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Showing papers on "Optical Transport Network published in 2003"


Journal ArticleDOI
TL;DR: This article summarizes in a systematic way the main OBS design parameters and the solutions that have been proposed in the open literature and shows how the framework achieves high traffic throughput and high resource utilization.
Abstract: Optical burst switching is a promising solution for all-optical WDM networks. It combines the benefits of optical packet switching and wavelength routing while taking into account the limitations of the current all-optical technology. In OBS, the user data is collected at the edge of the network, sorted based on a destination address, and grouped into variable sized bursts. Prior to transmitting a burst, a control packet is created and immediately sent toward the destination in order to set up a bufferless optical path for its corresponding burst. After an offset delay time, the data burst itself is transmitted without waiting for a positive acknowledgment from the destination node. The OBS framework has been widely studied in the past few years because it achieves high traffic throughput and high resource utilization. However, despite the OBS trademarks such as dynamic connection setup or strong separation between data and control, there are many differences in the published OBS architectures. In this article we summarize in a systematic way the main OBS design parameters and the solutions that have been proposed in the open literature.

242 citations


Journal ArticleDOI
TL;DR: The underlying principles and essential components for a practical optical multicast service are examined and a set of key research challenges are presented along with a survey of the literature.
Abstract: Optical layer multicast refers to the support of point-to-multipoint connections directly at the physical layer by employing passive devices capable of splitting the power of an input signal among several outputs. Optical multicast technology enables a broad set of applications and opens new directions to network design. We examine the underlying principles and essential components for a practical optical multicast service. We also present a set of key research challenges along with a survey of the literature.

223 citations


Journal ArticleDOI
TL;DR: The architecture implications of the invention of a radical technology building block that can have profound transforming effects on space system architectures and data network user applications are explored.
Abstract: With high-speed space optical crosslink being a reality, the construction of an optical satellite network as part of a larger integrated space-terrestrial network is now feasible. This paper explores the architecture implications of the invention of such a radical technology building block. Not only can the satellite network performance and cost undergo quantum-leap improvements but also such a network can have profound transforming effects on space system architectures and data network user applications.

187 citations


Proceedings ArticleDOI
09 Jul 2003
TL;DR: It is demonstrated that near ideal statistical multiplexing performance can be achieved using even quite inexpensive, blocking OTSI designs, suggesting that optical technology may one day be able to provide a cost-effective alternative to electronics in packet switching systems.
Abstract: Time Sliced Optical Burst Switching is a proposed variant of optical burst switching, in which switching is done in the time domain, rather than the wavelength domain. This eliminates the need for wavelength converters, the largest single cost component of systems that switch in the wavelength domain. We examine some of the key design issues for routers that implement time sliced optical packet switching. In particular, we focus on the design of the Optical Time Slot Interchangers (OTSIs) needed to effect the required time domain switching. We introduce a novel nonblocking OTSI design and also show how blocking OTSIs can be used to implement the required switching operations. We study the performance of systems using blocking OTSIs and demonstrate that near ideal statistical multiplexing performance can be achieved using even quite inexpensive, blocking OTSI designs. These results suggest that optical technology may one day be able to provide a cost-effective alternative to electronics in packet switching systems.

147 citations


Journal ArticleDOI
TL;DR: A novel network architecture for wavelength-division-multiplexed passive optical networks which can provide bidirectional 1:1 protection against any fiber cut between the remote node and the optical network units (ONUs).
Abstract: We propose a novel network architecture for wavelength-division-multiplexed passive optical networks which can provide bidirectional 1:1 protection against any fiber cut between the remote node and the optical network units (ONUs). In case of such fiber cut, the affected ONU can still communicate with the optical line terminal by rerouting the wavelength channels via the adjacent ONU.

