Multiple network controllers are interconnected in a full mesh structure, e.g., through a cyclical cross connector, to form a distributed control system for a network of a large number of nodes. A network controller acquires characterizing information of links emanating from a respective set of nodes, communicates the information to each other network controller, and determines a route set from each node of the respective set of nodes to each other node of the network. The network controller may determine, for each link included in the route set, identifiers of specific route sets which traverse the link. Accordingly, a state-change of any link in the network can be expeditiously communicated to network controllers to take corrective actions where necessary. A network controller may rank routes of a route set according to some criterion to facilitate selection of a favourable available route for a connection.

An apparatus includes a reconfigurable optical add/drop multiplexer (ROADM) having an input port to receive a first optical signal from a second device. The ROADM also includes a first wavelength selective switch (WSS), in optical communication with the input port, to convert the first optical signal into a second optical signal, a loopback, in optical communication with the first WSS, to transmit the second optical signal, and a second WSS, in optical communication with the loopback, to convert the second optical signal to a third optical signal and direct the third optical signal back to the second device via the input port.

A system, apparatus, and method for an optical grooming network; wherein a set of switches form an optical grooming interconnection system where each switch is communicatively coupled to each other switch; a set of clients; where each switch of the set of switches is communicatively coupled to a client of the clients; wherein each client receiver is enabled to communicate through the set of switches to any client or modem; and a set of coherent optical modems; wherein each coherent optical modem is communicatively coupled to a switch of the set of switches; wherein each client of the clients is able to communicate through the set of switches to every coherent optical modem of the set of coherent optical modems, and each coherent optical modem in the set of coherent optical modems can communicate to every coherent optical modem of the set of coherent optical modems.

A control apparatus includes an optical wavelength change control unit that specifies, in response to a request to change a wavelength band of a first optical wavelength path used by a first transmission apparatus and a second transmission apparatus to a wavelength band of a second optical wavelength path, a first route between routers which is affected by the request and a service which uses the first route and that specifies a second route between the routers which detours the specified service; a router control unit that transmits a request to detour the specified service to the second route, to a start-point router and an end-point router on the first route; and a transmission apparatus control unit that transmits a request to change the wavelength band of the first optical wavelength path to the wavelength band of the second optical wavelength path, to the first transmission apparatus and the second transmission apparatus.

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.

A method including storing, by a first device in a mesh network, stored connection state information associated with an outgoing communication transmitted by the first device; determining, by the first device, observed connection state information based at least in part on receiving an incoming communication from a second device in the mesh network; comparing, by the first device, the observed connection state information with the stored connection state information; and selectively processing, by the first device, the incoming communication based at least in part on a result of the comparing. Various other aspects are contemplated.

An apparatus includes a reconfigurable optical add/drop multiplexer (ROADM) having an input port to receive a first optical signal from a second device. The ROADM also includes a first wavelength selective switch (WSS), in optical communication with the input port, to convert the first optical signal into a second optical signal, a loopback, in optical communication with the first WSS, to transmit the second optical signal, and a second WSS, in optical communication with the loopback, to convert the second optical signal to a third optical signal and direct the third optical signal back to the second device via the input port.

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.

An apparatus includes a reconfigurable optical add/drop multiplexer (ROADM) having an input port to receive a first optical signal from a second device. The ROADM also includes a first wavelength selective switch (WSS), in optical communication with the input port, to convert the first optical signal into a second optical signal, a loopback, in optical communication with the first WSS, to transmit the second optical signal, and a second WSS, in optical communication with the loopback, to convert the second optical signal to a third optical signal and direct the third optical signal back to the second device via the input port.

An apparatus includes a reconfigurable optical add/drop multiplexer (ROADM) having an input port to receive a first optical signal from a second device. The ROADM also includes a first wavelength selective switch (WSS), in optical communication with the input port, to convert the first optical signal into a second optical signal, a loopback, in optical communication with the first WSS, to transmit the second optical signal, and a second WSS, in optical communication with the loopback, to convert the second optical signal to a third optical signal and direct the third optical signal back to the second device via the input port.