Rapid polarization tracking in an optical channel

An apparatus comprising an optical data receiver for an intensity-modulated optical data signal intensity-modulated at a symbol rate, the optical data receiver comprising:

• an optical hybrid configured to mix the intensity-modulated optical data signal and an optical local-oscillator signal to generate first and second pluralities of mixed optical signals, the first plurality corresponding to a first polarization of the optical data signal, the second plurality corresponding to a different second polarization of the optical data signal;
• a first plurality of light detectors connected to generate first and second streams of digitalizations in response to the first plurality of mixed optical signals, the first and second streams of digitalizations providing measurements of different phase components of the first polarization of the optical data signal;
• a second plurality of light detectors connected to generate third and fourth streams of digitalizations in response to the second plurality of mixed optical signals, the third and fourth streams of digitalizations providing measurements of different phase components of the second polarization of the optical data signal;
• and
• a digital signal processor configured to:
• obtain time-resolved measurements of a state of polarization (SOP), with a finer time resolution than one over the symbol rate, of the intensity-modulated optical data signal based on the first, second, third, and fourth streams of digitalizations;
• compute, using a squaring circuit, a square of each received value of the first, second, third, and fourth streams of digitalizations;
• and
• generate a combination, using an adder, by summing the computed squares of the first, second, third, and fourth streams of digitalizations for each sampling time, to be proportional to optical power of the intensity-modulated optical data signal;
• and
• recover, using a carrier and data recovery circuit, data carried by the intensity-modulated optical data signal from the combination.