Optical Transport Network

About: Optical Transport Network is a research topic. Over the lifetime, 6055 publications have been published within this topic receiving 85783 citations.

FEC in optical communications - A tutorial overview on the evolution of architectures and the future prospects of outband and inband FEC for optical communications

Abstract: The recent establishment of the 10/40 Gbps technology in DWDM optical links heralds a new era of bandwidth abundance, in response to an explosive growth of services provided through the Internet. Forward error correction (FEC) is one of the key-enabling elements in this long-awaited achievement. Borrowed from the wireless world, FEC was initially introduced in wavelength-division multiplex (WDM) optical-systems to combat amplified spontaneous emission (ASE), a form of noise native in optical amplifiers (OAs). These first generation FEC systems have been associated with a coding-gain of approximately 6 dB. However, as transmission rates gradually scaled towards 10 Gbps, other optical-impairments gained in significance, primarily nonlinear (NL) effects but also chromatic-dispersion (CD) and polarization mode dispersion (PMD). FEC turned out to be invaluable in mitigating these impairments as well

Optical Networks: Third Generation Transport Systems

Abstract: Preface. 1. Introduction. Three Generations of Digital Transport Networks. All Features Are Not Yet Available. Optical Fiber Capacity. A Brief Introduction to WDM and TDM. Combining WDM and TDM. The Optical Marketplace. The Local Loop Bottleneck Must Be Solved. Expansion of Network Capacity. Wireless Optical Systems. Key Optical Nodes. Key Terms for the Cross-connect. Other Key Terms. Another Look at the Optical Node. Evolution of Optical Systems. Key Attributes of Optical Fiber. Summary. 2. The Telecommunications Infrastructure. The Local Connections. The Backbone Connections. The Digital Multiplexing Hierarchy. The Digital Signaling Hierarchies. T1 or DS1 T3 or DS3? The Layered Protocol Model in the Transport Network. Considerations for Interworking Layer 1, Layer 2, and Layer 3 Networks. Summary. 3. Characteristics of Optical Fiber. The Basics. The Wavelength. The Basic Components. The Source of the Signal. The Detector. Structure of the Fiber. Angles. Fiber Types. Key Performance Properties of Fiber. Attenuation. Amplifier Spontaneous Emission (ASE). Chromatic Dispersion. Polarization-mode Dispersion (PMD). Lasers. Summary. 4. Timing and Synchronization. Timing and Synchronization in Digital Networks. Effect of a Timing Error. The Clocking Signal. Types of Timing in Networks. The Synchronous Clock Hierarchy. Timing Variations. Frequency Accuracy. Methods of Clock Exchange. Free-Running. Line-Timed. Loop-Timed. External. Through-Timed. Distribution of Timing Using SONET and DS1. Timing Downstream Devices. The Building Integrated Timing Supply (BITS). Synchronization Status Messages (SSMs) and Timing Loops. Summary. 5. SONET and SDH. How SONET and SDH Came into Being. Participation by ITU-T. Reasons for Success of SONET/SDH. The SONET Multiplexing Hierarchy. SONET and SDH Multiplexing Structure. The SONET/SDH Frame Structure. Rationale for the 51.840 Mbit/s Envelope. Overhead and User Areas in the Envelope. SONET and SDH Functional Components. SONET and SDH Problem Detection. Locating and Adjusting Payload with Pointers. Virtual Tributaries in More Detail. Virtual Tributaries and Virtual Containers. The Overhead Bytes. SONET and SDH Concatenation. Summary. 6. Architecture of Optical Transport Networks (OTNs). The Digital Wrapper. Control Planes. In-band and Out-of-band Control Signaling. An In-band Signal on an O/O/O PXC. Importance of Multiplexing and Multiplexing Hierarchies. Current Digital Transport Hierarchy. SONET Multiplexing Hierarchy. SDH Multiplexing Hierarchy. Revised SDH Transport Hierarchy. Key Indexes and Other Terms. The New Optical Transport and Digital Transport Hierarchy. ODUk Mapping and Multiplexing. The OTN Layered Model. Another View. Full Functionality Stack: OTM-n.m. Reduced Functionality Stack: OTM-nr.m and OTM-0.r. Encapsulation and Decapsulation Operations. Generic Framing Procedure (GFP). Summary. 7. Wavelength Division Multiplexing (WDM). The WDM Operation. Dense Wave Division Multiplexing (DWDM). TDM and WDM Topologies. Relationship of WDM to SONET/SDH. Erbium-doped Fiber (EDF). WDM Amplifiers. Gain Flatness. Add-Drop Multiplexers. WADM Input and Output Ports. WDM Cross-connects. Wavelength Continuity Property. Example of DWDM Wavelength Plan. Average Versus Maximum Span Loss and Chromatic Dispersion. Higher Dispersion for DWDM. Tunable DWDM Lasers. Summary. 8. Network Topologies and Protection Schemes. The Non-negotiable Requirement: Robust Networks. Diversity in the Network: Which Control Plane? Line and Path Protection Switching. Types of Topologies. Working and Protection Fibers. Point-to-Point Topology. 1:N Protection Channel Sharing. Optical Channel Concatenation. Bi-directional Line-Switched Ring (BLSR). Protection Switching on Four-Fiber BLSR. Meshed Topologies. Passive Optical Networks (PONs). Optical Ethernets and Ethernet PONs. Ethernet in the Wide Area Backbone? Metro Optical Networking. Summary. 