To efficiently search for a suitable compensation dispersion amount without providing a dispersion amount detector.

A receiver 123 receives signal light of a predetermined bit rate and signal light of a bit rate different from the predetermined bit rate from a transmitter 110 before performing data communication. In a dispersion amount control part 124, unit variation of the compensation dispersion amount by which a variable dispersion compensator 122 performs dispersion compensation, corresponding to the bit rate of the signal light received by the receiver 123 is set. The dispersion amount control part 124 controls the variable dispersion compensator 122, changes the compensation dispersion amount by set unit variation at a time and searches for a predetermined compensation dispersion amount for each signal light received by the receiver 123. The dispersion amount control part 124 calculates a compensation dispersion amount for the variable dispersion compensator 122 to apply the dispersion compensation to the signal light received from the transmitter 110 when data communication is performed based on a result of searching the predetermined compensation dispersion amount.