Patent ID: 8200091

Claim:
A wavelength division multiplexing device having a plurality of dispersion compensators for respectively compensating for dispersion of a plurality of optical signals of different frequencies, comprising: an optical amplifier to amplify one of a plurality of optical signals of different frequencies that is modulated using a low-frequency signal; a dispersion compensator to compensate for dispersion of an optical signal output from the optical amplifier; a detection unit to detect the low-frequency signal in the optical signal; and a control unit to control to make the dispersion compensator perform a compensation operation by determining that the optical signal is being input when a low-frequency signal is detected in the optical signal in the detection unit, and to control to stop a compensation operation of the dispersion compensator by determining that there is an input break of the optical signal when a low-frequency signal is not detected in the optical signal in the detection unit; wherein the control unit includes storage unit to store information indicating whether or not a dispersion compensation amount is adjusted, and outputs, to the dispersion compensator, a previous dispersion compensation amount as an initial value when a low-frequency signal is detected in the detection unit and information indicating that a dispersion compensation amount is adjusted is stored in the storage unit.