9. MPLS and Optical Networks. What IS Label Switching? Reasons for Using Label Switching. The Forwarding Equivalence Class (FEC). Scalability and Granularity: Labels and Wavelengths. Types of MPLS Nodes. Label Distribution and Binding. Methods for Label Distribution. Label Swapping and Traffic Forwarding. MPLS Support of Virtual Private Networks (VPNs). MPLS Traffic Engineering (TE). Traffic Oriented or Resource Oriented Performance. Traffic Trunks, Traffic Flows, and Label Switched Paths. LDP, CR-LDP, RSVP-TE, and OSPF (Extensions) for TE Support. Multiprotocol Lambda Switching (MPlS). Relationships of OXC and MPLS Operations. MPLS and Optical Wavelength Correlation. Failure of the Optical Connection. MPLS and Optical TE Similarities. Possibilities for the MPlS Network. Control and Data Planes Interworking. Summary. 10. Architecture of IP and MPLS-based Optical Transport Networks. IP, MPLS, and Optical Control Planes. The Internet Control and Data Planes. The MPLS Control and Data Planes. The Optical Control and Data Planes. Interworking the Three Control Planes. Management of the Planes. Diverse Views on Control Planes' Interworkings. A Framework for IP over Optical Networks. Two General Models. Domain Services Model. Unified Service Model. Interconnections for IP over Optical. An Opposing View. Which Approaches to Use? Generalized MPLS (GMPLS) Use in Optical Networks. Considerations for Interworking Layer 1 Lambdas and Layer 2 Labels. Examples of GMPLS Operations. Suggested Labels for the Wavelengths. Bi-directional LSPs in Optical Networks. Link Protection. The Next Horizon: GMPLS Extensions for G.709. Technology Independent Part. Technology Dependent Part. OTM Overhead Signal (OOS). Transparency. G.709 Label Space. OCh Label Space. Applications. ODUk General Communication Channel (GCC). A More Immediate Horizon: GMPLS with SONET and SDH. Traffic Parameters. Summary. 11. The Link Management Protocol (LMP). Keep the Optical Link Up and Running. What is Managed. Data-bearing Links. Clarification of Terms. Basic Functions of LMP. LMP Messages. LMP Message Header. LMP TLVs. The Fields in the LMP Messages. Control Channel Management. Parameter Negotiation. The Hello Protocol. Link Property Correlation. Link Connectivity Verification. Fault Management. Extending LMP Operations for Optical Link Systems (OLSs). Link Summarization. Fault Management. Trace Monitoring. Summary. 12. Optical Routers: Switching in Optical Internets. The State of the Art in Optical Switching. Order of Preferences in Switching Implementations. Clarification of Key Terms. One Aftermath of September 11: Increasing Load on the Transport Networks. Evolution of Switching Technologies. The Speeds of Electronics and Photonics. An Optical Router. The Control Element. Optical Switching Technologies. Optical Resources. MicroElectroMechanical Systems (MEMS). Protecting the Label Switched Path. Protection of the Optical Switched Path (OSP). Correlating the Wavelength OSP with the MPLS LSP. Setting up the OSPs and LSPs Between Nodes H, I, and J. Setting Up a Protection Path Between Nodes H, G, and J. Recovery and Use of Protection Path. Expanding the Roles of Nodes G and I. Nesting the LSPs and OSPs. Topology Choices for a Node Failure. Plane Coupling and De-coupling. Some End-to-End Wavelengths and Some Node-to-Node Wavelengths. Granularity of Labels vs. Wavelength Support. Approach to the Problem of LSP and OSP Interworking. MEMS and Optical Switching Re-examined. Thermo-optic Switches. Bubble Switches. Summary. 13. ASON Operations at the User Network Interface (UNI) and the Network-to-Network Interface (NNI). Objectives of the ASON. The UNI and the NNI. Managing the Optical Bandwidth in the ASON. The General Approach to Optical Bandwidth Management. IETF Optical Carrier Framework for the UNI. Focus on OC-48/STM-16 and Above. UNI-SR (Subrates). Types of Connections. Connection Attributes. Identification Attributes. Connection Characteristic Attributes. Routing Constraints Attributes. The Network-to-Network Interface (NNI). NNI Signaling Requirements. Neighbor Discovery. NNI Topology and Resource Distribution Protocol. NNI Protocol Mechanisms. UNI and NNI Signaling Services. Summary. 14. ATM vs. IP in Optical Internets. IP over ATM over SONET. The OSI and Internet Layered Models. Placement of Core Protocols. PPP and L2TP. ATM in the SONET/SDH Payload Envelope. PPP in the SONET Payload Envelope. Prevalent Approach in Today's Internets. Encapsulation/Framing Rules. ATM and Frame Relay Framing Formats. Encapsulation Field Values. Encapsulation Options with SNAP. The PPP Packet. The ATM vs. IP Debate. Overhead of IP and ATM. Is the ATM Overhead Tolerable? Three Encapsulation Methods. Method 1: Conventional Approach. Method 2: Lightweight PPP. Method 3: Eliminating ATM. Summary. 15. Optical Internets: Evolving to a 3G Architecture. Migration to IP Optical Networking. IP and the Optical Backbone. Example of IP and l Forwarding. IP Subnets. Support of Non-optical Nodes. Placing MPLS into the Picture. Putting It Together. IP Routing Table. MPLS Cross-connect Table: Interface A. Optical Cross-connect Table: Interface A. Optical Cross-connect Table: Interface B.

