Patent ID: 8463133

Claim:
In a coherent optical receiver of an optical communications system, a method of estimating a location of a periodic SYNC burst within an optical signal received through the optical communications system, the method comprising steps of: calculating a cross-correlation between a multi-bit digital signal corresponding to the optical signal received through the optical communications system and a known pattern corresponding to the SYNC burst; logically dividing the cross-correlation into at least one sub-block, each sub-block comprising a plurality of contiguous samples of the cross-correlation spanning less than a SYNC burst period and having a repetition rate that is synchronous with the digital signal; processing each sub-block to identify a candidate sub-block within which the SYNC burst is most likely located; and processing samples of the cross-correlation within the candidate sub-block to identify the most likely location of the SYNC burst; wherein the steps of calculating the cross-correlation, processing each sub-block and processing samples of the cross-correlation within the candidate sub-block to identify the most likely location of the SYNC burst are performed before detection of symbols modulated on the received optical signal.