118 citations


Book
01 Jul 2003
TL;DR: Optical Network Control is the first expert guide and single-source reference for controlling and managing optical networks as discussed by the authors, which fills the gap between optical network engineering and routing/signaling, helping both optical and IP professionals build networks that are more robust, flexible, manageable, and profitable.
Abstract: Optical Network Control is the first expert guide and single-source reference for controlling and managing optical networks. This book fills the gap between optical network engineering and routing/signaling-helping both optical and IP professionals build networks that are more robust, flexible, manageable, and profitable. Coverage includes: Designing networks to deliver a range of on-demand services from mission-critical, time-sensitive protected services to low-cost unprotected services Network control and operations in WDM/DWDM and SONET/SDH environments Control principles and features for evolving mesh-based optical networks and existing ring networks-with practical examples Emerging, proposed, and future optical routing/signaling protocols and standards including GMPLS, ASON and Optical UNI Optical network control planes: design, scenarios, interworking, and interactions with existing network management systems Crucial IETF, ITU-T, OIF, ANSI, Bellcore, and industry information-brought together for the first time

116 citations


Journal ArticleDOI
TL;DR: A new optics-based transport architecture that emulates fast switching in the network core via emerging fast tunable lasers at the network edge, and bypasses the need for fast optical switching and buffering is presented.
Abstract: We present a new optics-based transport architecture that emulates fast switching in the network core via emerging fast tunable lasers at the network edge, and bypasses the need for fast optical switching and buffering. The new architecture is capable of handling both asynchronous and synchronous traffic, for dealing with various bandwidth granularities and responding to dynamic changes in end-to-end traffic demands. The architecture also reduces the amount of layering in the transport network by eliminating packet and TDM switching, keeps the network core light (lightweight and transparent), and pushes intelligence to the network edge. We discuss technical challenges that arise in the new architecture and describe possible approaches to address them.

115 citations


Journal ArticleDOI
TL;DR: It is shown that contrary to common wisdom, IP over OTN can lead to substantial reduction in capital expenditure through reduction of expensive transit IP router ports, and the savings increases rapidly with the number of nodes in the network and traffic demand between nodes.
Abstract: With the advent of WDM technology, IP backbone carriers are now connecting core routers directly over point-to-point WDM links (IP over WDM). The advances and standardization in optical control plane technologies like GMPLS have substantially increased the intelligence of the optical layer and shown promise toward making dynamic provisioning and restoration of optical layer circuits a basic capability to be leveraged by upper network layers. In light of this, an architecture where a reconfigurable optical backbone (IP over OTN) consisting of SONET/SDH crossconnects/switches interconnected via DWDM links provides connectivity among IP routers is an emerging alternative. As carriers evolve their networks to meet the continued growth of data traffic in the Internet, they have to make a fundamental choice between the above architectural alternatives. In the current business environment, this decision is likely to be guided by network cost and scalability concerns. A reconfigurable optical backbone provides a flexible transport infrastructure that eases many operational hurdles, such as fast provisioning, robust restoration, and disaster recovery. It can also be shared with other service networks such as ATM, frame relay, and SONET/SDH. From that perspective, an agile transport infrastructure is definitely the architecture of choice. The IP-over-OTN solution is also more scalable since the core of the network in this architecture is based on more scalable optical switches rather than IP routers. But what about cost? Since the IP-over-OTN solution introduces a new network element, the optical switch, is it more expensive? We address that question by comparing IP-over-WDM and IP-over-OTN architectures from an economic standpoint using real-life network data. We show that contrary to common wisdom, IP over OTN can lead to substantial reduction in capital expenditure through reduction of expensive transit IP router ports. The savings increases rapidly with the number of nodes in the network and traffic demand between nodes. The economies of scale for the IP-over-OTN backbone increase substantially when we move traffic restoration from the IP layer to the optical layer. We also compare the two architectures from the perspective of scalability, flexibility, and robustness. Our observations make a strong case in favor of a switched optical backbone for building scalable IP networks.

114 citations


Proceedings ArticleDOI
11 May 2003
TL;DR: An existing work is extended to provide approximate and accurate models for the data loss analysis of single OBS node with and without wavelength conversion capability, and the accuracy of these models is evaluated by simulation results.
Abstract: As the optical network evolves from static long haul connection provider to an adaptive and "smart" backbone solution, optical burst switching (OBS) becomes an attractive scheme for its flexibility and efficiency. However, how to reduce data loss is a crucial issue in such an asynchronous and one-way reservation system. In this paper, we study one contention resolution strategy in OBS networks: deflection routing. We extend an existing work to provide approximate and accurate models for the data loss analysis of single OBS node with and without wavelength conversion capability. The accuracy of our models is evaluated by simulation results.

