Showing papers on "Optical Transport Network published in 2004"

Urban optical wireless communication networks: the main challenges and possible solutions

Abstract: Urban optical wireless communication (UOWC) is rapidly gaining popularity as an effective means of transferring data at high rates over short distances The UOWC terminal includes an optical transmitter and a receiver positioned, for example, on high-rise buildings separated by several hundred meters Light beams propagating through the atmosphere carry the information from the transmitter to the receiver UOWC boasts many advantages over its rivals Notably, UOWC facilitates rapidly deployable, lightweight, high-capacity communication without licensing fees and tariffs However, UOWC still faces many challenges, including how to improve communication performance in adverse weather conditions or during building sway We present and evaluate some of the exciting new research approaches that have been suggested to deal with these issues, including optimization of telescope gain, new technologies for pointing systems, and solutions at the network level

Optical burst switching: a new area in optical networking research

Abstract: In this tutorial, we give an introduction to optical burst switching and compare it with other existing optical switching paradigms. Basic burst assembly algorithms and their effect on assembled burst traffic characteristics are described first. Then a brief review of the early work on burst transmission is provided, followed by a description of a prevailing protocol for OBS networks called just-enough-time (JET). Algorithms used as an OBS core node for burst scheduling as well as contention resolution strategies are presented next. Trade-offs between their performance and implementation complexities are discussed. Recent work on QoS support, IP/WDM multicast, TCP performance in OBS networks, and labeled OBS is also described, and several open issues are mentioned.

Network Recovery: Protection and Restoration of Optical, SONET-SDH, IP, and MPLS

Abstract: Chapter 1: Introduction 1.1 Communications networks today 1.2 Network reliability 1.3 Different phases in a recovery process 1.4 Performance of recovery mechanisms: criteria 1.5 Classification of single-layer recovery mechanisms 1.6 Multi-layer recovery 1.7 Conclusion Chapter 2: SONET-SDH 2.1 Introduction: transmission networks 2.2 SDH and SONET Networks 2.3 Operational aspects 2.4 Ring protection 2.5 Linear Protection 2.6 Restoration 2.7 Case study 2.8 Summary 2.9 Recommended reference work and research-related topics Chapter 3: Optical Networks 3.1 Evolution of the optical network layer 3.2. The Optical Transport Network 3.3 Fault detection and propagation 3.4 Recovery in optical networks 3.5 Recovery mechanisms in ring-based optical networks 3.6 Recovery mechanisms in mesh-based optical networks 3.7 Ring-based versus mesh-based recovery schemes 3.8 Availability 3.9 Som recent trends in research 3.10 Summary Chapter 4: IP Routing 4.1 IP routing protocols 4.2 Analysis of the IP recovery cycle 4.3 Failure profile and fault detection 4.4 Dampening algorithms 4.5 FIS propagation (LSA origination and flooding) 4.6 Route computation 4.7 Temporary loops during network states changes 4.8 Load balancing 4.9 QOS guarantees during failure 4.10 Non Stop Forwarding: an example with OSPF 4.11 A case study with IS-IS 4.12 Summary 4.13 Algorithm complexity 4.14 Incremental SPF 4.15 Interaction between fast IGP convergence and NSF 4.16 Research related topics Chapter 5: MPLS Traffic Engineering 5.1 MPLS Traffic Engineering refresher 5.2. Analysis of the recovery cycle 5.3. MPLS Traffic Engineering global default restoration 5.4 MPLS Traffic engineering global path protection 5.5 MPLS Traffic Engineering local protection 5.6. Another MPLS Traffic Engineering recovery alternative 5.7. Load balancing 5.8 Comparison of global protection and local protection 5.9 Revertive versus non revertive modes 5.10 Failure profiles and fault detection 5.11 Case Studies 5.12 Standardization 5.13 Summary 5.14 RSVP signaling extensions for MPLS TE local protection 5.15 Backup path computation 5.16 Research related topics Chapter 6 Multi-Layer Networks 6.1 ASON / GMPLS networks 6.2 Generic multi-layer recovery approaches 6.3 Case studies 6.4 Conclusion 6.5 References

