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 transmission apparatus being one of a plurality of transmission apparatuses included in a ring network, including: a processor configured to: receive a specified message from a first transmission apparatus, the specified message being for setting loopback for at least one wavelength in a ring network, the specified message being transmitted when a failure of at least one optical signal having the at least one wavelength is detected in a specified link of the ring network, and set a loopback to a switch, the loopback being set for a specified wavelength of the at least one wavelength when a specified optical signal having the specified wavelength is terminated by the switch and converted to an electrical signal and when the specified optical signal having the specified wavelength is not terminated and not converted to an electrical signal by any apparatus from a second transmission apparatus to the specified link.

A procedure for transferring wavelengths, and a system that operates in accordance with the procedure. The system comprises at least one network terminal, each including a switch and a controller. A plurality of wavelength sets are applied to the switch. The controller is arranged to operate the switch such that the switch (a) selects at least one wavelength from at least one of the plurality of wavelength sets, based on electrical monitoring at a port module external to the network terminal, and (b) outputs the at least one wavelength to an output of the at least one network terminal.

An optical switch, comprising: a first optical waveguide, a first optical add path, a second optical add path and a micro-ring resonator. The micro-ring resonator is operable to add a first optical signal at a preselected wavelength received from the first optical add path to the first optical waveguide to travel in a first direction through the first optical waveguide. The micro-ring resonator is further operable to add a second optical signal at the preselected wavelength received from the second optical add path to the first optical waveguide to travel in a second direction through the first optical waveguide opposite to the first direction. There is also provided an optical drop switch, an optical switching apparatus, an optical communications network node and an optical communications network.

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.

Optical transceiver sharing methods may be based on different ROADM node architectures for shared restoration in flexible grid optical networks. A ROADM node architecture with a pool of transceivers may improve transceiver utilization for backup optical paths, compared to a conventional ROADM node architecture. Sharing of transceivers in the pool for working and backup optical paths may further improve transceiver utilization. The methods disclosed herein may be used for multiple bit rates and different modulation formats.

A method and apparatus for approaches for troubleshooting optical networks, particularly ROADM-based networks is described. The method includes designating a first port, of an optical communication node of a transport network, as an ingress for a loop-back optical signal to troubleshoot the transport network, designating a second port, of the optical communication node, as an egress for the loop-back optical signal, and establishing a loop-back connection between the first port and the second port to transport the loop-back optical signal.

In some aspects, an example method may include receiving, at a receiver of a first optoelectronic module, a loss of signal indicator from a second optoelectronic module that is remote from the first optoelectronic module. The method may include iteratively cycling through transmission of optical signals on a plurality of wavelength channels to the second optoelectronic module until the loss of signal indicator terminates in response to receiving the loss of signal indicator. The method may include continuing to transmit the optical signal on a particular one of the plurality of wavelength channels in response to the loss of signal indicator terminating while transmitting an optical signal on the particular one of the plurality of wavelength channels.

In some aspects, an example method may include receiving, at a receiver of a first optoelectronic module, a loss of signal indicator from a second optoelectronic module that is remote from the first optoelectronic module. The method may include iteratively cycling through transmission of optical signals on a plurality of wavelength channels to the second optoelectronic module until the loss of signal indicator terminates in response to receiving the loss of signal indicator. The method may include continuing to transmit the optical signal on a particular one of the plurality of wavelength channels in response to the loss of signal indicator terminating while transmitting an optical signal on the particular one of the plurality of wavelength channels.

An optical switch, comprising: a first optical waveguide, a first optical add path, a second optical add path and a micro-ring resonator. The micro-ring resonator is operable to add a first optical signal at a preselected wavelength received from the first optical add path to the first optical waveguide to travel in a first direction through the first optical waveguide. The micro-ring resonator is further operable to add a second optical signal at the preselected wavelength received from the second optical add path to the first optical waveguide to travel in a second direction through the first optical waveguide opposite to the first direction. There is also provided an optical drop switch, an optical switching apparatus, an optical communications network node and an optical communications network.