An optical communications network has an interconnecting node (100) coupled in between at least one hub node (130) and at least first (140) and second (150) access nodes, to provide working and protection optical paths. The interconnecting node has a working wavelength selective switch (110) to select which working wavelengths are coupled. A corresponding protection wavelength selective switch (120) is also provided for the protection wavelengths. In the event of detection of a fault, protection switching (230) is carried out at the access node and the hub node without altering the selections made by the wavelength selective switches in the interconnecting node. Thus protection schemes across the interconnecting node for more than one access node can be handled. By not needing to alter wavelength selections at the interconnecting node during protection switching operation, the complexity and thus costs can be reduced.

A method, in a node operating in a network with a control plane, to optimize wavelength retuning on service redials, includes detecting a failure on a link associated with the node; and, for each affected connections on the link, sending a respective release message to an associated originating node via the control plane, the release message including a protect path and a wavelength, wherein the release message is utilized by the associated originating node to redial the affected connections with the protect path and the wavelength determined by the node, to minimize wavelength retuning on the affected connections.

In some embodiments, an apparatus includes an optical transceiver that includes a first set of electrical transmitters operatively coupled to a switch. Each electrical transmitter from the first set of electrical transmitters is configured to transmit an electrical signal from a set of electrical signals. In such embodiments, the switch is configured to switch an electrical signal from the set of electrical signals such that the set of electrical signals are transmitted via a second set of electrical transmitters. Each electrical transmitter from the second set of electrical transmitters is operatively coupled to an optical transmitter from a set of optical transmitters. The set of optical transmitters is operatively coupled to an optical multiplexer. In such embodiments, at least one electrical transmitter from the second set of electrical transmitters is associated with a failure within the optical transceiver.

A multi-failure resolution optical node includes an operating system wavelength path and two or more standby system wavelength paths which are assigned to the operating system wavelength path and have been assigned a ranking. It further includes a node control unit that can separately operate the operating system wavelength path and the standby system wavelength paths in a normal power consumption mode or a reduced power consumption mode. Thus, it is possible to provide an optical node with which power consumption is reduced and with which switching to a standby system wavelength path can be performed quickly in response to a failure in the operating system wavelength path.

There is provided an optical transmission device including a light source configured to generate light used for coherent detection processing of reception light; a monitor configured to monitor a frequency offset between the reception light having a plurality of protection wavelengths and the light generated by the light source, based on a signal obtained by the coherent detection processing of the reception light having the plurality of protection wavelengths available for a work wavelength by the light generated by the light source; and a controller configured to select a protection wavelength to be switched to the work wavelength among the plurality of protection wavelengths, based on the frequency offset monitored by the monitor.

An optical path route design device includes a transmission/reception route selection unit, a candidate selection unit, an existence judgement unit, a maximum resource 3R selection unit, and a new 3R selection unit. The design device selects relay stations in which two transmission/reception end points are arranged, selects a route pair of an active system-0 route and a standby system-1 route, which connects the transmission/reception end points with each other and does not overlap each other, and a backup third route detouring from the route pair via one or more relay stations, and arranges a resource amount of predetermined wavelengths in a shared 3R which is on the third route and shared by a plurality of route pairs.