Ethernet PONs: a survey of dynamic bandwidth allocation (DBA) algorithms

Abstract: Optical networks are poised to dominate the access network space in coming years. Ethernet passive optical networks, which leverage the ubiquity of Ethernet at subscriber locations, seem destined for success in the optical access network. In this article we first provide a brief introduction to Ethernet passive optical networks, followed by a discussion of the problem of dynamic bandwidth allocation. We then introduce a framework for classifying dynamic bandwidth allocation schemes and provide a comprehensive survey of the dynamic bandwidth allocation methods proposed to date. We conclude with a side by side comparison of the schemes based on their most prominent characteristics, and outline future developments of dynamic bandwidth allocation schemes.

Method and apparatus for performing data flow ingress/egress admission control in a provider network

Abstract: A method, apparatus and network for transporting layer-2 frames, such as Ethernet MAC, ATM AAL5, and Frame Relay, over MPLS, SONET/SDH, or OTN optical transport networks as well as electrical transport networks is disclosed. The method establishes “pseudo-wires” between, for example, routers, Layer-2 packet switches, or SONET/SDH switches. Inter-related ingress and egress resource tables may be used by provider edge nodes to negotiate consistently managed data tunnels across a provider network on behalf of data flowing from/to a diverse base of customer edge nodes. Detailed network resource information particular to each of the data flows is exchanged between provider edge nodes during the creation of pseudo-wires. Admission control algorithms are applied at the ingress and egress points in order to manage the data flows into a provider network and exiting from a provider network to customer equipment. By applying pseudo-wire shuffling and preemption techniques, the providers can make better use of their network resources by admitting more pseudo-wires.

IP over Optical Networks: A Framework

Abstract: The Internet transport infrastructure is moving towards a model of high-speed routers interconnected by optical core networks. The architectural choices for the interaction between IP and optical network layers, specifically, the routing and signaling aspects, are maturing. At the same time, a consensus has emerged in the industry on utilizing IP-based protocols for the optical control plane. This document defines a framework for IP over Optical networks, considering both the IP-based control plane for optical networks as well as IP-optical network interactions (together referred to as "IP over optical networks").

Performance engineering of metropolitan area optical networks through impairment constraint routing

Abstract: We demonstrate the use of impairment constraint routing for performance engineering of transparent metropolitan area optical networks. Our results show the relationship between blocking probability and different network characteristics such as span length, amplifier noise figure, and bit rate, and provide information on the system specifications required to achieve acceptable network performance.

Method and apparatus for transporting packet data over an optical network

Abstract: A method, apparatus and network for transporting layer-2 frames, such as Ethernet MAC, ATM AAL5, and Frame Relay, over SONET, SDH, or OTN transport networks is disclosed. The method establishes “pseudo-wires” between, for example, SONET switches and directly on top of the SONET layer. The method may implement MPLS signaling protocols on traditional SONET switches for the purpose of aggregating layer-2 frames from the transport network edges, while the transport network itself is independent from IP and MPLS routing. This approach provides a number of advantages to the network carriers in terms of operation and equipment expense reduction. To enable the transport network to be independent from IP and MPLS, and avoid subsequent IP control message processing inside the networks, an edge-to-edge “tunneling” mechanism is designed to transmit control messages as a part of the SONET (or SDH or OTN) frame payload.

Optical communication network system

Abstract: A fiber optic communication system includes a device of switching and setting wavelength of optical signals used in communication by network-node equipments, which sets the mapping of the wavelength of the optical signal used in communication by the network node equipments, and the input/output ports of an array waveguide grating (AWG), so as to construct a predetermined logical network topology by a plurality of network node equipments which are connected via optical fibers to the array waveguide grating that outputs optical signals inputted to optical input ports, to predetermined optical output ports in accordance with the wavelength thereof. As well as enabling a simple construction, it is easy to realize flexible network design, construction, and operation, and different network groups can also be easily connected to each other. Moreover, a fiber optic communication system having robust security and which can be stably operated even at the time of failure is realized at low cost.