107 citations


Journal ArticleDOI
TL;DR: This work proposes an integrated routing strategy that takes into account constraints and dynamic occupancy of both the IP and optical layers in the routing process, which leads to optimization of network performance.
Abstract: Future transport networks will have to cope with the continuous growth of IP traffic. Furthermore, transport networks need to evolve so as to drastically reduce both deployment costs and operating expenses. A reasonable strategy to achieve this goal consists of simplifying the network architecture by reducing the number of layers. Assuming a peer model IP over optical network, we propose an integrated routing strategy that takes into account constraints and dynamic occupancy of both the IP and optical layers. The collaboration of both layers in the routing process leads to optimization of network performance. The main emphasis is on the implementation requirements of this grooming functionality using GMPLS-TE mechanisms. Simulation results show the benefits obtained by applying this strategy.

101 citations


Book
01 Jan 2003
TL;DR: This chapter discusses the construction of the WDM Network Puzzle, the Behavior of Light, and manufacturing issues in the optical communication systems.
Abstract: Chapter 1: Basic Concepts of Communications SystemsChapter 2: Optical Communication Systems OverviewChapter 3: The Behavior of LightChapter 4: Optical FibersChapter 5: Optical Fiber CablesChapter 6: Light Sources and TransmittersChapter 7: Photoiodes and ReceiversChapter 8: Connectors and SplicesChapter 9: Passive Optical ComponentsChapter 10: Active Optical ComponentsChapter 11: Optical AmplifiersChapter 12: Wavelength Division MultiplexingChapter 13: Constructing the WDM Network PuzzleChapter 14: Performance MeasuresChapter 15: Performance ImpairmentsChapter 16: Optical Link DesignChapter 17: Optical NetworksChapter 18: Network ManagementChapter 19: Test and MeasurementChapter 20: Manufacturing IssuesAPPENDIX A: UNITS, PHYSICAL CONSTANTS, AND CONVERSION FACTORSAPPENDIX B: ITU-T FREQUENCY AND WAVELENGTH GRIDAPPENDIX C: ACRONYMSINDEX

Proceedings ArticleDOI
09 Jul 2003
TL;DR: A general model is formed of this waveband hierarchy for a single optical node by analyzing two issues: the proper selection of waveband sizes and the assignment of wavebands for a limited set of input-output patterns of traffic.
Abstract: Aggregation of individual wavelengths into wavebands for their subsequent switching and routing as a single group is an attractive way for scalable and cost-efficient optical networks. We analyze the implications of this waveband hierarchy for a single optical node by analyzing two issues: the proper selection of waveband sizes and the assignment of wavebands for a limited set of input-output patterns of traffic. We formulate a general model and propose optimal algorithmic solutions for both problems. The performance of resulting sets of nonuniform wavebands is studied for several representative cases (a single node, an optical ring network, an optical mesh network). The results demonstrate improved optical throughput and reduced cost of switching and routing when using nonuniform waveband hierarchy.

Journal ArticleDOI
TL;DR: A WDM-based access network that directly connects end users over a wide area to the center node and provides guaranteed full-duplex Gigabit Ethernet access services to each of over 100 users is proposed and demonstrated.
Abstract: This article proposes and demonstrates a WDM-based access network that directly connects end users over a wide area to the center node and provides guaranteed full-duplex Gigabit Ethernet access services to each of over 100 users. The center node employs an optical carrier supply module that generates not only the optical carriers for the downstream signals but also those for the upstream signals. The latter are supplied to optical network units (ONUs) at users' homes/buildings via the network. Since the ONUs simply modulate the optical carriers supplied from the center node via the network, they are wavelength-independent.

