Abstract: A method of restoring an active path between two nodes of a transport network upon occurrence of a failure includes the steps of determining an alternate path through the network and establishing a path protection involving the failed active path and the alternate path. If in layered networks, a failed path is restored at a lower layer and at a higher layer concurrently, the restoration actions in the higher network layer can thus be reverted easily.

Abstract: A network element for a transport network contains a multistage lower order switching matrix with at least an input matrix stage and an output matrix stage designed to switch lower order multiplex units and with a center stage capable of switching higher order multiplex units, only, thereby connecting the input and output stages.

Abstract: The invention relates to a remote interface device (12) for terminating a remote optical fiber link, with a network input (14), a network output (15), a customer input (17) and a customer output (16) for data signals, characterized in that the device (12) is designed such that during normal operation, only data received at the customer input (17) is sent onto the network output (15), that the device (12) is further designed such that in case of a failure at the network input (14) or a failure at the hardware of the remote interface device (12), the network output (15) is closed, i.e. no signal at all is sent onto the network output (15), and in case of a failure at the customer input (17), a dedicated auxiliary signal only is sent onto the network output (15). The inventive device allows the use of the full data transfer capacity for customer's data during normal operation, and allows distinction between different types (provider, customer related) of connection failures.

Abstract: A method for the automatic activation and deactivation of a tandem connection (2-6) is provided responsive to receiving an activation or deactivation request. Prior to activation, received transmission signals are monitored (M) for an existing tandem connection to avoid creation of overlapping tandem connections. Further, responsive to receiving a deactivation request, the tandem connection sink function (SK1) is deactivated and the existing tandem connection is monitored (M1) to detect when no tandem connection information is received anymore to automatically deactivate the tandem connection source function (SO1) as well. Direct signaling of a sink inactive identifier (RDI) takes also place between the tandem connection terminating network elements (2, 6) to inform the far end tandem connection terminating network element (6) of an automatic deactivation of the tandem connection sink function (SK1).

Abstract: An 1:n or m:n path protection mechanism is provided. Rather than defining an automatic protection protocol, use is made of the existing tandem connection monitoring function, tandem connection reverse defect indication, and tandem connection trail trace identifier. Upon detection of a failure on the working path segment, the occurrence of this failure is communicated to the far end node by inserting forced RDI into the tandem connection as long as the failure persists. In the case of more than one protected paths, the failed path is identified by means of the unique trail trace identifier received on the protection path. In the case of several protection paths, one network node is defined as slave node which has to follow the switch-over initiated by the master node and choose the same protection path as the master node. Preferably, a combination of two timers enables return from failure condition to normal operation.

Abstract: The invention relates to a remote interface device (12) for terminating a remote optical fiber link, with a network input (14), a network output (15), a customer input (17) and a customer output (16) for data signals, characterized in that the device (12) is designed such that during normal operation, only data received at the customer input (17) is sent onto the network output (15), that the device (12) is further designed such that in case of a failure at the network input (14) or a failure at the hardware of the remote interface device (12), the network output (15) is closed, i.e. no signal at all is sent onto the network output (15), and in case of a failure at the customer input (17), a dedicated auxiliary signal only is sent onto the network output (15). The inventive device allows the use of the full data transfer capacity for customer's data during normal operation, and allows distinction between different types (provider, customer related) of connection failures.

Abstract: A network element for a transport network contains a multistage lower order switching matrix with at least an input matrix stage and an output matrix stage designed to switch lower order multiplex units and with a center stage capable of switching higher order multiplex units, only, thereby connecting the input and output stages.

Abstract: A method of restoring an active path between two nodes of a transport network upon occurrence of a failure includes the steps of determining an alternate path through the network and establishing a path protection involving the failed active path and the alternate path. If in layered networks, a failed path is restored at a lower layer and at a higher layer concurrently, the restoration actions in the higher network layer can thus be reverted easily.

Abstract: SONET and SDH signals are framed multiplex signals which are composed of multiplex units according to a respective specified multiplex hierarchy, such that smaller multiplex units are multiplexed in larger multiplex units and that the larger multiplex units are transmitted in frames. Compared to the multiplex hierarchy of SONET, the multiplex hierarchy of SDH has an additional level, namely the VC-4. A method of converting a SONET signal to an SDH signal is disclosed in which the multiplex units of the SONET signals are converted to corresponding multiplex units of the SDH signal, which are multiplexed into multiplex units of the additional hierarchy level. Monitoring functions are applied to both signals in accordance with the SDH multiplex hierarchy. In applying the monitoring functions to the SONET signal, the additional level of the SDH multiplex hierarchy is simulated by setting parameters to be monitored to default values.

Abstract: An 1:n or m:n path protection mechanism is provided. Rather than defining an automatic protection protocol, use is made of the existing tandem connection monitoring function, tandem connection reverse defect indication, and tandem connection trail trace identifier. Upon detection of a failure on the working path segment, the occurrence of this failure is communicated to the far end node by inserting forced RDI into the tandem connection as long as the failure persists. In the case of more than one protected paths, the failed path is identified by means of the unique trail trace identifier received on the protection path. In the case of several protection paths, one network node is defined as slave node which has to follow the switch-over initiated by the master node and choose the same protection path as the master node. Preferably, a combination of two timers enables return from failure condition to normal operation.

Abstract: Automatic control of parameters of optical components such as colored losers in a transmit side WDM system includes the following steps. At a receiver side (NE21-NE2n)) predefined characteristics of a received signal are measured. The results (MEAS) of these measurements are communicated to a remote control system (NMS1) which runs an algorithm to determine corrective adjustment parameters (ADJ) and communicates them to the transmitter side (NE11-NE1n), which adjusts the optical components accordingly. The adjustment algorithm is implemented in one of the affected network elements or in the related network management system, preferably in the element manager (NMS1) of the affected network elements. The measurements are provided automatically to the algorithm; the related adjustments are provided automatically to the network elements, which contain the transmitters to be adjusted.

Abstract: A method for the automatic activation and deactivation of a tandem connection (2-6) is provided responsive to receiving an activation or deactivation request. Prior to activation, received transmission signals are monitored (M) for an existing tandem connection to avoid creation of overlapping tandem connections. Further, responsive to receiving a deactivation request, the tandem connection sink function (SK1) is deactivated and the existing tandem connection is monitored (M1) to detect when no tandem connection information is received anymore to automatically deactivate the tandem connection source function (SO1) as well. Direct signaling of a sink inactive identifier (RDI) takes also place between the tandem connection terminating network elements (2, 6) to inform the far end tandem connection terminating network element (6) of an automatic deactivation of the tandem connection sink function (SK1).