Abstract: Disclosed herein are methods and systems for optimizing an optical signal in an optical network having a leaf node with a coherent optical transceiver configured to receive an optical signal continuously transmitted at a first output power from a hub node over a link. The leaf node may be provided with signal quality correction circuitry configured to determine a signal quality of the optical signal and send the signal quality to a processor of the hub node. The processor of the hub node may be configured to compare the signal quality of the optical signal to a target signal quality margin, determine that the signal quality is outside the target signal quality margin, adjust the first output power of the optical signal to a second output power different than the first output power, and continuously transmit the optical signal at the second output power.

Abstract: Methods and systems for determining a receive signal quality of a new subcarrier group in an optical network, including a system in which each leaf node may report a current transmission output power to a hub node when it is determined that a receive signal quality of each of a plurality of subcarrier groups is within a required signal quality margin. A new leaf node may begin transmitting a new subcarrier group at a gradually increasing transmission output power until it reaches the required receive signal quality margin. The new leaf node gradually increases the transmission output power of the new subcarrier group until the hub node determines that any of the plurality of subcarrier groups and the new subcarrier group reached a maximum transmission output power or the signal quality of one or more of the plurality of subcarrier groups and the new subcarrier group begins to degrade.

Abstract: Disclosed herein are methods and systems for optimizing signal quality in an optical network having two or more hub nodes continuously outputting optical signals to a plurality of leaf nodes. Each of the plurality of leaf nodes may receive a combined optical signal from the hub nodes and determine an optical power and a signal quality of one optical subcarrier group and send a correction signal to the hub node that sent the subcarrier group. The hub nodes may send a power optimization request comprising the optical power and signal quality of each subcarrier group to a network controller. The network controller may use the optical power and signal quality to determine a power update for an optical power of the subcarrier group(s) and send the power update to the hub node transmitting the subcarrier group. The hub node may adjust the optical power based on the power update.

Abstract: Disclosed herein are methods and systems for optimizing an optical signal in an optical network having a hub node configured to receive an optical signal comprising a plurality of subcarrier groups each having a signal quality and a transmission output power, including a method that may comprise: determining, a first subcarrier group of the plurality of subcarrier groups with a lowest signal quality lower than a required signal quality margin; determining, a second subcarrier group of the plurality of subcarrier groups that has a highest transmission output power margin, Determining, that the transmission output power margin of the second subcarrier group is above a level needed to increase the lowest signal quality by a required signal quality increase; and sending signals to a first leaf node and a second leaf node causing the first leaf node to swap transmission positions of the first subcarrier group and the second subcarrier group.

Abstract: Methods and nodes including a hub node of a passive optical network (PON) comprising a DSP chain configured to: receive a signal burst from a leaf node in the PON, the signal burst having a frame comprising a payload and a frame header, the frame header comprising a clock-and-gain control section, a frame detection section, and an equalizer section; acquire a leaf node clock phase from the clock-and-gain control section of the frame header; estimate signal power of a signal burst from the leaf node in the PON; compensate for differences in the signal power of the signal burst from the leaf node; detect a Frame-Alignment-Sequence indicating arrival of the signal burst; determine MIMO polarization filter coefficients from the Frame-Alignment-Sequence; align a phase between X-Polarization and Y-Polarization of the signal burst using the MIMO polarization filter coefficients; and determine a local oscillator signal Frequency Offset Estimate (FOE).

Abstract: Disclosed herein are methods and systems for optimizing signal quality in an optical network having two or more hub nodes continuously outputting optical signals to a plurality of leaf nodes. Each of the plurality of leaf nodes may receive a combined optical signal from the hub nodes and determine an optical power and a signal quality of one optical subcarrier group and send a correction signal to the hub node that sent the subcarrier group. The hub nodes may send a power optimization request comprising the optical power and signal quality of each subcarrier group to a network controller. The network controller may use the optical power and signal quality to determine a power update for an optical power of the subcarrier group(s) and send the power update to the hub node transmitting the subcarrier group. The hub node may adjust the optical power based on the power update.

Abstract: Methods and systems for determining a receive signal quality of a new subcarrier group in an optical network, including a system in which each leaf node may report a current transmission output power to a hub node when it is determined that a receive signal quality of each of a plurality of subcarrier groups is within a required signal quality margin. A new leaf node may begin transmitting a new subcarrier group at a gradually increasing transmission output power until it reaches the required receive signal quality margin. The new leaf node gradually increases the transmission output power of the new subcarrier group until the hub node determines that any of the plurality of subcarrier groups and the new subcarrier group reached a maximum transmission output power or the signal quality of one or more of the plurality of subcarrier groups and the new subcarrier group begins to degrade.

Abstract: Disclosed herein are methods and systems for optimizing an optical signal in an optical network having a leaf node with a coherent optical transceiver configured to receive an optical signal continuously transmitted at a first output power from a hub node over a link. The leaf node may be provided with signal quality correction circuitry configured to determine a signal quality of the optical signal and send the signal quality to a processor of the hub node. The processor of the hub node may be configured to compare the signal quality of the optical signal to a target signal quality margin, determine that the signal quality is outside the target signal quality margin, adjust the first output power of the optical signal to a second output power different than the first output power, and continuously transmit the optical signal at the second output power.

