Patent ID: 9413522
Filing Date: 2016-08-09
CPC Classification: H04B,H04L

Claim Text:
1. An optical receiver comprising: a receiving frontend to receive an optical signal and output an electric signal; a converter to convert the electric signal to a digital signal; an adaptive equalizer to adaptively equalize the digital signal; a synchronization part to synchronize a first polarized wave and a second polarized wave contained in the adaptively equalized digital signal with each other, polarization axes of the first polarized wave and the second polarized wave being perpendicular to each other; and a symbol offset determination part to determine an amount of symbol offset between the first polarized wave and the second polarized wave based upon symbol synchronization information of the first polarized wave and the second polarized wave supplied from the synchronization part, the symbol offset determination part being configured to repeat determination of the amount of the symbol offset and output a restart-up instruction to the adaptive equalizer until the symbol offset is minimized, wherein the symbol offset determination part changes an initial reference index for tap coefficients of the adaptive equalizer if the symbol offset does not become a first value or less after the restart-up instruction has been repeated a prescribed number of times, wherein if the determined symbol offset does not become the first value or less, then the symbol offset determination part determines whether the determined symbol offset is equal to a second value that is greater than the first value and counts an event of the second value if the determined symbol offset is equal to the second value, wherein when the initial reference index for the tap coefficients of the adaptive equalizer is changed, the symbol offset determination part stores a previous initial reference index together with a count value of the event of the second value, and wherein if the symbol offset does not become the first value or less even after the initial reference index for the tap coefficients has been changed within a prescribed range, the symbol offset determination part selects an index value that has a maximum count value of the event of the second value as the initial reference index.