Ultrafast optoelectronic packet processing for asynchronous, optical-packet-switched networks [Invited]

Abstract: Feature Issue on Optical Interconnection Networks (OIN). We describe hybrid optical-electrical systems that perform header processing and buffering of ultrafast, asynchronous optical packets. Our systems are enabled by three key, novel devices: an all-optical serial-to-parallel converter, an optical clock-pulse generator, and a photonic parallel-to-serial-converter. These devices allow utilization of complementary metal-oxide semiconductor technology for compact, highly functional optical packet processing. A simplified node architecture for asynchronous, optical- packet-switched networks is made possible by these systems with all the necessary node functions integrated compactly. We also demonstrate an optical label swapper and a photonic random access memory for 40-Gbit/s, 16-bit, asynchronous optical packets.

Hamiltonian p-cycles for fiber-level protection in semi-homogeneous homogeneous and optical networks

Abstract: Recently there has been interest in DWDM-based optical networks that are assumed to employ exactly two working fibers uniformly on every span (or "link"). At the fiber level such networks are referred to as homogeneous networks. An interesting and highly efficient strategy for protection of such networks is to use a single dark-fiber p-cycle formed on a Hamiltonian cycle (if it exists). We show that in a homogeneous Hamiltonian network, a Hamiltonian p-cycle is the most efficient overall solution, although interestingly it does not always correspond to the individually most efficient p-cycle that can be formed. We also consider p-cycle planning in non-Hamiltonian but homogeneous networks and introduce the concept of a semi-homogenous network, specifically linked to the p-cycle concept. The proposed semi-homogeneous class of network actually realizes the theoretical lower bound on span-restorable networks in terms of network redundancy. Such networks also provide a strategy to accommodate certain patterns of capacity growth beyond a homogenous network without any increase in protection capacity. The work also demonstrates and explains why a single Hamiltonian p-cycle is not as efficient as a specifically optimized set of individual p-cycles in a "capacitated" (non-homogeneous) network where the working capacity on each span varies in a general way. These discussions provide new options for DWDM network architecture and also clarify some possible confusions about the applicability of Hamiltonian p-cycles and generalized sets of p-cycles.

Traffic engineering in next-generation optical Networks

Abstract: In this article traffic-engineering issues regarding network survivability, traffic grooming, impairment-aware routing, virtual-topology engineering, and coordination among multiple layers of network architecture will be reviewed for next-generation optical networks based on wavelength-division multiplexing (WDM). Due to the recent progress and development of WDM technology, increasing traffic demands can be readily accommodated in the next-generation optical networks. In spite of the huge amount of capacity (e.g., OC-192) provided by a WDM channel, enhanced network services and network performance improvement can only be achieved with efficient traffic-engineering mechanisms. The fault-tolerant function is essential in order to provide seamless services to users by protecting their traffic against failures in the optical network because many connections can be carried on a fiber. Because the capacity of a WDM channel is very large, its bandwidth may not be efficiently utilized by a single connection. Hence, low-rate user connections need to be efficiently aggregated through the traffic-grooming scheme. An intelligent routing algorithm is especially necessary in the optical network where signal impairments due to device imperfections might degrade the signal quality. In addition, the virtual network connectivity (topology) should be flexibly maintained such that dynamic changes to the traffic demands can be easily absorbed, which can be implemented by the virtual-topology engineering method in a WDM network. As the dominant usage of Internet protocol (IP) of the Internet is expected to reside directly above the WDM layer in the future network, the coordinated traffic-engineering scheme should be deliberately designed for the multi-layer network by judiciously choosing where to put many overlapping functions in the different network layers.