Abstract: Disclosed herein are methods and systems for optimizing an optical signal in an optical network having a hub node configured to receive an optical signal comprising a plurality of subcarrier groups each having a signal quality and a transmission output power, including a method that may comprise: determining, a first subcarrier group of the plurality of subcarrier groups with a lowest signal quality lower than a required signal quality margin; determining, a second subcarrier group of the plurality of subcarrier groups that has a highest transmission output power margin, Determining, that the transmission output power margin of the second subcarrier group is above a level needed to increase the lowest signal quality by a required signal quality increase; and sending signals to a first leaf node and a second leaf node causing the first leaf node to swap transmission positions of the first subcarrier group and the second subcarrier group.

Abstract: An optical modulator comprises, as optical modulator components, first and second transmitter chains and a first optical time division multiplex, OTDM, generator arranged to receive time interleaved optical pulses generated by one of said optical modulator components.

Abstract: An approach for pre-distorting an input signal for an optical transmitter so as to at least partially compensate in advance for linear and non-linear distortions of the optical transmitter is provided.

Abstract: An optical modulator comprises, as optical modulator components, first and second transmitter chains and a first optical time division multiplex, OTDM, generator arranged to receive time interleaved optical pulses generated by one of said optical modulator components.

Abstract: An approach for pre-distorting an input signal for an optical transmitter so as to at least partially compensate in advance for linear and non-linear distortions of the optical transmitter is provided.

Abstract: A self-calibration procedure for an optical transmitter is provided. During the self-calibration procedure, a phase bias of an optical modulator of the optical transmitter is set so that an in-phase path and a quadrature path of the optical modulator are in phase. Stimulus signals are supplied to the in-phase and quadrature paths of the optical modulator, over a frequency range. Detection, with a photodetector, is made of an optical output of the optical modulator at a plurality of frequency steps over the frequency range. A photodetector converts an optical output of the optical modulator to an electrical signal. First and second measurement values are generated from the electrical signal output from the photodetector. A frequency spectrum and/or time delay is computed from the first and second measurement values for each frequency step value over the frequency range.

Abstract: A system includes a laser configured to generate a tunable optical frequency. The system also includes an optical transmitter to map baseband data to symbols represented in a digital modulation constellation, add a frequency offset to the digital modulation constellation to cause the digital modulation constellation to rotate at a rate equal to the added frequency offset, modulate the optical frequency with the rotating digital modulation constellation, and transmit the resulting modulated optical frequency. The system also includes an optical receiver to receive the transmitted modulated optical frequency and, using the tunable optical frequency, detect the rotating digital modulation constellation conveyed by the received modulated optical frequency.

Abstract: Embodiments of the present disclosure provide techniques and an apparatus for partitioning calibration data into line card and pluggable properties and processing the partitioned data using a processor of the line card. For example, calibration information corresponding to components in the pluggable module may be stored on the pluggable module and transferred from the pluggable optical module to the processor on the line card. The processor may combine the calibration information received from the optical module with calibration information corresponding to properties on the line card to obtain system calibration information. The system calibration information may be used to configure one or more components used to process electric signals sent to or received from the optical module.

Abstract: A system includes a laser configured to generate a tunable optical frequency. The system also includes an optical transmitter to map baseband data to symbols represented in a digital modulation constellation, add a frequency offset to the digital modulation constellation to cause the digital modulation constellation to rotate at a rate equal to the added frequency offset, modulate the optical frequency with the rotating digital modulation constellation, and transmit the resulting modulated optical frequency. The system also includes an optical receiver to receive the transmitted modulated optical frequency and, using the tunable optical frequency, detect the rotating digital modulation constellation conveyed by the received modulated optical frequency.

Abstract: In an optical receiver, an optical local oscillator (LO) frequency is generated. A modulated optical frequency is received at the optical receiver. An LO-signal frequency offset between the received modulated optical frequency and the optical LO frequency is determined. A determination is made as to whether the LO-signal frequency offset is in one of multiple predefined non-overlapping target windows that cover respective non-zero LO-signal frequency offsets. If it is determined that the LO-signal frequency offset is not in one of the target windows, the optical LO frequency is tuned to drive the LO-signal frequency offset toward one of the target windows to ensure the LO-signal frequency offset is non-zero.

Abstract: Embodiments of the present disclosure provide techniques and an apparatus for partitioning calibration data into line card and pluggable properties and processing the partitioned data using a processor of the line card. For example, calibration information corresponding to components in the pluggable module may be stored on the pluggable module and transferred from the pluggable optical module to the processor on the line card. The processor may combine the calibration information received from the optical module with calibration information corresponding to properties on the line card to obtain system calibration information. The system calibration information may be used to configure one or more components used to process electric signals sent to or received from the optical module.

Abstract: An optical signal is received at a coherent optical receiver. The received optical signal is converted to a first electrical signal and a second electrical signal through a first photodetector and a second photodetector, respectively. The first electrical signal is input into a first single input variable gain amplifier, and the second electrical signal is input into a second single input variable gain amplifier. A gain of at least one of the first single input variable gain amplifier or the second single input variable gain amplifier is controlled to balance the output of the first single input variable gain amplifier and the output of the second single input variable gain amplifier. The output of the first single input variable gain amplifier and the output of the second single input variable gain amplifier are input into a differential amplifier. A receiver output is obtained at an output of the differential amplifier.