Abstract: A communication network comprising first and second communication paths, and nodes coupled therethrough. Each node comprises first and second switches, each having a first terminal coupled to an end of a first communication path, and a second terminal coupled to an end of a second communication path. Third terminals of the first and second switches are coupled together through at least one third communication path. A Wavelength-Division-Multiplexed device of the node is coupled to an external communication node and a fourth terminal of each switch. A node controller responds to an applied input by controlling at least one switch to cause selective coupling of at least one of (a) first and second nodes together via at least one of the paths, and (b) the external communication node and at least one of the first and second nodes via at least one of the paths.

Abstract: A reconfigurable WDM add/drop multiplexer and its method of operation at an add/drop node on an optical fiber carrying a plurality of WDM signals is described. The WDM add/drop multiplexer has a coupler and a demultiplexer element dropping WDM signals from the optical fiber to a plurality of drop terminals, and a wavelength-selective switch adding WDM signals from a plurality of add terminals onto the optical fiber. The coupler splits the WDM signals received from the optical fiber and passes the split WDM signals to the first and second output terminals. The demultiplexer element separates the split WDM signals at the plurality of drop terminals. The wavelength-selective switch, which has an input terminal for connection to the second coupler output terminal and an output terminal for connection to the optical fiber, selectively adds WDM signals on the plurality of add terminals to the optical fiber responsive to control signals.

Abstract: A communication network comprising at least one first terminal, at least one second terminal, a plurality of links, and at least first and second nodes. The first node is bidirectionally coupled to the first terminal through at least a first one of the links, and also is bidirectionally coupled to the second terminal through at least a second link and the second node. Preferably, the first node comprises a plurality of communication paths, each of which is coupled at a first end thereof to at least one corresponding first link. Second ends of the communication paths are all coupled to the second link, through a multiplexing device, and route signals between the first and second links. The first node also preferably comprises at least one alternate communication path having a first end coupled through the multiplexing device to the second link, at least one switch that is coupled to the alternate communication path, and a detector for detecting a failure in at least one of the communication paths.

Abstract: A mesh optical network node has switch cards which carry active components, such as wavelength routers to switch the paths of optical signals through the node and a fiber organizer handles the numerous optical fiber interconnections among the switch cards. The fiber organizer has no active components and can include optical paths to verify not only that a switch card connection to the fiber organizer has been made but that the connection is properly made.

Abstract: In one embodiment, first optical signal can be generated at a first end of an optical fiber segment at a first time. The first optical signal can be detected at a second end of the optical fiber segment at a second time. A second optical signal can be generated at a second end of the optical fiber segment at a third time in response to the detection of the first optical signal. The second optical signal can be detected at the first end of the optical fiber segment at a fourth time. A length of the optical fiber segment can be determined based on a difference between the second time and the first time, a difference between the third time and the second time, and a difference between the fourth time and the third time.

Abstract: A method and system for setting a variable forward error correction overhead in an optical transport network frame for an optical link at a node are disclosed. In one embodiment, a method includes selecting a forward error correction overhead, signaling an optical node the selected forward error correction overhead, and setting the forward error correction overhead in the optical network transport frame for use in transmission of data over the optical link. In one embodiment, the forward error correction overhead is complementary to the data payload to maintain total transmission rate.

Abstract: In one embodiment, an apparatus can include: (i) logic configured to detect an advanced warning indication, such as for a degraded signal condition, on a first link between first and second network devices, where the detection can utilize a number of corrected bits and forward error correction (FEC), for example; and (ii) logic configured to reroute packet traffic from the first link to a second link when the degraded signal condition is detected.

Abstract: A wavelength division multiplexed optical communication system includes a plurality of optical line terminals which may be part of separate in service networks, each having a line interface and an all-optical pass-through interface including a plurality of pass-through optical ports, and each also including a plurality of local optical ports which are connectable to client equipment and an optical multiplexer/demultiplexer for multiplexing/demultiplexing optical wavelengths. The optical multiplexer/demultiplexer may include one or more stages for inputting/outputting individual wavelengths or bands of a predetermined number of wavelengths, or a combination of bands and individual wavelengths.

Abstract: A mesh optical network node has switch cards which carry active components, such as wavelength routers to switch the paths of optical signals through the node and a fiber organizer handles the numerous optical fiber interconnections among the switch cards. The fiber organizer has no active components and can include optical paths to verify not only that a switch card connection to the fiber organizer has been made but that the connection is properly made.

