applied in a multi-domain optical transport network (OTN); an inter-domain mapping relation of a whole network view and a physical device network is established according to whole network topologic information by a primary (SDNOTN) controller; an inter-domain mapping processing request of the whole network view and the physical device network in each domain is sent to each auxiliary SDNOTN; and the domain mapping relation of the whole network view and the physical device network is established by the auxiliary SDNOTN controllers. Grade structures of the primary SDNOTN controller and the auxiliary SDNOTN controllers are arranged in the framework system, so that the mapping relation of the multi-domain whole network view and the overall physical device network in real sense is realized, and a whole network resource optimizing algorithm is realized in the real sense, so that the problem that the inter-domain link resource conflict occurs in a cross-domain service connection signaling process can be thoroughly solved.

Virtual topology mapping in elastic optical networks

Abstract: Virtualization improves the efficiency of networks by allowing multiple virtual networks to share a single physical network's resources. Next-generation optical transport networks are expected to support virtualization by accommodating multiple virtual networks with different topologies and bit rate requirements. Meanwhile, Optical Orthogonal Frequency-Division Multiplexing (OOFDM) is emerging as a viable technique for efficiently using the optical fiber's bandwidth in an elastic manner. OOFDM partitions the fiber's bandwidth into hundreds or even thousands of OFDM subcarriers that may be allocated to services. In this paper, we consider an OOFDM-based optical network and formulate a virtual network mapping problem for both static and dynamic traffic. This problem has several natural applications, such as e-Science, Grid, and cloud computing. The objective for static traffic is to maximize the subcarrier utilization, while minimizing the blocking ratio is the aim for dynamic traffic. Two heuristics are proposed and compared. Simulation results are presented to demonstrate the effectiveness of the proposed approaches.

On routing and spectrum allocation in spectrum-sliced optical networks

Abstract: The orthogonal frequency division multiplexing (OFDM) technology provides an opportunity for efficient resource utilization in optical networks. It allows allocation of multiple sub-carriers to meet traffic demands of varying size. Utilizing OFDM technology, a spectrum efficient and scalable optical transport network called SLICE was proposed recently. The SLICE architecture enables sub-wavelength, super-wavelength resource allocation and multiple rate data traffic that results in efficient use of spectrum. However, the benefit is accompanied by additional complexities in resource allocation. In SLICE architecture, in order to minimize the utilized spectrum, one has to solve the routing and spectrum allocation problem (RSA). In this paper, we focus our attention to RSA and (i) prove that RSA is NP-complete even when the optical network topology is as simple as a chain or a ring, (ii) provide approximation algorithms for RSA when the network topology is a binary tree or a ring, (iii) provide a heuristic for the network with arbitrary topology and measure the effectiveness of the heuristic with extensive simulation. Simulation results demonstrate that our heuristic significantly outperforms several other heuristics proposed recently for RSA.

DSP-based optical access approaches for enhancing NG-PON2 systems

Abstract: Motivated by recent progress in next-generation PON2, or NG-PON2, standardization, this article reviews digital signal processing technologies to further enhance NG-PON2 systems by realizing flexible and cost-effective optical access network deployments. First, flexible speed upgrades by DSP-enabled advanced modulation and multiplexing approaches are described, followed by a consideration of cost-performance trade-offs. Next, reach extension using DSP-based digital coherent reception and impairment compensation is overviewed. Finally, as a future goal, access network virtualization with reconfigurable optical line terminals and optical network units is discussed.

Virtualization in optical networks from network level to hardware level [invited]

Abstract: Elastic optical networking is attracting much attention as a promising solution to achieve spectrum-efficient transport of higher data rates at 100 Gbits/s and beyond. If we draw an analogy to virtualization in cloud computing, it can be seen as network level resource virtualization of optical networks where spectrum resources in optical links are segmented as shareable resources and adaptively aggregated to create a wide variety of optical channels (OChs). In this paper, we discuss the benefits of introducing virtualization into the optical domain from the viewpoints of the network level and the hardware level. In elastic optical networks, a frequency slot through which an OCh is transported and the OCh itself are explicitly decoupled. While the adaptability in the frequency slot is brought about by bandwidth variable wavelength-selective switches, the adaptability in an OCh is yielded by digital coherent technology that is employed in transponders and regenerators. It is emphasized that in order to achieve transponders and regenerators that accommodate heterogeneous traffic demands in an economical manner, simply being adaptive is not enough, and being shareable is essential. We refer to this concept as hardware level virtualization. As examples, we describe a multiflow transponder and an elastic regenerator with results that show proof of concept. Based on the hardware virtualization concept, we propose an elastic optical transport system (EOTS) architecture that enables cost- and energy-efficient IP traffic offloading to the optical domain and improves programmability and automation of optical networks.

