Patent ID: 7660027

Claim:
An optical modulator for outputting an optical signal which is modulated based on a plurality of alternating current signals, the optical modulator comprising: a Mach-Zehnder type optical interference system, formed on an electro-optic crystal, including a first optical waveguide and a second optical waveguide; a first electrode operable to apply, to the first optical waveguide of the Mach-Zehnder type optical interference system, a first electric signal based on a first alternating current signal; a second electrode operable to apply, to the second optical waveguide of the Mach-Zehnder type optical interference system, a second electric signal based on a second alternating current signal having a different frequency from the first alternating current signal; and a bias setting section operable to set average direct current levels of the first and second electric signals based on signal frequency information which indicates a magnitude relation between a maximum frequency of the first alternating current signal and a maximum frequency of the second alternating current signal.