Abstract: One example includes a frame synchronization module. The module includes a search correlator configured to find a first unique word (UW) pattern in a first set of digital sample blocks of a first data frame and a second UW pattern in a second digital sample blocks of a second data frame. The module also includes a buffer configured to store the first and second data frames and to concurrently release the buffered first and second data frames for downstream processing in response to time-aligning the first and second UW patterns of the respective first and second sets of digital sample blocks being aligned to a clock index.

Abstract: A system and method of estimating metric values from digital samples of received communications signal carrying symbols modulated in a selected first modulation format and symbols modulated in a second modulation format. The selected first modulation format can be selected from among multiple supported first modulation formats. The system can receive the digital samples in sample blocks a plurality of which constitute a data frame.

Abstract: One example includes an equalizer system. The system includes a filter system configured to receive digital sample blocks associated with an input signal and to provide equalized digital sample blocks associated with the respective digital sample blocks based on adaptive tap weights. Each of the digital sample blocks includes samples and each of the equalized digital sample blocks includes equalized samples. The system also includes a sample set selector to select a subset of equalized samples from each of the equalized digital sample blocks at the output of the filter and an error estimator configured to implement an error estimation algorithm on the subset of the equalized samples to determine a residual error associated with the equalized samples. The system further includes a tap weight generator configured to generate the adaptive tap weights in response to the residual error and to provide the adaptive tap weights to the filter.

Abstract: A system and method of estimating metric values from digital samples of received communications signal carrying symbols modulated in a selected first modulation format and symbols modulated in a second modulation format. The selected first modulation format can be selected from among multiple supported first modulation formats. The system can receive the digital samples in sample blocks a plurality of which constitute a data frame.

Abstract: One example includes an equalizer system. The system includes a filter system configured to receive digital sample blocks associated with an input signal and to provide equalized digital sample blocks associated with the respective digital sample blocks based on adaptive tap weights. Each of the digital sample blocks includes samples and each of the equalized digital sample blocks includes equalized samples. The system also includes a sample set selector to select a subset of equalized samples from each of the equalized digital sample blocks at the output of the filter and an error estimator configured to implement an error estimation algorithm on the subset of the equalized samples to determine a residual error associated with the equalized samples. The system further includes a tap weight generator configured to generate the adaptive tap weights in response to the residual error and to provide the adaptive tap weights to the filter.

Abstract: One example includes a frame synchronization module. The module includes a search correlator configured to find a first unique word (UW) pattern in a first set of digital sample blocks of a first data frame and a second UW pattern in a second digital sample blocks of a second data frame. The module also includes a buffer configured to store the first and second data frames and to concurrently release the buffered first and second data frames for downstream processing in response to time-aligning the first and second UW patterns of the respective first and second sets of digital sample blocks being aligned to a clock index.

Abstract: A system and method of estimating metric values from digital samples of received communications signal carrying symbols modulated in a selected first modulation format and symbols modulated in a second modulation format. The selected first modulation format can be selected from among multiple supported first modulation formats. The system can receive the digital samples in sample blocks a plurality of which constitute a data frame.

Abstract: A frame synchronization system and method is disclosed. The system can comprise controller, a search correlator, and a buffer. The controller can be configured to operate on a first stream of first digital sample blocks associated with a first signal and a second stream of second digital sample blocks associated with a second signal. The search correlator can be configured to determine an index of a first unique word (UW) pattern within first searchable digital sample blocks corresponding to the first digital sample blocks and an index of a second UW pattern within second searchable digital sample blocks corresponding to the second digital sample blocks. The buffer can be configured to store the first digital sample blocks and the second digital sample blocks and to release the buffered first and the second digital sample blocks for flow downstream when the stream of first digital sample blocks and the stream of second digital sample blocks are aligned.

Abstract: A system and method of estimating metric values from digital samples of received communications signal carrying symbols modulated in a selected first modulation format and symbols modulated in a second modulation format. The selected first modulation format can be selected from among multiple supported first modulation formats. The system can receive the digital samples in sample blocks a plurality of which constitute a data frame.

Abstract: A frame synchronization system and method is disclosed. The system can comprise controller, a search correlator, and a buffer. The controller can be configured to operate on a first stream of first digital sample blocks associated with a first signal and a second stream of second digital sample blocks associated with a second signal. The search correlator can be configured to determine an index of a first unique word (UW) pattern within first searchable digital sample blocks corresponding to the first digital sample blocks and an index of a second UW pattern within second searchable digital sample blocks corresponding to the second digital sample blocks. The buffer can be configured to store the first digital sample blocks and the second digital sample blocks and to release the buffered first and the second digital sample blocks for flow downstream when the stream of first digital sample blocks and the stream of second digital sample blocks are aligned.

