Adaptive equalizer tap coefficient correction method and optical receiver

An optical receiver, comprising:

• a receiver configured to receive an optical signal and output an electric signal;
• a converter configured to convert the electric signal into a digital signal;
• an adaptive equalizer configured to adaptively equalize the digital signal;
• a monitor configured to monitor a symbol synchronization time of a first polarization included in the digital signal that has been adaptively equalized and a symbol synchronization time of a second polarization orthogonal to the first polarization;
• and
• a tap coefficient controller connected to the adaptive equalizer and the monitor and configured to control tap coefficients set in the adaptive equalizer,
• wherein the tap coefficient controller configured to:
• obtain a synchronization symbol difference between the first polarization and the second polarization, based on an output of the monitor,
• obtain a delay amount of the first polarization and the second polarization in the adaptive equalizer,
• calculate, based on the synchronization symbol difference and the delay amount, a correction reference gravity center of the tap coefficients set in the adaptive equalizer where a horizontal axis represents a tap number and a vertical axis represents a tap coefficient and a tap number or a nearest tap number with which an area of a drawn figure is halved is set as a gravity center of tap coefficients, and
• perform a correction of shifting the entire tap coefficients in units of symbol to cause the correction reference gravity center to be closest to a tap center.