Systems and methods for carrier phase recovery

A data frame structuring unit for a transmitter in an optical communication system, the data frame structuring unit comprising:

• an input portion configured to receive a first optical carrier having a first polarization and a second optical carrier having a second polarization different from the first polarization;
• a data unit generator configured to generate a first generated data unit having a data frame structure designed for each of the first and second optical carriers;
• a modulator configured to modulate (i) a first component of the generated data unit onto the first optical carrier, and (ii) a second component of the generated data unit onto the second optical carrier during a same first time slot corresponding to the modulated first component;
• and
• an output portion configured to output the modulated first and second optical carriers as a dual-polarization multiplexed signal over an optical fiber medium in operable communication with the transmitter,
• wherein the first component of the first generated data unit comprises has a length of N symbols,
• wherein N is a number greater than zero,
• wherein each symbol of the N symbols includes two or more digital bits, and
• wherein the second component of the first generated data unit comprises entirely null bits within a complete duration of the first component in the same time slot.

A data frame structuring unit for a transmitter in an optical communication system, the data frame structuring unit comprising:

• an input portion configured to receive a first optical carrier having a first polarization and a second optical carrier having a second polarization different from the first polarization;
• a data unit generator configured to generate a first generated data unit having a data frame structure designed for each of the first and second optical carriers;
• a modulator configured to modulate (i) a first component of the generated data unit onto the first optical carrier, and (ii) a second component of the generated data unit onto the second optical carrier during a same first time slot corresponding to the modulated first component;
• and
• an output portion configured to output the modulated first and second optical carriers as a dual-polarization multiplexed signal over an optical fiber medium in operable communication with the transmitter,
• wherein the first component of the first generated data unit comprises N-symbol length data, N being a number greater than zero,
• wherein the second component of the first generated data unit comprises null bits within a duration of the first component in the same time slot,
• wherein the modulator is further configured to modulate (i) the first component onto the first optical carrier preceding a first payload portion of the first optical carrier in time, and (ii) the second component onto the second optical carrier preceding a second payload portion of the second optical carrier in time,
• wherein the data unit generator is further configured to generate a second generated data unit for the first and second optical carriers, wherein the second generated data unit comprises a third component for the first optical carrier, and a fourth component for the second optical carrier and
• wherein the modulator is further configured to modulate the second generated data unit onto the first and second optical carriers such that (i) the third component is disposed between the first component and the first payload portion of the first optical carrier in time, and (ii) fourth component is disposed between the second component and the second payload portion of the second optical carrier in time.

A polarization-diversity coherent receiver for a coherent optical communication system, the receiver comprising:

• an input portion configured to receive a first polarization of a dual-polarization multiplexed signal and a second polarization the dual-polarization multiplexed signal different from the first polarization;
• a state-of-polarization (SoP) estimation unit in communication with the input portion and configured to detect a first designated data unit from the first polarization and a second designated data unit from the second polarization and calculate an inverse matrix based on the detected first and second designated data units;
• a first adaptive equalizer configured to receive the first polarization and the calculated inverse matrix, apply a first filter coefficient, and output a first equalized signal for the first polarization;
• a second adaptive equalizer configured to receive the second polarization and the calculated inverse matrix, apply a second filter coefficient, and output a second equalized signal for the second polarization;
• and
• an error function unit configured to update (i) at least one tap of the first adaptive equalizer based on the output first equalized signal, and (ii) at least one tap of the second adaptive equalizer based on the output second equalized signal.