Abstract: Optical fiber data communications are described. A controller can determine chromatic dispersion of an optical signal that is to be demodulated using coherent detection. The controller can then determine the chromatic dispersion of another optical signal that is to be demodulated using direct detection. The chromatic dispersion of the other optical signal can then be adjusted to account for chromatic dispersion experienced by the other optical signal when it propagated through an optical fiber.

Abstract: The present invention is directed to a communication signal tracking system comprising an optical receiver including one or more delay line interferometers (DLIs) configured to demultiplex incoming optical signals and a transimpedance amplifier configured to convert the incoming optical signals to incoming electrical signals. The communication signal tracking system further includes a control module configured to calculate a bit-error-rate (BER) of the incoming electrical signals before forward-error correction decoding, and use the BER as a parameter for optimizing settings of the one or more DLIs in one or more iterations in a control loop and generating a back-channel data.

Abstract: Optical fiber data communications are described. An error correction circuit can receive a signal and correct bit errors of that signal. The circuit can then determine characteristics of the signal (e.g., its bit error rate (BER)) and adjust the operations performed to correct the bit errors of the signal based on the characteristics.

Abstract: Optical fiber data communications are described. A controller can determine chromatic dispersion of an optical signal that is to be demodulated using coherent detection. The controller can then determine the chromatic dispersion of another optical signal that is to be demodulated using direct detection. The chromatic dispersion of the other optical signal can then be adjusted to account for chromatic dispersion experienced by the other optical signal when it propagated through an optical fiber.

Abstract: An example embodiment includes optical receiver that includes a polarization beam splitter (PBS), a polarization controller, and a forward error correction (FEC). The PBS is configured to split a received optical signal having an unknown polarization state into two orthogonal polarizations (x?-polarization and y?-polarization). The polarization controller includes no more than two couplers and no more than two phase shifters per wavelength channel of the x?-polarization and the y?-polarization. The polarization controller is configured to demultiplex the x?-polarization and the y?-polarization into a first demultiplexed signal having an first polarization on which a data signal is modulated and a second demultiplexed signal having a second, orthogonal polarization on which a pilot carrier oscillator signal is encoded. The FEC decoder module is configured to correct a burst of errors resulting from resetting one of the phase shifters based on error correction code (ECC) data encoded in the data signal.

Abstract: The present invention is directed to a communication signal tracking system comprising an optical receiver including one or more delay line interferometers (DLIs) configured to demultiplex incoming optical signals and a transimpedance amplifier configured to convert the incoming optical signals to incoming electrical signals. The communication signal tracking system further includes a control module configured to calculate a bit-error-rate (BER) of the incoming electrical signals before forward-error correction decoding, and use the BER as a parameter for optimizing settings of the one or more DLIs in one or more iterations in a control loop and generating a back-channel data.

Abstract: An example embodiment includes optical receiver that includes a polarization beam splitter (PBS), a polarization controller, and a forward error correction (FEC). The PBS is configured to split a received optical signal having an unknown polarization state into two orthogonal polarizations (x?-polarization and y?-polarization). The polarization controller includes no more than two couplers and no more than two phase shifters per wavelength channel of the x?-polarization and the y?-polarization. The polarization controller is configured to demultiplex the x?-polarization and the y?-polarization into a first demultiplexed signal having an first polarization on which a data signal is modulated and a second demultiplexed signal having a second, orthogonal polarization on which a pilot carrier oscillator signal is encoded. The FEC decoder module is configured to correct a burst of errors resulting from resetting one of the phase shifters based on error correction code (ECC) data encoded in the data signal.

Abstract: A multi-channel receiver that includes a first clock recovery unit configured to recover a first clock signal associated with a first optical channel is disclosed. A first coefficient estimation unit estimates a first set of coefficients using the first clock signal. A second clock recovery unit configured to recover a second clock signal associated with a second optical channel using the first clock signal as a reference clock signal. A second coefficient estimation unit estimates a second set of coefficients using the first set of coefficients.

Abstract: A data communication system for transmitting packets over one or more optical fibers includes a transponder with a number of digital signal processors that transmit data packets on different optical channels. The transponder includes a switch that receives a data packet on an input and selects one of the digital signal processors to transmit the packet based on quality metrics for the different optical channels and/or information included in an OSI header for the data packet.

Abstract: Optical fiber data communications are described. A comb laser can provide light at a first wavelength and a second wavelength. Using that light, polarization multiplexing circuitry can generate an optical signal having different polarization components and transceivers can transmit the optical signal having the first wavelength and a probe having the second wavelength via an optical fiber. A polarimeter can determine characteristics of the polarization of the probe. Based on the characteristics, a polarization controller can adjust a polarization of the optical signal. The optical signal can then be split into different polarization components.

Abstract: Optical fiber data communications are described. A comb laser can provide light at a first wavelength and a second wavelength. Using that light, polarization multiplexing circuitry can generate an optical signal having different polarization components and transceivers can transmit the optical signal having the first wavelength and a probe having the second wavelength via an optical fiber. A polarimeter can determine characteristics of the polarization of the probe. Based on the characteristics, a polarization controller can adjust a polarization of the optical signal. The optical signal can then be split into different polarization components.

Abstract: A multi-channel receiver that includes a first clock recovery unit configured to recover a first clock signal associated with a first optical channel is disclosed. A first coefficient estimation unit estimates a first set of coefficients using the first clock signal. A second clock recovery unit configured to recover a second clock signal associated with a second optical channel using the first clock signal as a reference clock signal. A second coefficient estimation unit estimates a second set of coefficients using the first set of coefficients.