Policy-driven automated reconfiguration for performance management in WDM optical networks

Abstract: A key feature of optical networks based on WDM technology is the ability to optimize the configuration of optimal resources (i.e., wavelengths) with respect to a particular traffic demand. In the broadcast architecture, this involves the assignment of wavelengths to logical links, while in the optically switched architecture it additionally involves the routing of all-optical data paths known as lightpaths. This survey article is concerned with the problem of automatically updating the configuration of an optical network to accommodate changes in traffic demand, which entails making a reconfiguration policy decision, selecting a new configuration and migrating from the current to the new configuration. Existing solutions are classified according to their algorithmic properties, and compared on the basis performance, computational cost, and flexibility. Finally, open problems and research directions are discussed.

High-capacity multiservice optical label switching for the next-generation Internet

Abstract: This article presents an optical label switching technology geared toward the next-generation Internet, and highlights its promising potential to accommodate packet, burst, and circuit traffic in a unified optical layer. In particular, we provide detailed discussions on an architecture design for a high capacity optical label switching router by considering enabling optical technologies. In pursuit of an effective contention resolution scheme, we investigate an end-to-end solution by incorporating a traffic shaping function at the network edge with wavelength, time, and space dimensions contention resolution in the core network. Experimental results indicate that this scheme is capable of achieving very low packet loss rates. Furthermore, due to its natural compatibility with GMPLS architecture, optical label switching has great potential for a seamless upgrade of today's optical networks toward the next generation Internet.

Promising evolution paths for passive optical access networks

Abstract: Two evolution paths for power-splitting passive optical access networks are presented and discussed, where the focus is on both introduction of protection against fibre cuts and increase of bandwidth per customer. We show that fibre ring topology enables an easy introduction of protection to such tree-based systems. Wavelength division multiplexing (WDM) is assumed to be the key technology for bringing about more bandwidth to the customer in a later stage of network evolution, and first using coarse channel spacing. If an adequate demand for bandwidth as well as for protection is predictable it is useful to switch over to WDM fibre rings with optical add-drop multiplexing.

Self-adjusting optical add-drop multiplexer and optical networks using same

Abstract: A self-adjusting optical add-drop multiplexer monitors the power in a drop signal and attenuates the power in an add signal to match the power in express WDM channels (signals). When used in a fiber network, and more particularly, in a metro network, the deleterious effects of optical amplification are reduced. Power attenuation is also used in an optical switching assembly particularly useful in two-fiber ring network. The optical switching assembly monitors drop channels from the two rings of the network and attenuates the add channel(s) accordingly. An optical switch operates to direct the drop signal from one of the two rings to a receiver in accordance with a control signal based on the monitored drop channels. The self-adjusting optical add-drop multiplexer also monitors the power in the drop signals and issues an alarm if the drop signal is of a power level above or below predetermined levels.

Lightpaths on demand: a Web-services-based management system

Abstract: User-controlled optical networks play a key role in supporting electronic transfer of the enormous volumes of data generated in emerging e-science experiments. The ability of users to manage their own resources enables provisioning of bandwidth-guaranteed tunnels on demand without the costs associated with conventional managed services offered by network providers. However, building high-performance user-controlled networks has only become feasible in the last few years, as trends in the telecommunications industry have made it possible for users to purchase installed optical fiber and light it using their own premises equipment. Consequently, suitable network management technologies have not yet evolved. In particular, there is presently no means for users to easily provision bandwidth-guaranteed tunnels across multiple independent management domains. In this article we present a user-controlled lightpath management system that addresses this problem. We begin by reviewing the high-level functionality of the system. Then we examine the software architecture. Finally, we discuss design challenges faced while building the system and propose future extensions.

Optical network topology databases and optical network operations

Abstract: A number of wavelength division multiplexing (WDM) access nodes employ a distributed search based scheme to build network topology databases based on a set of connectivity constraints (1230). A set of one or more connectivity constraints that include quality or service (QoS) based criteria are applied on a physical network topology of a WDM optical network to divide that optical network into separate service levels (910) whose topologies (920) are determined for each of the service levels. A number of WDM access nodes of an optical network employ a source based scheme to establish communication paths (1145). Each of these access nodes stores a set of one or more network topology databases based on a set of connectivity constraints. Each of these nodes employs a messaging scheme to propagate notification of changes in the optical network to other nodes to maintain their databases.

