Abstract: An apparatus comprising an analog-to-digital converter (ADC); a frequency-domain equalizer (FDEQ); a time-domain interpolator positioned between the ADC and the FDEQ, wherein the time domain interpolator is coupled to the ADC and the FDEQ and configured to perform a time-domain interpolation to compensate a signal sample for a plurality of ADC induced changes.

Abstract: A digital apparatus comprising a fast Fourier transform (FFT) module configured to transform a time domain optical signal into a frequency domain optical signal, a circular shifter coupled to the FFT module and configured to provide coarse frequency offset compensation to the frequency domain optical signal based on an estimated frequency offset; and a frequency offset estimation module coupled to the circular shifter and configured to provide the estimated frequency offset based on a power spectrum of the frequency domain optical signal or a data block header autocorrelation of the time domain optical signal.

Abstract: An apparatus comprising a nonlinear lookup unit (NL-LUU) configured to add a phase shift to a signal sample to compensate for pattern dependent phase distortion, and one or more first phase adjustment units coupled to NL-LUU and configured to remove from the signal sample a nonlinear phase error from the NL-LUU, wherein the signal sample corresponds to a received signal polarization component of a polarization multiplexed (PM) coherent signal in a PM coherent optical system.

Abstract: An optical receiver comprising a frame detector configured to receive a polarized signal comprising a first bit stream and a second bit stream, and further configured to identify a plurality of frames in the first bit stream and the second bit stream using a composite header, and a time-domain equalizer (TDEQ) configured to separate the first bit stream and the second bit stream using a portion of the composite header.

Abstract: An apparatus comprising a plurality of receivers each configured to receive a plurality of polarized signals, a voltage control oscillator (VCO) coupled to the receivers and configured to control timing and sampling frequency of the polarized signals, and a signal processing component coupled to the receivers and configured to update a plurality of weighted linear factors, wherein the polarized signals and the weighted linear factors are used to obtain a combined signal, and wherein the weighted linear factors are updated using a real part or an imaginary part of the combined signal. Included is a method comprising using a linear factor to combine a plurality of polarized optical signals to provide time recovery information, and updating the linear factor using a combination of the polarized optical signals.

Abstract: A method comprising generating a plurality of first symbols that correspond to a side band pilot tone (SBPT) signal for a plurality of data streams, mapping the first symbols into a plurality of second symbols that correspond to a plurality of signal components of the polarization multiplexed (PM) optical signal, and transmitting the second symbols in a plurality of data blocks of a PM optical signal. An apparatus comprising at least one processor coupled to a memory and configured to obtain a data block that comprises a plurality of SBPTs in a received PM optical signal, estimate a set of values for a carrier frequency and a polarization state, update a tap weight of a master equalizer based on the estimated set of values, and update a plurality of slave equalizers based on the updated tap weight of the master equalizer.