An optical network having a first terminal node, a second terminal node, and a network service system is described. The first terminal node has a plurality of ports and a signal restoration component to create a restored path. The second terminal node has a plurality of ports and a failure monitor to issue a path failure notice. A working path, a protection path, and the restored path are each fiber optic lines optically coupling the first terminal node to the second terminal node to enable a service, each path requiring a quantity of exclusive licenses. The network service system receives a path failure notice indicating a working path failure, calculates the quantity of licenses required by the restored path, releases the quantity of licenses required by the working path and applies at least a portion of the quantity of licenses to the quantity of licenses required by the restored path.

A path protection method includes receiving, by a source node of a first path, a path event notify message from a first node on the first path. The path event notify message includes indication information that the first path is predicted to fail. The path protection method further includes obtaining, by the source node, information about a predicted protection path. The information about the predicted protection path includes resource information of a second path useable to protect a service on the first path. The first path and the second path include the source node and a same sink node. The path protection method further includes storing, by the source node, the resource information of the second path.

An example system includes a first network device having first circuitry. The first network device is configured to perform operations including receiving data to be transmitted to a second network device over an optical communications network, and transmitting first information and second information to the second device. The first information is indicative of the data, and is transmitted using a first communications link of the optical communications network and using a first subset of optical subcarriers. The second information is indicative of the data, and is transmitted using a second communications link of the optical communications network and using a second subset of optical subcarriers. The first subset of optical subcarriers is different from the second subset of optical subcarriers.

An example system includes a first network device having first circuitry. The first network device is configured to perform operations including receiving data to be transmitted to a second network device over an optical communications network, and transmitting first information and second information to the second device. The first information is indicative of the data, and is transmitted using a first communications link of the optical communications network and using a first subset of optical subcarriers. The second information is indicative of the data, and is transmitted using a second communications link of the optical communications network and using a second subset of optical subcarriers. The first subset of optical subcarriers is different from the second subset of optical subcarriers.

There is provided an apparatus for fiber optic line continuity detection. The apparatus comprises an optical input connectable to a first optical fiber of a fiber optic line, an optical output connectable to a second optical fiber of the fiber optic line an optical interface unit configured to transmit and receive optical signals; and an optical switch having a first configuration and a second configuration. In the first configuration the optical switch is configured to pass optical signals received at the optical input to the optical interface unit and to pass optical signals received from the optical interface unit to the optical output. Whereas, in the second configuration the optical switch is configured to pass optical signals received at the optical input to the optical output.

An optical network having a first terminal node, a second terminal node, and a network service system is described. The first terminal node has a plurality of ports and a signal restoration component to create a restored path. The second terminal node has a plurality of ports and a failure monitor to issue a path failure notice. A working path, a protection path, and the restored path are each fiber optic lines optically coupling the first terminal node to the second terminal node to enable a service, each path requiring a quantity of exclusive licenses. The network service system receives a path failure notice indicating a working path failure, calculates the quantity of licenses required by the restored path, releases the quantity of licenses required by the working path and applies at least a portion of the quantity of licenses to the quantity of licenses required by the restored path.

The present invention proposes a new method for solving the problem of fault tolerance. This new approach obtains all secondary routes assigned to each possible connection (user). The secondary routes replace the main routes when these are affected by at least one fault, which keeps the users connected as long as, for each connection, there is at least one route with operative links for reaching the destination nodes thereof. This new approach solves the general case of an arbitrary set of simultaneous link failures. The method also assesses the number of wavelengths for each link of the network, so that the probability of any connection request from a determined user c being blocked is less than a predefined threshold β.sub.c, despite the possible occurrence of the fault scenario.

Systems, methods, and computer-readable media are provided for signaling the presence of a fault in a multi-band optical network or other communication system. In response to a detected fault in a multi-band communication system impacting a specific band of the multi-band communication system, a method, according to one implementation, may include a step of creating a fault signal corresponding to the detected fault. The method may also include the step of conveying the fault signal to at least one of an upstream controller and a downstream controller of the multi-band communication system to trigger an action for handling the fault on the specific band. The action may be handled independently of other actions associated with one or more other bands of the multi-band communication system.

An optical branching/coupling device includes: a first optical branching unit that splits first light with a first and a second wavelength, and outputs second light and third light; a wavelength selector that receives the second light, receives fourth light with a third wavelength, output fifth and sixth light, one of the fifth light and the sixth light including an optical signal of the first wavelength of the second light and including the fourth light, and the other including an optical signal of the second wavelength; a first light switch that receives the fifth light and the sixth light, output one of the fifth light and the sixth light as seventh light, and output the other as eighth light; and a second light switch that receives the third light, receives the eighth light, and outputs the third or the eighth light that have been input as ninth light.

Systems and methods include receiving first power snapshot from a receiving end of a foreign controlled link of the one or more foreign controlled optical links when there are no faults thereon; responsive to obtaining second power snapshot from the receiving end of the foreign controlled link, detecting a fault on one of at least one channel and part of the spectrum traversing the foreign controlled link; correlating the second power snapshot with the first power snapshots; and raising an indication of fault for the foreign controlled link based on the correlating.