Patent ID: 7817925

Claim:
A dispersion compensation control apparatus for receiving an optical signal with a predetermined frequency, which is phase-modulated light applied with intensity modulation slower in the modulation speed than the phase modulation with a predetermined frequency, comprising: a variable dispersion compensation unit, which can vary an amount of dispersion compensation, to perform dispersion compensation of the optical signal; a clock recovery unit to extract an intensity modulation component from the received optical signal and to recover a clock from the extracted intensity modulation component; a comparator to compare a frequency of the recovered clock with the predetermined frequency; a demodulator to demodulate the phase modulated optical signal; an error rate calculation unit to calculate an error rate of a demodulation result; and a dispersion compensation amount controller, based on the comparison result, to control an amount of dispersion compensation of the variable dispersion compensation unit so that the difference in the frequency of the clock becomes small, and, after completion of reducing the difference in the frequency of the clock, to control an amount of dispersion compensation of the variable dispersion compensation unit so that the error rate becomes small.