Patent
01 May 2003
TL;DR: In this article, a system for providing dynamic service using optical sub-carrier multiplexing type multi-channel access and method of controlling the same is presented, which includes a plurality of optical subcarrier MIMO modems, an optical gigabit-Ethernet switch and a plurality OFDM couplers.
Abstract: Disclosed herein is a system for providing dynamic service using optical sub-carrier multiplexing type multi-channel access and method of controlling the same. The system includes a plurality of optical sub-carrier multiplexing modems, an optical gigabit-Ethernet switch and a plurality of wavelength division multiplexing couplers. The optical sub-carrier multiplexing modems transmit user traffic using multiple optical sub-carrier channel control. The optical gigabit-Ethernet switch is connected to an access network upstream and to the optical sub-carrier multiplexing modems downstream to manage a plurality of wavelengths and a plurality of optical sub-carrier channels according to the wavelengths. The wavelength division multiplexing couplers connect the plurality of optical sub-carrier multiplexing modems with the optical gigabit-Ethernet switch, perform aggregation and branching of a certain wavelength and transmit it.

Proceedings ArticleDOI
D. Arci1, Guido Maier1, Achille Pattavina, D. Petecchi, Massimo Tornatore 
19 Oct 2003
TL;DR: This paper deals with the most common protection schemes in WDM optical networks, providing for each of them an algebraic formulation of availability analysis, and highlights some important availability relations between path-protection schemes and most relevant network parameters.
Abstract: This paper deals with the most common protection schemes in WDM optical networks, providing for each of them an algebraic formulation of availability analysis. We consider single or multiple link failure scenarios, being a link failure a fault that affects all the optical connections routed on the involved link. Availability models are applied to some numerical examples that allow us to compare the different availability degrees granted by each protection technique. When an approximation is introduced in the presented formulas, Monte-Carlo-approach simulation results are given to verify the accuracy of the theoretical analysis. The paper highlights some important availability relations between path-protection schemes and most relevant network parameters.

Proceedings ArticleDOI
01 Dec 2003
TL;DR: A hybrid optical switching approach is proposed which combines OCS and OBS to exploit the merits of both technologies, and has been evaluated in terms of throughput and blocking probability.
Abstract: Optical circuit switching (OCS) is a sophisticated technology widely deployed in current optical networks, and has many advantages in the transport of stable and long-duration traffic flows. However, it is not suitable for bursty data traffic. On the other hand, an alternative technology, optical burst switching (OBS), well addresses bursty IP traffic transport, but is not suitable for stable and large flows. To transport both types of traffic effectively, a hybrid optical switching approach is proposed which combines OCS and OBS to exploit the merits of both technologies. The performance has been evaluated in terms of throughput and blocking probability.

Patent
Gi Cheol Lee1, Jun Ho Koh1, Yun-Je Oh1
27 Oct 2003
TL;DR: In this article, the authors proposed a WDM-passive optical network (WDM-PON) that enables the integration of broadcast and communication data, in which digital broadcasting and communication services are integrated and transmitted using WDM.
Abstract: Disclosed is a wavelength division multiplexing-passive optical network (WDM-PON) that enables the integration of broadcast and communication data, in which digital broadcasting and communication services are integrated and transmitted using WDM. An optical line terminal, connected to a broadcasting network and an Internet protocol network, receives a digital broadcast signal from the broadcasting network and a first communication signal from the IP network, and transmits them as a single (broadcast/communication) integrated optical signal after their photoelectric conversion, and further transfers a second communication signal from a service user to the IP network. An optical network terminal/optical network unit on the user side transfers the integrated optical signal from the optical line terminal to the user, and transfers channel-information data of a digital broadcast desired by the user and user data including the second communication signal from the user to the optical line terminal. A first WDM demultiplexer WDM-demultiplexes the single signal and transfers it to the optical network terminal/optical network unit. A first WDM multiplexer WDM-multiplexes the user data and transfers it to the optical line terminal.

Book ChapterDOI
24 Feb 2003
TL;DR: Contrary to existing proposals for IP type communication in the optical domain light-trail node architecture also presents the first practically implementable solution to enable optical transport with mature technology, non stringent optical switching requirements, and presenting a much more cost effective alternative to electronics.
Abstract: We propose a solution for implementing a conceptual framework for IP centric communication in the optical domain. The solution, termed Lighttrails, is a combination of node architecture and protocol for realizing efficient optical communications from IP bursts to dynamic lightpaths. It is a paradigm shift from conventional optical communication modes, in supporting amongst others, very fast optical connection set up and tear down for burst of lightpaths communication, dynamic and highly bandwidth efficient sub-lambda provisioning. Light-trails also provide a first solution to optical multicasting, a key element for many of the emerging services that motivate the need for optical capacity. Contrary to existing proposals for IP type communication in the optical domain light-trail node architecture also presents the first practically implementable solution to enable optical transport with mature technology, non stringent optical switching requirements, and presenting a much more cost effective alternative to electronics.

