Feed-forward carrier phase recovery for optical communications

An apparatus for carrier phase recovery of a carrier wave modulated with a plurality of information symbols, the apparatus comprising:

• a processor;
• and
• a memory to store computer program instructions,
• the computer program instructions, when executed on the processor, cause the processor to perform operations comprising:
• receiving a digital signal corresponding to an information symbol, wherein the information symbol represents data;
• and
• performing a coarse phase recovery using the digital signal, wherein performing the coarse phase recovery comprises:
• generating a first estimate of an optimal phase angle corresponding to the digital signal by performing a coarse blind phase search;
• generating a second estimate of the optimal phase angle corresponding to the digital signal by inputting the digital signal and the first estimate of the optimal phase angle into a first maximum likelihood phase recovery and decoding block;
• and
• generating a third estimate of the optimal phase angle corresponding to the digital signal by inputting the digital signal and the second estimate of the optimal phase angle into a second maximum likelihood phase recovery and decoding block.

A non-transitory computer readable medium storing computer program instructions for carrier phase recovery of a carrier wave modulated with a plurality of information symbols, which, when executed on a processor, cause the processor to perform operations comprising:

• receiving a digital signal corresponding to an information symbol, wherein the information symbol represents data;
• and
• performing a coarse phase recovery using the digital signal, wherein the performing the coarse phase recovery comprises:
• generating a first estimate of an optimal phase angle corresponding to the digital signal by performing a coarse blind phase search;
• generating a second estimate of the optimal phase angle corresponding to the digital signal by inputting the digital signal and the first estimate of the optimal phase angle into a first maximum likelihood phase recovery and decoding block;
• and
• generating a third estimate of the optimal phase angle corresponding to the digital signal by inputting the digital signal and the second estimate of the optimal phase angle into a second maximum likelihood phase recovery and decoding block.