A preFEC BER of a selected optical link is determined. A FEC Detected Degrade (FDD) threshold, FEC Excessive Degrade (FED) threshold, and FEC limit threshold are obtained for the selected optical link. The FDD threshold is less than the FED threshold and the FED threshold is less than the FEC limit. Based on the FDD threshold, FED threshold, the FEC limit, and a determination that a postFEC BER==0, it is determined whether a link down condition of the selected optical link can be asserted or de-asserted.

In a troubleshooting method, a controller first determines that a fault occurs on a first multi-layer link passing through a first port on a first network device, where the first multi-layer link is a link in a link aggregation group between the first network device and a second network device. The controller then releases an optical layer resource of the first multi-layer link, and deletes the first multi-layer link from the link aggregation group. The controller further establishes, a second multi-layer link for restoration of the first multi-layer link, based on a first idle port on the first network device and a second idle port on a target network device, and adds the second multi-layer link to a target link aggregation group between the first network device and the target network device.

Systems and methods include determining which services in a single Optical Transport Unit Cn (OTUCn) that is transmitted in an optical network via a plurality of optical carriers are affected by failed one or more optical carriers of the plurality of optical carriers; continuing to operate the single OTUCn with unaffected one or more optical carriers of the plurality of optical carriers; and adjusting some or all of the services from the failed one or more optical carriers to the unaffected one or more optical carriers.

Systems and methods include determining which services in a single Optical Transport Unit Cn (OTUCn) that is transmitted in an optical network via a plurality of optical carriers are affected by failed one or more optical carriers of the plurality of optical carriers; continuing to operate the single OTUCn with unaffected one or more optical carriers of the plurality of optical carriers; and adjusting some or all of the services from the failed one or more optical carriers to the unaffected one or more optical carriers.

Chromatic dispersion compensation is performed in one or more pluggable optical transceiver (POT) devices operating within an intensity-modulated direct-detection (IMDD) optical network. Compensation is performed within each POT using an electrical and/or optical chromatic dispersion module which are controlled by a set of parameters. A network computing device includes a computer processor and a host management interface for communicating with the POT. In the event of a link failure, the computer processor determines a second set of parameters to control the one or more dispersion compensation module(s) of the POT. The second set of parameters are different from a first set of parameters used to control the one or more compensation module(s) in the case of a first optical path. The computer processor causes the POT to use the second set of parameters in place of the first set of parameters.

According to various aspects of the present disclosure, an apparatus is provided. In an aspect, the apparatus includes an optical transceiver having a first port, a second port and an optical switch coupled to the first port and the second port. The optical switch is switchable between a unidirectional port operation mode and a bidirectional port operation mode. When the optical switch is in the unidirectional port operation mode, the first port is configured to send a first optical signal, and the second port configured to receive a second optical signal. When the optical switch is in the bidirectional port operation mode, the first port configured to send the first optical signal and receive the second optical signal, and the second port configured to receive a third optical signal and not send the first signal. Furthermore, a second bidirectional port operation mode is supported with the second port configured to send the first optical signal and receive the second optical signal, and the first port configured to receive a third optical signal and not send the first signal.

An optical communication system includes an optical line terminal and a plurality of optical network unit connected by optical transfer paths. The optical line terminal includes a light transmitting/receiving unit and a control unit. The light transmitting/receiving unit transmits/receives an optical signal to/from the plurality of optical network units via the optical transfer paths. The control unit performs control so as to change a launch power of an optical signal that is transmitted from the light transmitting/receiving unit, such that, when it is recognized, regarding at least one optical network unit, that a monitoring value that changes according to a receive signal quality of an optical signal transmitted from the light transmitting/receiving unit has changed to a value indicating deterioration, a receive power of an optical signal in each of the plurality of optical network units is lower than or equal to an upper limit value and a receive power of an optical signal in the optical network unit in which the monitoring value has changed to a value indicating deterioration is higher than or equal to a lower limit value.

An optical communication system includes an optical line terminal and a plurality of optical network unit connected by optical transfer paths. The optical line terminal includes a light transmitting/receiving unit and a control unit. The light transmitting/receiving unit transmits/receives an optical signal to/from the plurality of optical network units via the optical transfer paths. The control unit performs control so as to change a launch power of an optical signal that is transmitted from the light transmitting/receiving unit, such that, when it is recognized, regarding at least one optical network unit, that a monitoring value that changes according to a receive signal quality of an optical signal transmitted from the light transmitting/receiving unit has changed to a value indicating deterioration, a receive power of an optical signal in each of the plurality of optical network units is lower than or equal to an upper limit value and a receive power of an optical signal in the optical network unit in which the monitoring value has changed to a value indicating deterioration is higher than or equal to a lower limit value.

In a case where a failure occurs in a part of an optical fiber in an optical cable, when attempting to switch to a redundant configuration, the stable use of an optical transmission system is impaired, so that the wavelength band cannot be used effectively. Accordingly, the optical transmission system of the present invention includes a first optical device configured to change the transmission line of a wavelength band signal propagating through a first optical transmission line to a second optical transmission line that is the same path as the first optical transmission line, in the stage before a faulty part in the first optical transmission line, and a second optical device configured to change the transmission line of the wavelength band signal from the second optical transmission line to the first optical transmission line, in the stage after the faulty part.

Systems and methods include determining a current state of a network; determining a new state for the network having an improved cost relative to the current state; determining a defragmentation plan to move the network from the current state to the new state, the defragmentation plan including a sequence of steps; and, responsive to an event that presents an opportunity, implementing one or more steps of the sequence of steps. The implementing is conditioned on occurrence of the opportunity.