Proceedings ArticleDOI
20 Oct 2003
TL;DR: A Light-trails solution that is applicable to mesh networks and presents the first practically implementable solution to enable optical transport with mature technology, nonstringent optical switching requirements, and potentially presents a cost effective alternative to electronics in supporting IP networks.
Abstract: Light-trails communication (Chlamtac and Gumaste, 2003) proposes a solution for implementing a conceptual framework for IP centric communication in the optical domain which is a combination of node architecture and protocol for realizing efficient optical communications from IP bursts to dynamic lightpaths. In this paper we introduce a Light-trails solution that is applicable to mesh networks. Contrary to existing proposals for IP type communication in the optical domain light-trail node architecture also presents the first practically implementable solution to enable optical transport with mature technology, nonstringent optical switching requirements, and potentially presents a cost effective alternative to electronics in supporting IP networks.

Proceedings ArticleDOI
01 Dec 2003
TL;DR: This paper proposes an inter-domain dynamic routing scheme with modest time complexity to address the problem of inter- domain dynamic routing under a multi-layer multi-domain network model.
Abstract: Next-generation optical transport networks will automatically and dynamically provision end-to-end connections. In this paper, we study the problem of inter-domain dynamic routing under a multi-layer multi-domain network model, which allows the end-to-end connections to be set up not only across multiple routing domains but also through two transport layers: the optical layer and the digital layer. In this model, a connection can traverse the domain boundary either through optical bypass or through optical-electrical-optical (O/E/O) processing. We propose an inter-domain dynamic routing scheme with modest time complexity to address the problem from an algorithmic perspective.

Proceedings ArticleDOI
19 Oct 2003
TL;DR: This paper proposes a methodology for minimizing the disruption time and the number of disruptions in the network during connection rerouting, and it is critical that the connections have minimal disruption times during network reconfiguration.
Abstract: Optical networks employing wavelength division multiplexing can carry huge volumes of traffic, hence maintaining a high level of service availability is important. This makes fault tolerance an important issue. In general the failed connections need to be rerouted. After a link or node failure, alternate paths for restoration of the failed connections may exist only if the network is reconfigured. In addition to link or node failure scenarios, connection rerouting or network reconfiguration may also prove helpful for accommodating new requests which may otherwise be blocked. Since connections on backbone optical networks, have longer call durations, it is crucial to accommodate new blocked requests through alternate means, instead of blocking them till existing connections terminate and make a path available. These situations make network reconfiguration important. Since most connections plying on todays backbone networks are high data rate connections, it is critical that the connections have minimal disruption times during network reconfiguration. In this paper, we propose a methodology for minimizing the disruption time and the number of disruptions in the network during connection rerouting.

Journal ArticleDOI
TL;DR: A novel system concept to transport microwave signals over an in-house multimode graded-index polymer optical fiber network, in order to feed the radio access points in high-capacity wireless LANs by employing optical frequency multiplying, enables cost-effective system implementation, and easy upgrading by offering data signal transparency.
Abstract: A novel system concept is presented to transport microwave signals over an in-house multimode graded-index polymer optical fiber network, in order to feed the radio access points in high-capacity wireless LANs. By employing optical frequency multiplying, the network's intrinsically limited bandwidth is overcome. The feasibility of this concept to carry data at several hundreds of Mbit/s speed for various microwave signal formats at carrier frequencies in the tens of GHz range is shown. The concept enables cost-effective system implementation, and easy upgrading by offering data signal transparency. It can readily be integrated with other system technologies such as wired Gigabit Ethernet in a single multi-service in-house polymer optical fiber network.