Elastic optical networks: The global evolution to software configurable optical networks

Abstract: Worldwide operator deployment of high-speed 100G coherent optical networks is currently underway. To ensure a competitive solution offering significant performance improvements to cope with the ever-increasing traffic demand, a novel network concept has been proposed for improved resource utilization based on “elasticity”; specifically, the ability to make a number of previously fixed transmission parameters tunable, for example optical data rate or channel spacing. The benefits are numerous, including increased network capacity, lower cost per bit, and improved energy efficiency and scalability. In this paper, we review the work carried out within the Cooperation for a Sustained European Leadership in Telecommunications (CELTIC) Elastic-Optical NETwork (EO-Net) project towards advancing the state of software-configurable optical networking. We identify the key building blocks for enabling elastic optical networks to provide desired performance improvements over static optical networks. We examine the design of elastic transponders capable of data rate adaptation, interfaces between client packet devices and transponders supporting flexible traffic aggregation, and associated algorithms for traffic grooming and routing. We also perform network cost/energy analyses. Finally, we review the experimental demonstration of such elastic functionalities.

Dynamic transparent virtual network embedding over elastic optical infrastructures

Abstract: We propose a novel dynamic transparent virtual network embedding (VNE) algorithm, which considers node mapping and link mapping jointly, for network virtualization over optical orthogonal frequency-division multiplexing (O-OFDM) based elastic optical infrastructures. For each virtual optical network (VON) request, the algorithm first transfers the substrate optical network into a layered-auxiliary-graph according to the spectrum usage of each fiber link, then applies a node mapping approach that considers the local information of all substrate nodes, and accomplishes the link mapping, in a single layer of the auxiliary graph. The simulation results verify that the proposed algorithm considers the uniqueness of O-OFDM networks and outperforms two reference algorithms that directly apply the VNE schemes developed for Layer 2/3 or WDM network virtualization, by providing lower VON blocking probability. The simulations with a realistic topology also demonstrate that the average lengths of embedded substrate paths are well-controlled within the typical transmission reaches of O-OFDM signals. To the best of our knowledge, this is the first proposal that includes both link mapping and node mapping to address dynamic transparent VNE over elastic optical infrastructures.

Cost, power consumption and performance evaluation of metro networks

Abstract: We provide models for evaluating the performance, cost and power consumption of different architectures suitable for a metropolitan area network (MAN). We then apply these models to compare today's synchronous optical network/synchronous digital hierarchy metro rings with different alternatives envisaged for next-generation MAN: an Ethernet carrier grade ring, an optical hub-based architecture and an optical time-slotted wavelength division multiplexing (WDM) ring. Our results indicate that the optical architectures are likely to decrease power consumption by up to 75% when compared with present day MANs. Moreover, by allowing the capacity of each wavelength to be dynamically shared among all nodes, a transparent slotted WDM yields throughput performance that is practically equivalent to that of today's electronic architectures, for equal capacity.

Open transport switch: a software defined networking architecture for transport networks

Abstract: There have been a lot of proposals to unify the control and management of packet and circuit networks but none have been deployed widely. In this paper, we propose a simple programmable architecture that abstracts a core transport node into a programmable virtual switch, that meshes well with the software-defined network paradigm while leveraging the OpenFlow protocol for control. A demonstration use-case of an OpenFlow-enabled optical virtual switch implementation managing a small optical transport network for big-data applications is described. With appropriate extensions to OpenFlow, we discuss how the programmability and flexibility SDN brings to packet-optical backbone networks will be substantial in solving some of the complex multi-vendor, multi-layer, multi-domain issues service providers face today.

