Reset in a receiver using center of gravity of equalizer coefficients
View Patent ↗A receiver applies a calibration method to compensate for skew between input channels. The receiver skew is estimated by observing the coefficients of an adaptive equalizer which adjusts the coefficients based on time-varying properties of the multi-channel input signal. The receiver skew is compensated by programming the phase of the sampling clocks for the different channels. Furthermore, during real-time operation of the receiver, channel diagnostics is performed to automatically estimate differential group delay and/or other channel characteristics based on the equalizer coefficients using a frequency averaging or polarization averaging approach. Framer information can furthermore be utilized to estimate differential group delay that is an integer multiple of the symbol rate. Additionally, a DSP reset may be performed when substantial signal degradation is detected based on the channel diagnostics information.
1. A method for operating a digital signal processor, comprising:
receiving a digital input vector;
equalizing the digital signal vector using an adaptive equalizer to generate an equalized signal vector, the adaptive equalizer adaptively updating equalizer coefficients based on characteristics of the digital signal vector;
determining a first center of gravity for equalizer coefficients corresponding to first channels of the digital input vector having a first polarization;
comparing the first center of gravity to a first predefined range for the first center of gravity; and
resetting the digital signal processor responsive to the first center of gravity falling outside the predefined range for the first center of gravity.
2. The method of claim 1 , wherein the first polarization comprises a horizontal polarization.
3. The method of claim 1 , wherein the first polarization comprises a vertical polarization.
4. The method of claim 1 , further comprising:
determining a second center of gravity for equalizer coefficients corresponding to second channels of the digital input vector having a second polarization different than the first polarization;
comparing the second center of gravity to a second predefined range for the second center of gravity; and
resetting the digital signal processor responsive to the second center of gravity falling outside the second predefined range for the second center of gravity.
5. A method for operating a digital signal processor, comprising:
receiving a digital input vector;
equalizing the digital signal vector using an adaptive equalizer to generate an equalized signal vector, the adaptive equalizer to adaptively update equalizer coefficients based on characteristics of the digital signal vector;
determining a horizontal center of gravity for equalizer coefficients corresponding to horizontally polarized channels of the digital input vector;
comparing the horizontal center of gravity to a predefined range for the horizontal center of gravity;
determining a vertical center of gravity for equalizer coefficients corresponding to vertically polarized channels of the digital input vector;
comparing the vertical center of gravity to a predefined range for the vertical center of gravity; and
resetting the digital signal processor responsive to both of: (1) the horizontal center of gravity falling outside the predefined range for the horizontal center of gravity, and (2) the vertical center of gravity falling outside the predefined range for the vertical center of gravity.
6. The method of claim 1 , further comprising:
responsive to the first center of gravity falling within the predefined range at an initial time point, re-evaluating the first center of gravity at a subsequent time point and determining whether or not to reset the digital signal processor based on the re-evaluation.
7. The method of claim 1 , further comprising:
responsive to the first center of gravity falling within the predefined range, discontinuing further evaluations of the first center of gravity.
8. The method of claim 1 , wherein resetting the digital signal processor causes the digital signal processor to restart an adaptive algorithm performed by the digital signal processor using different initial conditions.
9. A system for an optical communication system, comprising:
a digital signal processor; and
a non-transitory computer readable storage medium storing computer-executable instructions, the instructions when executed causing the digital signal processor to perform steps including:
receiving a digital input vector;
equalizing the digital signal vector using an adaptive equalizer to generate an equalized signal vector, the adaptive equalizer adaptively updating equalizer coefficients based on characteristics of the digital signal vector;
determining a first center of gravity for equalizer coefficients corresponding to first channels of the digital input vector having a first polarization;
comparing the first center of gravity to a first predefined range for the first center of gravity; and
resetting the digital signal processor responsive to the first center of gravity falling outside the predefined range for the first center of gravity.
10. The system of claim 9 , wherein the first polarization comprises a horizontal polarization.
11. The system of claim 9 , wherein the first polarization comprises a vertical polarization.
12. The system of claim 9 , further comprising:
determining a second center of gravity for equalizer coefficients corresponding to second channels of the digital input vector having a second polarization different than the first polarization;
comparing the second center of gravity to a second predefined range for the second center of gravity; and
resetting the digital signal processor responsive to the second center of gravity falling outside the second predefined range for the second center of gravity.
13. A system for an optical communication system, comprising:
a digital signal processor; and
a non-transitory computer readable storage medium storing computer-executable instructions, the instructions when executed causing the digital signal processor to perform steps including:
determining a horizontal center of gravity for equalizer coefficients corresponding to horizontally polarized channels of the digital input vector;
comparing the horizontal center of gravity to a predefined range for the horizontal center of gravity;
determining a vertical center of gravity for equalizer coefficients corresponding to vertically polarized channels of the digital input vector;
comparing the vertical center of gravity to a predefined range for the vertical center of gravity; and
resetting the digital signal processor responsive to both of: (1) the horizontal center of gravity falling outside the predefined range for the horizontal center of gravity, and (2) the vertical center of gravity falling outside the predefined range for the vertical center of gravity.
14. The system of claim 9 , wherein the computer-executable instructions further cause the digital signal processor to perform steps including:
responsive to the first center of gravity falling within the predefined range at an initial time point, re-evaluating the first center of gravity at a subsequent time point and determining whether or not to reset the digital signal processor based on the re-evaluation.
15. The system of claim 9 , wherein the computer-executable instructions further cause the digital signal processor to perform steps including:
responsive to the first center of gravity falling within the predefined range, discontinuing further evaluations of the first center of gravity.
16. The system of claim 9 , wherein resetting the digital signal processor causes the digital signal processor to restart an adaptive algorithm performed by the digital signal processor using different initial conditions.