Abstract: Carrier phase estimation techniques are provided for processing a received optical signal having a carrier modulated according to a modulation scheme. First and second carrier phase estimation operations are performed on a digital signal derived from an optical carrier obtained from the received optical signal using coherent optical reception. The first carrier phase estimation operation tracks relatively fast phase variations of the optical carrier of the received optical signal to produce a first carrier phase estimation and the second carrier phase estimation operation tracks relatively slow phase variations of the optical carrier of the received optical signal to produce a second carrier phase estimation. A difference between the first and second carrier phase estimations is computed. Occurrence of a cycle slip is determined when the difference is greater than a threshold. A correction is applied to the first carrier phase estimation when the low pass filtered difference exceeds the threshold.

Abstract: According to a first aspect, techniques are provided to optimize a Mach-Zehnder modulator drive waveform by distorting the outer modulation levels of the waveform, thereby equalizing eye openings of the received optical field, and in particular creating a wider and more defined central eye opening of the received optical field. According to a second aspect, techniques are provided to adjust in-phase (I) modulation levels based on the imperfect performance of a Mach-Zehnder modulator allocated to modulate quadrature-phase (Q) modulation levels, and conversely to adjust the Q modulation levels based on the imperfect performance of an MZ modulator allocated to modulate I modulation levels.

Abstract: Techniques are provided for estimation of the chromatic dispersion (CD) in an optical signal received by an optical receiver. The techniques involve iteratively adjusting dispersion compensation coefficients of one or more filters configured to compensate for the CD in the received optical signal. At each iteration of the dispersion compensation coefficient adjustment, electrical domain signals are filtered to generate digitally-filtered signals. The electrical domain signals are generated based on the received optical signal. Also at each iteration of the dispersion compensation coefficient adjustment, an amplitude histogram of the digitally-filtered signals is generated. The amplitude histograms generated at each iteration are evaluated to generate an estimate of the chromatic dispersion in the received optical signal.