Forward error correction in optical core and optical access networks

Abstract: Forward error correction (FEC) techniques are essential for optical core and optical access networks In optical core networks, the emphasis is on high coding gains and extremely low output bit error rates, while allowing decoder realizations to operate at a throughput of 100 Gb/s and above Optical access networks operate at 10 Gb/s or above and require low-complexity FEC codes with low power consumption Coherent optical transmission with higher order modulation formats will become mandatory to achieve the high spectral efficiencies required in next-generation core networks In this paper, we provide an overview of these requirements and techniques, and highlight how coding and modulation can be best combined in optical core networks We also present guidelines for modulation and low-complexity FEC system design for optical access networks

Optical ring metro networks with flexible Grid and distance-adaptive optical coherent transceivers

Abstract: The utilization of distance-adaptive coherent optical transceivers in combination with a flexible finer-grained Wavelength Division Multiplexing (WDM) grid has been proposed in optical core networks to enable higher spectral efficiency and flexibility in the allocation of traffic flows. However, the application of distance-adaptive transceivers in metro networks, which are typically based on ring topologies and characterized by shorter distances and lower traffic volumes, is still an open research area both in terms of network resource savings and coherent technology requirements. This paper discusses and analyzes an optical metro ring network architecture with distance-adaptive coherent transceivers and formalizes the routing, modulation level, and spectrum assignment (RMLSA) optimization problem over such a network in order to evaluate the possible benefits introduced by the use of coherent technologies and of a spectrum grid of finer granularity in metro scenarios. Comparisons with legacy WDM systems show significant savings in terms of spectrum occupation and transceiver utilization.

Design of WDM RoF PON based on OFDM and optical heterodyne

Abstract: In this paper, we propose a WDM radio-over-fiber (RoF) passive optical network (PON) based on orthogonal frequency-division multiplexing (OFDM) and optical heterodyne. With OFDM and coherent receiving technology, the system achieves high, elastic bandwidth allocation and excellent transporting property. Using optical heterodyne, the network implements the wireless access without adding a radio source. We evaluate the performance of the system in terms of bit error rate, coverage area, and receiving eye diagram and obtain the network as an excellent wire/wireless access property.

Bursting Data between Data Centers: Case for Transport SDN

Abstract: Public and Private Enterprise clouds are changing the nature of WAN data center interconnects. Data center WAN interconnects today are pre-allocated, static optical trunks of high capacity. These optical pipes carry aggregated packet traffic originating from within the data centers while routing decisions are made by devices at the data center edges. In this paper, we propose a software-defined networking enabled optical transport architecture (Transport SDN) that meshes seamlessly with the deployment of SDN within the Data Centers. The proposed programmable architecture abstracts a core transport node into a programmable virtual switch that leverages the OpenFlow protocol for control. A demonstration use-case of an OpenFlow-enabled optical virtual switch managing a small optical transport network for a big-data application is described. With appropriate extensions to OpenFlow, we discuss how the programmability and flexibility SDN brings to packet-optical data center interconnect will be substantial in solving some of the complex multi-vendor, multi-layer, multi-domain issues that hybrid cloud providers face.

Demonstration of EDFA cognitive gain control via GMPLS for mixed modulation formats in heterogeneous optical networks

Abstract: We demonstrate cognitive gain control for EDFA operation in real-time GMPLS controlled heterogeneous optical testbed with 10G/100G/200G/400G lightpaths. Cognitive control maintains the network BER below FEC-limit for up to 6 dB of induced attenuation penalty.

Centralized PON Monitoring Scheme Based on Optical Coding

Abstract: We propose a centralized optical monitoring scheme in a passive optical network based on the 2-D optical frequency hopping/periodic coding scheme with the network recognition algorithm that converts the decoding operation into an electronic field. The analytical model for multiple-customers interference probability (MCIP) is developed and investigated. The results show that the small correlation distance and the low MCIP are achieved. Finally, we validate the feasibility of the scheme.

Benefits and requirements of flexible-grid ROADMs and networks [invited]

Abstract: Due to claims of enhanced spectral efficiency and the ability to accommodate future modulation formats, flexible-grid networks in which the center wavelength and passband width of the optical channels can be set on the fly have attracted wide attention. A flexible-grid reconfigurable optical add/drop multiplexer (ROADM) requires more than a flexible-grid wavelength-selective switch, and a flexible-grid network requires far more than flexible-grid ROADMs. We discuss the technologies required to enable flexible-grid networks. We examine the potential benefits of using flexible-grid ROADMs and compare this approach with alternative strategies.