Data synchronization in optical networks and devices

An apparatus comprising:

• a receiver operable to receive an optical signal including frames of data symbols, the receiver comprising:
• a local oscillator laser operable to supply a local oscillator signal;
• an optical hybrid circuit operable to receive polarization components of the optical signal and the local oscillator signal, and to supply mixing products;
• a photodiode circuit operable to receive the mixing products and output an electrical signal based on the optical signal;
• and
• processor circuitry operable to:
• determine estimated positions of framer indices in the frames of data symbols;
• identify, using a non-linear filter, a subset of estimated positions of the determined estimated positions of the framer indices that are greater than a threshold distance away from a median index position of the determined estimated positions of the framer indices;
• generate a second subset of estimated positions by removing the subset of estimated positions from the determined estimated positions across the frames of data symbols;
• and
• determine an estimated framer index position of the frames of data symbols by determining an average position of the second subset of estimated positions.

A receiver comprising:

• receiver circuitry operable to receive frames and provide digital samples of the frames, each of the frames comprising a frame header having framer symbols and payload data having payload symbols;
• and
• processor circuitry coupled to the receiver circuit and operable to:
• obtain the digitized samples of the frames from the receiver circuit;
• for each frame:
• deinterleave a portion of the frame to separate a first set of symbols from a second set of symbols included in the frame;
• generate a third set of symbols by mixing the first set of symbols with a fourth set of symbols;
• determine a cross correlation of the third set of symbols and the second set of symbols;
• and
• determine an estimated position of the frame header by identifying a peak value associated with the cross correlation of the third set of symbols and the second set of symbols;
• for a plurality of the frames obtained from the receiver circuit:
• identify, using a non-linear filter, a subset of estimated positions of the frame headers that are greater than a threshold distance away from a median index position of the determined estimated positions of the frame headers;
• generate a second subset of estimated positions by removing the subset of estimated positions from the determined estimated positions for the frames;
• and
• determine an estimated position of the frame headers by determining an average position of the frame headers in the second subset of estimated positions.