The present invention includes novel techniques, apparatus, and systems for optical WDM communications. Tunable lasers are employed to generate respective subcarrier frequencies which represent subchannels of an ITU channel to which client signals can be mapped. In one embodiment, subchannels are polarization interleaved to reduce crosstalk. In another embodiment, polarization multiplexing is used to increase the spectral density. Client circuits can be divided and combined with one another before being mapped, independent of one another, to individual subchannels within and across ITU channels. A crosspoint switch can be used to control the client to subchannel mapping, thereby enabling subchannel protection switching and hitless wavelength switching. Network architectures and subchannel transponders, muxponders and crossponders are disclosed, and techniques are employed (at the subchannel level/layer), to facilitate the desired optical routing, switching, concatenation and protection of the client circuits mapped to these subchannels across the nodes of a WDM network.

Disclosed herein is a method of transmitting a data stream from a first location to a second location through an optical network, as well as a corresponding performance monitoring unit, a transmitting arrangement and a receiving arrangement. The method comprises the steps of transmitting said data stream from said first location to said second location along a working path, wherein said data stream is transmitted in the form of a super channel comprising a number of n wavelengths within a predefined reserved wavelength range, monitoring the performance of the transmission based on the super channel signal received at said second location, and in case the performance is observed to drop below a predetermined performance threshold, unburdening the super channel from a part of said data stream while maintaining the reserved wavelength range for said super channel, by redirecting said part of the data stream for transmittal along at least one restoration path connecting said first and second locations, and transmitting the remainder of said data stream within the super channel on a number of wavelengths that is less than n, and/or with a reduced transmission rate for at least some of the wavelengths in said super channel.

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.

This disclosure describes devices and methods related to multiplexing optical datasignals. A method may be disclosed. The method may comprise receiving, by a dense wave division multiplexer (DWDM), one or more optical data signals. The method may comprise combining, by the DWDM, the one or more optical data signals. The method may comprise outputting, by the DWDM, the combined one or more optical data signals to a first circulator. The method may also comprise combining, by the WDM, the second optical data signal and one or more third signals, and outputting an egress optical data signal to an optical switch. The method may also comprise outputting, by the optical switch, the egress optical data signal on a primary fiber.

A method for assigning a severity to failure indications of network resources in a multilayered communication network includes in a processor, receiving one or a plurality of failure indications related to a failure of one or more network resources from a plurality of network resources in a communication network. A severity may be assigned to the one or said plurality of failure indications based on an impact on data, wherein assigning the severity includes at least one of: assigning a static severity based on a single traffic impact assessment in the communication network due to the one or more failed network resources, and assigning a dynamic severity based on continuous or periodic traffic impact assessments in the communication network due to the one or more failed network resources. The severity of the one or said plurality of failure indications may be outputted on an output device.

A branching unit branches a first wavelength-multiplexed optical signal input through a first transmission line, the first wavelength-multiplexed optical signal including first and second optical signals. A wavelength selection unit receives the branched first wavelength-multiplexed optical signal branched by the branching unit, receives a second wavelength-multiplexed optical signal including a third optical signal in the same band as that of the first optical signal and a fourth optical signal in the same band as that of the second optical signal through a second transmission line, outputs a third wavelength-multiplexed optical signal including the first and fourth optical signals optical to a third transmission line and output the third optical signal. A multiplexing unit outputs a fourth wavelength-multiplexed optical signal in which the branched first wavelength-multiplexed optical signal branched by the branching unit and the third optical signal output from the wavelength selection unit are multiplexed to a fourth transmission line.

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.

A network element includes a client port configured to receive a signal for transmission; a line port configured to transmit the signal to a far end via Optical Transport Network (OTN); circuitry configured to communicate one or more of a fault and a status associated with the signal to the far end via OTN overhead. The circuitry configured to communicate can be for the fault and utilizes one or more Tandem Connection Monitoring (TCM) layers in the OTN overhead. The circuitry configured to communicate can be for the status and utilizes one or more of Optical Data Unit (ODU) Performance Monitoring (PM) and one or more Tandem Connection Monitoring (TCM) layers.

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.