Patent
25 Mar 2003
TL;DR: In this article, a method and system for capacity-efficient restoration within an optical fiber communication system is proposed, where each optical fiber connection between nodes includes at least three channel groups with different priority levels for restoration switching in response to a connection failure.
Abstract: A method and system provide capacity-efficient restoration within an optical fiber communication system. The system includes a plurality of nodes each interconnected by optical fibers. Each optical fiber connection between nodes includes at least three channel groups with different priority levels for restoration switching in response to a connection failure. The system maintains and restores full-capacity communication services by switching at least a portion of the channel groups from a first optical fiber connection to a second optical fiber connection system based on the priority levels assigned to the channel groups. Service reliability is effectively maintained without incurring additional costs for dedicated spare optical fiber equipment by improving idle capacity utilization.

Proceedings ArticleDOI
29 Jun 2003
TL;DR: In this paper, the impact of impairments introduced by transparent elements present in the network, such as OADM and/or optical switches, is discussed and optimised solutions introducing low penalties proposed.
Abstract: WDM optical communication systems are evolving from simple point-to-point links to complex network architectures. In wavelength routed networks switching is performed through optical add/drop multiplexer (OADM) and optical cross-connect (OXC) nodes. These nodes provide provisioning capabilities as well as protection and restoration at the optical layer. Routing and management of the traffic demands are applied through the generalised multiprotocol label switching (GMPLS) a control plane offering intelligence at the optical layer. A central subject of debate has been the comparison of optical and electrical switching technologies, however transparent solutions offer attractive features associated with reduced unnecessary optoelectronic conversions supporting transparent networks with reduced capital and operational cost. A number of different OADM and OXC architectures based on various technologies have been proposed to date. A detailed discussion on the different architecture and technology choices supporting a variety of features are given and specific design and implementation examples are analysed. The impact of impairments introduced by transparent elements present in the network, such as OADM and/or optical switches, is discussed and optimised solutions introducing low penalties proposed. In addition, the use of novel modulation formats improving the concatenation performance of such elements is covered.

Journal ArticleDOI
TL;DR: In this paper, the tradeoffs between accumulated crosstalk and filter distortion in the context of the optical filters used in the network elements and demonstrate the balance that must be struck in the design of the filters and network system.
Abstract: The design of optical communication networks with network switching elements operating in the optical domain requires careful system analysis and potentially stringent component requirements. We consider here network elements such as transparent optical cross-connects that demultiplex WDM signals, optically switch individual channels, and then multiplex the wavelengths together again before transmission into the next span. Network element optical impairments that can significantly degrade signal quality are in-band (same wavelength) crosstalk and signal distortion from filter concatenation effects. We examine tradeoffs between accumulated crosstalk and filter distortion in the context of the optical filters used in the network elements and demonstrate the balance that must be struck in the design of the filters and network system. As an example, we study a 10-Gb/s network with 50-GHz channel spacing, examining both nonreturn-to-zero (NRZ) and return-to-zero (RZ) modulation formats. In both cases, we find optimal filter bandwidths that minimize the total signal degradation measured in terms of Q penalty, including filter misalignment statistics and signal laser frequency offset. A model is developed to treat the statistical nature of filter misalignment and its effect on filter-generated in-band crosstalk. The optical node penalties suffered by RZ signals can be significantly higher than that of NRZ signals and must be considered when estimating overall system reach.

Proceedings ArticleDOI
08 Aug 2003
TL;DR: Demand-wise shared protection bases on the diversification of demand routings and exploits the network connectivity to restrict the number of backup lightpaths needed to provide the desired level of protection.
Abstract: In this paper, a new shared protection mechanism for meshed optical networks is presented. Significant network design cost reductions can be achieved in comparison to the well-known 1+1 protection scheme. Demand-wise shared protection (DSP) bases on the diversification of demand routings and exploits the network connectivity to restrict the number of backup lightpaths needed to provide the desired level of protection. Computational experiments approve the benefits of the concept DSP for cost efficient optical network designs.

