Accurate calculation of polarization mode dispersion using blind equalization

A system comprising,

• an optical receiver configured to:
• receive a signal having a first component and a second component;
• perform equalization of the first component of the signal to create a first equalized signal,
• the equalization of the first component of the signal being based on a group of filter coefficients determined by a constant-modulus-algorithm (CMA);
• perform equalization of the second component of the signal to create a second equalized signal,
• the equalization of the second component the signal being based on the group of filter coefficients determined by the CMA;
• perform phase correction of the first equalized signal to create a first phase-corrected signal;
• perform phase correction of the second equalized signal to create a second phase-corrected signal;
• detect a first frame header pattern within the first phase-corrected signal,
• the first frame header pattern including a first frame header;
• detect a second frame header pattern within the second phase-corrected signal,
• the second frame header pattern including a second frame header;
• compute, based on the first frame header pattern and the second frame header pattern, a quantity of lock-in differential group delay (DGD) between the first phase-corrected signal and the second phase-corrected signal;
• and
• modify at least one filter coefficient, of the group of filter coefficients, based on the quantity of lock-in DGD,
• the at least one filter coefficient being adjusted to remove the quantity of lock-in DGD, and
• the at least one filter coefficient being modified to permit an amount of polarization mode dispersion to be accurately determined based on the group of filter coefficients.

A method, comprising:

• receiving, by a digital signal processor (DSP), a signal having a first component and a second component;
• equalizing, by the DSP, the first component of the signal to create a first equalized signal,
• the first component of the signal being equalized based on a first group of filter coefficients determined using a constant-modulus-algorithm (CMA);
• equalizing, by the DSP, the second component of the signal to create a second equalized signal,
• the second component of the signal being equalized based on a second group of filter coefficients determined using the CMA;
• performing, by the DSP, phase correction of the first equalized signal to create a first phase-corrected signal;
• performing, by the DSP, phase correction of the second equalized signal to create a second phase-corrected signal;
• identifying, by the DSP, a first header timing pattern included in the first phase-corrected signal,
• the first header timing pattern being based on a first frame header;
• identifying, by the DSP, a second header timing pattern included in the second phase-corrected signal,
• the second header timing pattern being based on a second frame header,
• the second frame header being different than the first frame header;
• determining, by the DSP, information associated with lock-in differential group delay (DGD) between the first phase-corrected signal and the second phase-corrected signal,
• the information associated with the lock-in DGD being determined based on the first frame header pattern relative to the second frame header pattern, and
• the information associated with the lock-in DGD including a quantity of lock-in DGD and a direction associated with the lock-in DGD;
• and
• adjusting, by the DSP, at least one filter coefficient based on the information associated with the lock-in DGD,
• the at least one filter coefficient being included in the first group of filter coefficients or the second group of filter coefficients.