Wavelength-division-multiplexed passive optical network

Abstract: A wavelength division multiplexing passive optical network including optical lines for link is disclosed. The passive optical network includes a plurality of optical network units each of which generates an upstream optical signal; a central office for generating downstream optical signals to be provided to each of the optical network units, and differentially converting each of the upstream optical signals into a monitoring signal and a received signal. Changes in the wavelength of each of the upstream optical signals are monitored and if there is an abnormality in each optical line by using relevant monitoring signals. The network also includes a remote node for multiplexing and outputting the upstream optical signals to the central office, and demultiplexing and outputting the downstream optical signals to corresponding optical network units.

SUCCESS-DWA: a highly scalable and cost-effective optical access network

Abstract: Passive optical networks have been identified as promising access solutions that can open the first-mile bottleneck, bringing gigabits-per-second data rates to end users. Current TDM PONs enjoy low cost by sharing resources in time, but suffer from limited capacity. In the future, WDM technology may be employed to achieve high performance. In this article we introduce a novel PON employing dynamic wavelength allocation to provide bandwidth sharing across multiple physical PONs. Tunable lasers, arrayed waveguide gratings, and coarse/fine filtering combine to create a flexible new optical access solution. The network's excellent scalability can bridge the gap between conventional TDM PONs and WDM PONs. The powerful architecture is a promising candidate for next-generation optical access networks.

Architecture for dynamic connectivity in an edge photonic network architecture

Abstract: A network arrangement for aggregation of groups of tunable sources in a photonic network is disclosed. The network arrangement includes transmit edge elements having a plurality of tunable optical transmitters, an optical switch and a cyclic optical multiplexer, and receive edge elements having optical demultiplexers, optical switches and a plurality of optical receivers. A variety of arrangements are disclosed including protected and unprotected network architectures. The network arrangement disclosed is particularly useful for overcoming the problem of scaling a photonic network.

Semiconductor optical amplifiers: performance and applications in optical packet switching (Invited)

Abstract: Semiconductor optical amplifiers (SOAs) are a versatile core technology and the basis for the implementation of a number of key functionalities central to the evolution of highly wavelength-agile all-optical networks. We present an overview of the state of the art of SOAs and summarize a range of applications such as power boosters, preamplifiers, optical linear (gain-clamped) amplifiers, optical gates, and modules based on the hybrid integration of SOAs to yield high-level functionalities such as all-optical wavelength converters/regenerators and small space switching matrices. Their use in a number of proposed optical packet switching situations is also highlighted.

Waveband routing and merging in hybrid optical networks

Abstract: Hybrid hierarchical optical cross-connects leverages the benefits of both all-optical (OOO) and optical-electrical (OEO) switching for a cost-effective solution in future optical networks. The design goal using hybrid cross-connects is to minimize the sum of two cost metrics: OEO switching cost and OOO switching cost. This paper proposes two different waveband merging architectures and minimum cost routing and merging algorithms for offline traffic scenario. The simulation based results show that the proposed algorithms provide higher cost benefit as compared to existing algorithms that do not rely on waveband merging architecture.

Broadband building blocks [optical networks]

Abstract: This article has focused on optical networks using WDM to provide broadband network solutions with increased functionality, capacity, and reach. The building blocks in this type of networks, i.e., OADMs and OXCs, have been discussed in detail. The different architectures and technology options used in these types of nodes have been investigated. A comparison between WS and BS OADM architectures has been given, while OXCs have been classified into opaque and transparent. The WS and B&S transparent OXC architectures have been discussed in detail, and the various technology options in terms of optical switching have been covered. The system performance of OADMs and OXCs including their cascadability has been analyzed in terms of OSNR, crosstalk, amplifier transients, and filter concatenation effects.

Single-fiber protection in telecommunications networks

Abstract: A solution for detecting and recovering from a failure in a protected single-fiber passive optical network. A detector is used to detect the degradation in power level of optical signals. Furthermore, the invention discloses a variable symmetric split ratio approach to improve the number of splits (e.g. the number of ONUs). A single-fiber passive optical network is disclosed that uses a plurality of passive nodes connected in the optical fiber between the interfaces, wherein in the passive nodes 2-by-2 splitters/combiners are used to couple optical power from and into the optical fiber at a predetermined split ratio.