Abstract: One example includes an equalizer system. The system includes a filter system configured to receive digital sample blocks associated with an input signal and to provide equalized digital sample blocks associated with the respective digital sample blocks based on adaptive tap weights. Each of the digital sample blocks includes samples and each of the equalized digital sample blocks includes equalized samples. The system also includes a sample set selector to select a subset of equalized samples from each of the equalized digital sample blocks at the output of the filter and an error estimator configured to implement an error estimation algorithm on the subset of the equalized samples to determine a residual error associated with the equalized samples. The system further includes a tap weight generator configured to generate the adaptive tap weights in response to the residual error and to provide the adaptive tap weights to the filter.

Abstract: Methods, systems, and devices are described for filtering data from an optical signal to compensate for chromatic dispersion in an optical path. Samples of different polarizations are filtered in the frequency domain with a matched filter by time-sharing a conversion module. The conversion module first converts a set of samples to the frequency domain for filtering when in a Fast Fourier Transform (FFT) configuration and then converts the filtered set of samples back to the time domain when in an Inverse FFT (IFFT) configuration. The size of the FFT in the FFT configuration and of the IFFT in the IFFT configuration is the same as the size of the samples being processed by the conversion module to enable both configurations to be based on a set of constant multipliers. Both configurations may be based on a pipelined architecture to sequentially process the samples in an efficient manner.

Abstract: Methods, systems, and devices are described for detecting and correcting a cycle slip occurrence in a coherent receiver. Unique words are used in each received frame to detect phase changes that indicate the occurrence of a cycle slip within a frame. The location of the cycle slip is identified based on measurements made within the frame. Those measurements include phase estimation measurements and reliability measurements. A phase of a portion of the frame subsequent to the identified location of the cycle slip is adjusted to correct for the cycle slip. By combining phase estimates of symbols from both vertical and horizontal polarizations, the location of the cycle slip may be more accurately determined because the measurement windows is less susceptible to thermal noise. The phase estimates are combined by adjusting a phase of the symbols of one polarization to match a phase of the symbols of the other polarization.

Abstract: Compensation for in-phase (I) and quadrature (Q) timing skew and offset in an optical signal may be achieved based on the correlation between derivatives of I and Q samples in the optical signal. The magnitude of the correlation between derivatives is measured to determine the presence of skew. Correlation between derivatives may be coupled with frequency offset information and/or with trials having additional positive and negative skew to determine presence of skew. Correlations are determined according to pre-defined time periods to provide for continued tracking and compensation for timing skew that may result from, for example, thermal drift.

Abstract: Compensation for in-phase (I) and quadrature (Q) timing skew and offset in an optical signal may be achieved based on the correlation between derivatives of I and Q samples in the optical signal. The magnitude of the correlation between derivatives is measured to determine the presence of skew. Correlation between derivatives may be coupled with frequency offset information and/or with trials having additional positive and negative skew to determine presence of skew. Correlations are determined according to pre-defined time periods to provide for continued tracking and compensation for timing skew that may result from, for example, thermal drift.

Abstract: Methods, systems, and devices are described for tap adjustment and reseeding in a digital filter. Filter and signal characteristics are measured and tap adjustments and reseeding of tap values may be performed based on the filter and signal characteristics. Filter characteristics that may be measured include a filter center of mass which may provide an indication that filter taps for a filter may be drifting toward a filter edge and thus reducing the dynamic range of the filter. Signal characteristics may include a timing offset between received input signals, and characteristics related to which of a particular input signal is present at a filter output. Filter taps, according to various embodiments, may be adjusted, and/or re-initialized responsive to one or more of the signal or filter characteristics.

Abstract: Compensation for in-phase (I) and quadrature (Q) timing skew and offset in an optical signal may be achieved based on the correlation between derivatives of I and Q samples in the optical signal. The magnitude of the correlation between derivatives is measured to determine the presence of skew. Correlation between derivatives may be coupled with frequency offset information and/or with trials having additional positive and negative skew to determine presence of skew. Correlations are determined according to pre-defined time periods to provide for continued tracking and compensation for timing skew that may result from, for example, thermal drift.

Abstract: Compensation for in-phase (I) and quadrature (Q) timing skew and offset in an optical signal may be achieved based on the correlation between derivatives of I and Q samples in the optical signal. The magnitude of the correlation between derivatives is measured to determine the presence of skew. Correlation between derivatives may be coupled with frequency offset information and/or with trials having additional positive and negative skew to determine presence of skew. Correlations are determined according to pre-defined time periods to provide for continued tracking and compensation for timing skew that may result from, for example, thermal drift.