Abstract: In one embodiment, techniques provide a mechanism for tracking wavelengths in a DWDM network. In particular, embodiments of the present invention also provide for connection tracking using a fast pilot tone in a DWDM network without dedicated hardware for the generation and the diction of the tone.

Abstract: Methods and apparatus for managing an optical network using pilot tones are provided. One method includes selecting an optical path having a plurality of nodes from a database defining an expected optical network. A detected list of pilot tones associated with each node of the selected optical path is generated. An expected list of pilot tones associated with each node of the selected optical path is generated. The detected and expected lists are compared to identify any mismatched nodes.

Abstract: A wavelength division multiplexed optical communication system including a first optical line interface optically coupled to a first transponder and an optical demultiplexer through which the first optical line interface is not optically coupled to the first transponder. The system also includes a second optical line interface and at least one switch. The switch is operable to optically couple the second optical line interface to (a) the first optical line interface through at least the optical demultiplexer, and alternatively (b) the second transponder. A method for an optical add/drop multiplexing system also is provided.

Abstract: The present invention provides a mechanism and a method for indirectly controlling a packet handling device interface from an optical management system in an packet-optical network. A mechanism is provided for controlling a packet handling device, such as a router, interface from a management system indirectly, by using optical equipment as a proxy and communicating between the optical gear and router via a peer-to-peer signaling protocol. The present invention provides a management method that allows separate management systems for the optical layer and the packet network layer and a method for managing the network across the domains.

Abstract: Even though network connections have priorities for reconnection and preemption of other connections upon a failure, these priorities are fixed based on the Service Level Agreement (SLA) between the Service Provider and the customer, and do not depend on the actual outage time, or downtime, during the operation of the network. Only a fixed pecking order for reconnection is guaranteed. Therefore they cannot ensure the outage a connection which experiences downtimes limited to the SLA. With the present invention, the priorities of the network connections are determined responsive to the failures of the network connections. The priorities of the network connections can also be determined responsive to the permitted downtime of the connections to better meet the SLA of the connection. Another factor in varying a network connection priority can be the expected downtime of a connection.

Abstract: The present invention provides a mechanism and a method for indirectly controlling a router interface from an optical management system in an IP-optical network. A mechanism is provided for controlling a router interface from a management system indirectly, by using optical equipment as a proxy and communicating between the optical gear and router via a peer-to-peer signaling protocol. The present invention provides a management method that allows separate management systems for the optical layer and the IP layer and a method for managing the network across the domains.

Abstract: Optical performance measurements are taken in an optical network and displayed in a form that allows an operator to enter fault information related to the measurements, or to automatically generate fault alarms to the operator, based on processing of the measurements. The optical measurements may be individual power measurements taken for each light-path at various points in each node it traverses, such as amplifiers, multiplexers/demultiplexers or at an interface with another node.

Abstract: Switching architectures for WDM mesh and ring network nodes are presented. In mesh networks, the switching architectures have multiple levels - a network level having wavelength routers for add, drop and pass-through functions, an intermediate level having device units which handle add and drop signals, and a local level having port units for receiving signals dropped from the network and transmitting signals to be added to the network. The intermediate level device units are selected and arranged for performance and cost considerations. The multilevel architecture also permits the design of reconfigurable optical add/drop multiplexers for ring network nodes, the easy expansion of ring networks into mesh networks, and the accommodation of protection mechanisms in ring networks.

Abstract: Optical performance measurements are taken in an optical network and displayed in a form that allows an operator to enter fault information related to the measurements, or to automatically generate fault alarms to the operator, based on processing of the measurements. The optical measurements may be individual power measurements taken for each light-path at various points in each node it traverses, such as amplifiers, multiplexers/demultiplexers or at an interface with another node.

Abstract: Methods and apparatus for managing an optical network using pilot tones are provided. One method includes selecting an optical path having a plurality of nodes from a database defining an expected optical network. A detected list of pilot tones associated with each node of the selected optical path is generated. An expected list of pilot tones associated with each node of the selected optical path is generated. The detected and expected lists are compared to identify any mismatched nodes.

Abstract: A way of testing a wavelength division multiplexed (WDM) system without requiring connection to data source/sink equipment. A test signal is introduced onto a light path of interest in the system, and the test signal is monitored downstream for signal integrity. Lack of signal integrity is used to identify a fault in the lightpath. Alternatively, optical loopbacks may be used to localize and identify a fault in the lightpath. The lightpath includes a source optical node connected to a sink optical node via intermediate optical nodes. An optical signal introduced at the source node with a destination at the sink node may be looped back at any one of the intermediate nodes or the sink node to localize and identify a fault in the lightpath.