Network control and management challenges in opaque networks utilizing transparent optical switches

Abstract: There is a potential for significant cost, footprint, and power savings by eliminating unnecessary opto-electronic conversions on a signal path in a core optical mesh network. The article addresses and clarifies some fundamental issues surrounding all-optical networking and all-optical switching, and analyzes the trade-offs between transparent and opaque networking. It investigates a number of networking and interface compatibility issues that arise for an opaque network with transparent switches, and presents a number of ways to address these issues.

Light trails: a sub-wavelength solution for optical networking

Abstract: All-optical networks are able to transport data from source to destination entirely in the optical domain. This is a departure from current optical networks that rely on optical-electrical-optical (OEO) conversion at each intermediate connection node to route data properly. The opacity inherent in traditional networks is costly in terms of limiting bandwidth and increasing switching complexity. MPLS, OBS and OPS have been proposed as solutions for realizing an all-optical network. MPLS and OBS have the advantages of creating all-optical connections between nodes, but do not allow intermediate nodes to use the wavelength as well. Additionally, optical switches are constantly being reconfigured to accommodate new connections. OPS can make switching decisions in the optical domain, but the technology is immature. Light trail technology tries to avoid the pitfalls of immature technology, the inability of intermediate nodes to use a connection wavelength, and the constant reconfiguration of switches. A light trail is a unidirectional optical bus between nodes that allows intermediate nodes to access the bus. The goal is to minimize the amount of active switching that needs to be done by allowing intermediate nodes to use a connection that has already been setup. Connections are not constantly being setup and torn down, but rather exist for as long as they are being used by any of the nodes along their light trail.

Optical label swapping in a packet-switched optical network using optical carrier suppression, separation, and wavelength conversion

Abstract: We have experimentally demonstrated for the first time how to realize label swapping in an optical network where the label and payload are generated using optical carrier suppression and separation. The bit-error-rate performance for both the payload and label are evaluated at different nodes in this optical network.

Field demonstration of in-line all-optical wavelength conversion in a WDM dispersion managed 40-Gbit/s link

Abstract: The development of wavelength-division multiplexing (WDM) all-optical transport networks is an interesting solution to increase the capacity of long-haul transmission systems and to solve the route-exhaust problems of metropolitan networks, driving down the cost of that traffic. Routing can be achieved using a transparent device able to select and interchange wavelengths, such as an all-optical wavelength converter. In this paper, an optical transport network over an embedded link located between Rome and Pomezia in Italy is emulated. The transmission has been realized along a WDM, 5/spl times/100 km long, dispersion managed link at 40 Gb/s. The in-line rerouting process has been controlled by means of an all-optical wavelength converter realized with a periodically poled lithium niobate waveguide. Moreover, a polarization-independent scheme for the converter has been exploited to allow the in-line signal processing. This scheme is based on the counterpropagation of TE and TM signal components along the same guide and results extremely compact. In this paper it is demonstrated that wavelength conversion and rerouting add no penalty with respect to the simple transmission along the embedded cable. This result seems to be another step toward the feasibility of true all-optical networks.

Hierarchical Routing with QoS Constraints in Optical Transport Networks

Abstract: Optical Transport Networks (OTN) with automatical switching capabilities are named ASON. Hierarchical routing is required in the ASON recommendations to achieve scalability. Basically, hierarchical routing consists of three main components, an aggregation scheme, an update policy and a routing algorithm. This paper proposes a new network structure focusing on these three components. We propose a new aggregation scheme; an update policy based on a threshold value; and we also extend an already proposed routing mechanism to be applied to a hierarchical network. Main skill of this routing mechanism is to reduce the connection blocking increase because of selecting paths based on inaccurate routing information. This inaccuracy is introduced both by the aggregation process and by the update policy.