Abstract: A data communication system for transmitting packets over one or more optical fibers includes a transponder with a number of digital signal processors that transmit data packets on different optical channels. The transponder includes a switch that receives a data packet on an input and selects one of the digital signal processors to transmit the packet based on quality metrics for the different optical channels and/or information included in an OSI header for the data packet.

Abstract: A method of transmitting data may include receiving feedback information that includes effective channel bandwidths, signal-to-noise ratios (SNRs) associated with multiple optical channels on an optical link, and individual SNRs associated with subcarriers on each optical channel. The method may include determining multiple subcarrier power allocation schemes based on the feedback information. Each subcarrier power allocation scheme may be associated with a corresponding optical channel from the multiple optical channels and may be configured to allocate a signal power among subcarriers configured to transmit on the corresponding optical channel. The method may include determining, based on the feedback information, an optical power allocation scheme configured to allocate an optical power among the multiple optical channels. The method may include transmitting data on the multiple optical channels based on the multiple subcarrier power allocation schemes and the optical power allocation scheme.

Abstract: A method of blind tap coefficient adaptation includes receiving a digital data signal including random digital data, equalizing a first portion of the digital data signal using a first set of predetermined tap coefficients and a second portion of the digital data signal using a second set of predetermined tap coefficients. The method includes generating a first eye diagram and a second eye diagram from a first portion and a second portion of an equalized signal, respectively. The first eye diagram is compared with the second eye diagram to determine which of the sets of predetermined tap coefficients results in a data signal having a higher signal quality. The method includes inputting to an equalizer as an initial set of tap coefficients the first set of predetermined tap coefficients or the second set of predetermined tap coefficients according to the determination.

Abstract: A method of performing clock recovery and equalizer coefficient estimation in a multi-channel receiver may include recovering, at a first clock recovery unit, a first clock signal associated with a first channel. The method may include estimating a first set of coefficients for a first equalizer associated with the first channel using the first clock signal. The method may include passing the first clock signal to a second clock recovery unit associated with a second channel. The method may also include recovering, at the second clock recovery unit, a second clock signal associated with the second channel using the first clock signal as a reference clock signal. The method may also include passing the first set of coefficients as initialization coefficients to a second equalizer associated with the second channel. The method may also include estimating a second set of coefficients for the second equalizer using the initialization coefficients.

Abstract: An example embodiment includes optical receiver that includes a polarization beam splitter (PBS), a polarization controller, and a forward error correction (FEC). The PBS is configured to split a received optical signal having an unknown polarization state into two orthogonal polarizations (x?-polarization and y?-polarization). The polarization controller includes no more than two couplers and no more than two phase shifters per wavelength channel of the x?-polarization and the y?-polarization. The polarization controller is configured to demultiplex the x?-polarization and the y?-polarization into a first demultiplexed signal having an first polarization on which a data signal is modulated and a second demultiplexed signal having a second, orthogonal polarization on which a pilot carrier oscillator signal is encoded. The FEC decoder module is configured to correct a burst of errors resulting from resetting one of the phase shifters based on error correction code (ECC) data encoded in the data signal.

Abstract: A method of performing clock recovery and equalizer coefficient estimation in a multi-channel receiver may include recovering, at a first clock recovery unit, a first clock signal associated with a first channel. The method may include estimating a first set of coefficients for a first equalizer associated with the first channel using the first clock signal. The method may include passing the first clock signal to a second clock recovery unit associated with a second channel. The method may also include recovering, at the second clock recovery unit, a second clock signal associated with the second channel using the first clock signal as a reference clock signal. The method may also include passing the first set of coefficients as initialization coefficients to a second equalizer associated with the second channel. The method may also include estimating a second set of coefficients for the second equalizer using the initialization coefficients.

Abstract: A method of transmitting data may include converting a stream of serial data bits into a set of parallel quadrature amplitude modulation (QAM) symbols. The method may additionally include applying a partial discrete Fourier transform-spread technique to transform a block of low-frequency subcarriers into a single-carrier QAM signal. The single-carrier QAM signal may bear information of a first subset of QAM symbols from the set of parallel QAM symbols. The method may additionally include transforming one or more remaining QAM symbols to form one or more subcarriers. Each of the one or more subcarriers may bear information of a corresponding QAM symbol from the one or more remaining QAM symbols. The method may additionally include generating a hybrid signal that includes the single-carrier QAM signal and the one or more subcarriers. The method may additionally include transmitting the hybrid signal.

Abstract: An example embodiment includes optical receiver that includes a polarization beam splitter (PBS), a polarization controller, and a forward error correction (FEC). The PBS is configured to split a received optical signal having an unknown polarization state into two orthogonal polarizations (x?-polarization and y?-polarization). The polarization controller includes no more than two couplers and no more than two phase shifters per wavelength channel of the x?-polarization and the y?-polarization. The polarization controller is configured to demultiplex the x?-polarization and the y?-polarization into a first demultiplexed signal having an first polarization on which a data signal is modulated and a second demultiplexed signal having a second, orthogonal polarization on which a pilot carrier oscillator signal is encoded. The FEC decoder module is configured to correct a burst of errors resulting from resetting one of the phase shifters based on error correction code (ECC) data encoded in the data signal.