Abstract: Optical communication systems, terminal facilities of an optical communication system, optical communication methods, and methods of communicating within an optical network are provided. According to one aspect of the invention, an optical communication system includes: a plurality of optical communication conduits individually configured to communicate data communication signals; an optical switch adapted to optically couple a communication path of an associated data terminal with at least one of the optical communication conduits; and a controller configured to monitor the data communication signals and to control the optical switch responsive to the monitoring of the data communication signals.

Abstract: To revert the topology of a network to its original or normal state after an alternate route has been found for bypassing traffic away from a malfunctioned link that has since been repaired, an Operation Support System (OSS) sends to each of the custodial sender/chooser nodes and the tandem nodes that form the alternate route respective commands to revert the operation(s) that each node had performed during distributed restoration. The OSS is able to identify the custodial nodes by the fact that those nodes perform more operations than the tandem nodes. The operations that were performed during the distributed restoration process were recorded and the thus restored topology of the network is mapped and stored. Upon receipt from the different nodes that the malfunctioned link has been repaired, the OSS sends to each of the nodes a specific command to perform the inverse of the operation(s) that that node had performed during the restoration.

Abstract: A method and apparatus for restoration of unrestored links and nodal failures utilizes a combination of link and path restoration schemes and most existing message types. This invention begins by using a link restoration scheme, when a fault is detected, to designate a pair of custodial sender and chooser. The conventional link restoration scheme then seeks to find an alternate route to reroute the disrupted traffic. When no alternate route is found after a given time period, a special signal is sent out to notify the network that a path restoration is to take place. The communications path on which the failure occurred is identified. Thereafter, data that was stored in the nodes is retrieved to identify the two ends nodes of the communications path. A restoration process then takes place to find alternate paths to replace the failed communications path.

Abstract: In a self healing network (SHN) distributed restoration algorithm (DRA) scheme, in the case where two adjacent tandem nodes are contending for the same spare link, an arbitration scheme is used to determine which tandem node has the right to reserve the spare link for its use. The arbitration scheme entails a pre-event knowledge by each of the tandem nodes of the transmission time therebetween. A tandem node link arbitration timer in each of the adjacent nodes provides a predefined time period for which a node can compare whether it had begun sending out its flooding signature before the far end node had sent out its. Thus, when a node detects a newly arrived signature received from the spare link that connects the node to its far end node, and if this newly arrived signature is detected before the predefined time period has elapsed, then the node will give up the spare link for the use of the far end node.

Abstract: To verify that a communications path restored in response to a failure to a telecommunications network is a validly restored path, each of the end nodes terminating the restored communications path sends out a message containing data that identifies that node and the ID of the access/egress port to which the STS-1 circuit forming the communications path is connected. Once the respective path verification messages are exchanged between the two end nodes of the communications path, the Operations Support System (OSS) that oversees the topology of the network retrieves those messages and compares the data contained therein with the data of the same type of messages from the same ends nodes that were stored just prior to the occurrence of the disruption to the communications path. The restored communications path is deemed to be verified if there are no differences between the path verification messages retrieved after the failure event and the path verification messages stored just prior to the failure event.

Abstract: To estimate an optimal amount of spare capacity for a network so that efficient distributed restoration of the network can take place in the event of a network failure, parameter assumptions and network design guidelines are provided to a network modeling tool to generate a desirable amount of spare links for the network. The spare links are allocated to the different nodes of the network. After a failure in the network, the result of the restoration of the network due to the failure is reported to the controller of the system. If necessary, the parameter assumptions and network design guidelines are updated and fed back to the network modeling tool for further refining the spare capacity of the network. An optimal amount of spare capacity is thus achieved by a continuous redeployment of the spare capacity output provided by the network modeling tool. Simulated failures and subsequent restorations of the network are provided to an exerciser periodically.

Abstract: The present invention provides to a distributed restoration scheme a set of timers so that multiple senders and choosers can more fairly contend for the spare capacity of a telecommunications network. In particular, a preactivation timer would force a sender that had reserved excess spare capacity of the network for restoring its own failed links to release any unused spare capacity prior to the time that it terminates its operation, provided that it has found an alt-route or alt-routes for its failed link. An alarm validation timer and a hold off timer in the invention scheme further provide for respective validation and detection that a detected fault is not transient or intermittent in nature and that a restoration process is needed to find the alt-routes.

Abstract: To verify that a communications path restored in response to a failure to a telecommunications network is a validly restored path, each of the end nodes terminating the restored communications path sends out a message containing data that identifies that node and the ID of the access/egress port to which the STS-1 circuit forming the communications path is connected. Once the respective path verification messages are exchanged between the two end nodes of the communications path, the Operations Support System (OSS) that oversees the topology of the network retrieves those messages and compares the data contained therein with the data of the same type of messages from the same ends nodes that were stored just prior to the occurrence of the disruption to the communications path. The restored communications path is deemed to be verified if there are no differences between the path verification messages retrieved after the failure event and the path verification messages stored just prior to the failure event.