1. A signal equalizer for compensating impairments of an optical signal received through a link of a high speed optical communications network, the signal equalizer comprising: means for computing at least one set of compensation vectors for compensating at a first type of impairments; an update block for computing a set of compensation coefficients for compensating a second type of impairments; and a frequency domain processor coupled to receive respective raw multi-bit in-phase (I) and quadrature (Q) sample streams of each received polarization of the optical signal, the frequency domain processor including means being configured to process the multi-bit sample streams using the compensation vectors and the compensation coefficients, in the frequency domain, to generate multi-bit estimates of symbols modulated onto each transmitted polarization of the optical signal; wherein a recalculation rate of the compensation coefficients is greater than that of the compensation vectors.