OPTICAL MODULATION DEVICE AND OPTICAL TRANSMITTER, AND CONTROL METHOD OF OPTICAL MODULATION DEVICE

摘要

PROBLEM TO BE SOLVED: To provide a control technique for monitoring a phase shift between signals used for driving optical modulators connected forward or backward including the direction of the phase shift without giving influence on transmission characteristics in an optical modulation device of a multiplex modulation system.SOLUTION: The optical modulation device uses, as monitor light, a portion of signal light multiplex-modulated by first and second optical modulation parts, extracts a frequency component on a lower frequency side and a frequency component on a higher frequency side of the center frequency of a spectrum of the monitor light and monitors power values of the frequency components. A difference value between the power values of the respective frequency components is calculated and a relation of relative phase between signals used for driving respective optical modulation parts is controlled based on the difference value.