Self-healing optical network

Abstract: A self-healing optical network carrying traffic between first and second optical linear terminals (NODE A, NODE B, NODE C, NODE D). The self-healing optical network including first, second, and third optical switching units (210, 216, 226, 232), first, second, and third spare optical channels (214, 220, 222, 228), and a working optical channel (212, 218, 224, 230). The first, second, and third optical switching units are coupled in a ring configuration using said first, second, and third spare optical channels. The first and second optical switching units are coupled by the first spare optical channel and by the working optical channel. The first and second optical switching units each direct the traffic between the first and second optical linear terminals along the working optical channel or along the second and third spare optical channels in the event the working optical channel is not available.

Communication of signals sharing a single optical source

Abstract: A single optical source is shared by a plurality of optical communication paths to communicate different information signals on the different paths. A high power optical carrier generator provides a carrier signal to an optical multiplexer. The multiplexer splits the optical carrier into a plurality of paths, each including an external optical modulator. The external optical modulator in each path is used to modulate the carrier in its respective path by a desired information signal. An additional modulated optical carrier can be coupled to one or more of the optical communication paths for the communication of additional information such as a standard set of television channel signals in a cable television network.

Optical communication network apparatus and optical switching network

Abstract: An optical communication network node apparatus including input terminals 111 to 11n, 1:2 optical branch units 121 to 12n, a pass-through optical switching network d101, 2:1 optical connectors 151 to 15n, output terminals 171 to 17n, a drop optical switching network 102, output interfaces 13-1 to 13-mn, input interfaces 14-1 to 14-mn and an insert optical switching network. Accordingly, in the optical communication network node apparatus, various types of optical switching networks are separated from one another and each optical switching network supports only a necessary switching state, so that the number of optical switch elements can be reduced.