Systems and methods are provided for creating a sequence of turn-up processes for amplifiers. A method, according to one implementation, includes determining when a fiber span is initially installed in an optical line system or when an Optical Line Failure (OLF) in the fiber span has recovered. The optical line system includes a first set of amplifiers deployed at an upstream node and a second set of amplifiers deployed at a downstream node, the upstream node connected to the downstream node via the fiber span. In response to determining that the fiber span is initially installed in the optical line system or that an ORL in the fiber span has recovered, the method also includes sending a flag from the upstream node to the downstream node to allow the first set of amplifiers to perform a first turn-up process before the second set of amplifiers perform a second turn-up process.

Systems and methods are provided for creating a sequence of turn-up processes for amplifiers. A method, according to one implementation, includes determining when a fiber span is initially installed in an optical line system or when an Optical Line Failure (OLF) in the fiber span has recovered. The optical line system includes a first set of amplifiers deployed at an upstream node and a second set of amplifiers deployed at a downstream node, the upstream node connected to the downstream node via the fiber span. In response to determining that the fiber span is initially installed in the optical line system or that an ORL in the fiber span has recovered, the method also includes sending a flag from the upstream node to the downstream node to allow the first set of amplifiers to perform a first turn-up process before the second set of amplifiers perform a second turn-up process.

A polarization recovery device comprises an input that receives a first optical signal with unknown polarization and with at least one signal parameter at an initial value, a first output that outputs a second optical signal with known polarization and with the at least one signal parameter at or near the initial value, and a recovery block that generates the second optical signal based on the first optical signal.

A polarization recovery device comprises an input that receives a first optical signal with unknown polarization and with at least one signal parameter at an initial value, a first output that outputs a second optical signal with known polarization and with the at least one signal parameter at or near the initial value, and a recovery block that generates the second optical signal based on the first optical signal.

A transponder includes a multiplexing section, optical transmitters, optical receivers, an extracting section, and a warning monitor section, wherein the extracting section includes a first signal extracting unit for extracting reception data, a second signal extracting unit for extracting reception data, and a reception signal switching section. When carrier signals are in a link-establishable state, the reception signal switching section supplies reception electric signals generated by the optical receivers to the first signal extracting unit and outputs the reception data. When a carrier signal is in a non-link-establishable state, the reception signal switching section supplies a reception electric signal generated by an optical receiver using a carrier signal in the link-establishable state to the second signal extracting unit and outputs the reception data extracted by the second signal extracting unit.

An optical transmission apparatus outputs a main signal. An optical transmission apparatus superimposes a monitoring signal on an optical signal and outputs it. A submarine branching apparatus includes a return unit configured to return the monitoring signal received from the optical transmission apparatus and is configured to switch an output destination of the main signal received from the optical transmission apparatus to an optical transmission apparatus or the optical transmission apparatus. The optical transmission apparatus is configured to detect the monitoring signal returned from the return unit and notifies the optical transmission apparatus of a result of the detection. The optical transmission apparatus instructs the submarine branching apparatus to switch the output destination of the main signal in accordance with the notification.

An ONU includes a communication unit, an abnormal light emission prevention unit, and a control unit that transmits a data signal and a transmission permission signal to the communication unit and transmits the transmission permission signal to the abnormal light emission prevention unit between a transmission start time and a transmission end time. When the transmission permission signal is received, the communication unit, transmits an optical signal to an OLT, and transmits an operation signal to the abnormal light emission prevention unit during the transmission of the optical signal. The abnormal light emission prevention unit transmits a stop signal to the communication unit when a difference between a time for which the transmission permission signal is received and a time for which the operation signal is received is greater than or equal to a threshold value. The communication unit stops when the stop signal is received.

An ONU includes a communication unit, an abnormal light emission prevention unit, and a control unit that transmits a data signal and a transmission permission signal to the communication unit and transmits the transmission permission signal to the abnormal light emission prevention unit between a transmission start time and a transmission end time. When the transmission permission signal is received, the communication unit, transmits an optical signal to an OLT, and transmits an operation signal to the abnormal light emission prevention unit during the transmission of the optical signal. The abnormal light emission prevention unit transmits a stop signal to the communication unit when a difference between a time for which the transmission permission signal is received and a time for which the operation signal is received is greater than or equal to a threshold value. The communication unit stops when the stop signal is received.

A method for managing optical transceivers includes obtaining laser measurements for a laser operating in an optical transceiver in a network device, obtaining a failure profile for the laser, making a first determination that the laser measurements match the failure profile, and based on the first determination, initiating a remediation action for the optical transceiver.

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.