Patent ID: 8693870

Claim:
A control apparatus comprising: a filter which has filter characteristics that pass only a frequency component corresponding to a baud rate, the frequency component is included in polarization-multiplexed output light that is output from a polarization multiplexing light modulator which performs light modulation on two systems independent of each other, polarization-multiplexes light signals of the two systems subjected to the light modulation, and outputs the polarization-multiplexed light signals; an output monitor which monitors the frequency component that is passed by the filter; and a control unit which controls a delay time difference at a stage where the light signals of the two systems forming the polarization multiplexing light modulator are polarization-multiplexed based on a monitor result of power of the frequency component, wherein the control unit comprises: a storage unit which stores a correspondence table of the delay time difference according to the power of the frequency component, the correspondence table set in such a manner that the delay time difference is “0” or one symbol time when the power is a maximum value in the correspondence table and the delay time difference is a half of the symbol time when the power is a minimum value in the correspondence table; and a control signal output unit which outputs a control signal for controlling the delay time difference in accordance with the amount of the delay time difference corresponding to the monitor result of the power of the frequency component.