Patent
05 Feb 2003
TL;DR: In this paper, the authors proposed a flooding algorithm to share the link utilization among the remaining nodes in an optical network by calculating the link utilisation observed by the link observation section and by each remaining node.
Abstract: An optical network includes links and nodes. In each node, a control section sets an optical path to be used for optical transport. A switching section performs switching of the optical path. In the control section, a link observation section observes the wavelength of signal light that is being transmitted through a link connected to the node as the utilization of the link. A flooding section notifies each of the remaining nodes of the link utilization and acquires a link utilization observed by each of the remaining nodes so as to share the link utilization between the nodes. An optical path calculation section selects the optical path to be used for optical transport by calculation using the link utilization observed by the link observation section and the link utilization observed by each of the remaining nodes. An optical path setting section sets the optical path selected by the optical path calculation section to the optical path to be used for optical transport.

Patent
19 May 2003
TL;DR: In this article, a plurality of optical switch nodes interconnected by optical transmission fibers, or other waveguides, are configured in optical networks including multiple diverse, working routes are provided on a single fiber path interconnecting switch nodes.
Abstract: Optical systems of the present invention are configured in optical networks including a plurality of optical switch nodes interconnected by a plurality of optical transmission fibers, or other waveguides. The transmission fibers in the network can provide working and/or protection capacity for information, or communications traffic, being transmitted through the network. In various embodiments of the network, multiple diverse, working routes are provided on a single fiber path interconnecting a plurality of switch nodes. The multiple, diverse working routes can then be protected using a common protection fiber or path to provide shared protection. The switch nodes include optical switch configured to provide various levels of optical switching depending upon the network configuration. For example, line switches as well as optical cross-connects and routers can be deployed in the present invention to switch one or more wavelengths between the working and protection fibers. The optical systems can be further configured to carry lower priority traffic on the protection fibers or wavelengths during normal operation to increase the overall normal operating capacity of the system.

Patent
20 Feb 2003
TL;DR: GFP MPLS switching as mentioned in this paper is a technique that switches MPLS and non MPLS frames into GFP frames and performs MPLS functions within the GFP layer and optionally integrating with SONET/SDH/OTN cross connection functions or with Wavelength division multiplexing.
Abstract: This invention creates a method and a device to implement cheaper, faster and more efficient communications networks and Virtual Private Networks. This is achieved by placing MPLS and non MPLS frames into GFP frames and performing MPLS functions within the GFP layer and optionally integrating with SONET/SDH/OTN cross connection functions or with Wavelength division multiplexing to create the GFP MPLS device. This technique called GFP MPLS switching, switches the GFP MPLS frames as if they are MPLS frames at intermediate devices. The GFP MPLS switched circuits are optionally groomed and carried over virtually concatenated SONET/SDH/OTN circuits and multiplexed with other TDM traffic for transport over SONET/SDH/OTN or WDM.

Proceedings ArticleDOI
19 Oct 2003
TL;DR: The results show that backup-multiplexing improves the utilization of channels but requires significant computing capacity under a fixed computing capacity budget, and is useful in cases where there is little time disjointness among SLDs.
Abstract: This article addresses the problem of defining working and protection paths for scheduled lightpath demands (SLDs) in an optical transport network. An SLD is a demand for a set of lightpaths (connections), defined by a tuple (s, d, n, /spl alpha/, /spl omega/), where s and d are the source and destination nodes of the lightpaths, n is the number of requested lightpaths and /spl alpha/, /spl omega/ are the set-up and tear-down dates of the lightpaths. The problem is formulated as a combinatorial optimization problem where the objective is to minimize the number of channels required to instantiate the lightpaths. Two techniques are used to achieve this goal: channel reuse and backup-multiplexing. The former consists of assigning the same channel (either working or spare) to several lightpaths, provided that these lightpaths are not simultaneous in time. The latter consists of sharing a spare channel among multiple lightpaths. A spare channel cannot be shared if two conditions hold: a) the working paths of these lightpaths have at least one span in common and b) these lightpaths are simultaneous in time. In the other cases, the spare channel can be shared. We propose a simulated annealing (SA) based algorithm to find approximate solutions to this optimization problem since finding exact solutions is computationally intractable. The results show that backup-multiplexing improves the utilization of channels but requires significant computing capacity. Under a fixed computing capacity budget, the technique is useful in cases where there is little time disjointness among SLDs.