Patent ID: 7181094

Claim:
An apparatus for controlling an acousto-optic tunable filter including a plurality of input ports for a reference signal and a wavelength-division-multiplexed signal, and a plurality of output ports for the reference signal and a drop signal dropped from the wavelength-division-multiplexed signal, the apparatus comprising: a radio-frequency-signal generator that generates a radio-frequency signal; an optical monitor that monitors a first intensity of the reference signal and a second intensity of the drop signal output from the output ports; and a field-programmable gate array that includes a reference-frequency determining unit that determines, based on the first intensity, a first frequency of the radio-frequency signal that causes the acousto-optic tunable filter to output the reference signal; a temperature detecting unit that detects a temperature of the acousto-optic tunable filter; a frequency calculating unit that calculates a second frequency of the radio-frequency signal that causes the acousto-optic tunable filter to output a drop signal of a desired wavelength based on the second intensity, the first frequency, the temperature detected, and a temperature-dependent output characteristic of the acousto-optic tunable filter measured in advance; and a control unit that controls the radio-frequency-signal generator to generate the radio-frequency signal of the second frequency calculated.