Patent ID: 7711215

Claim:
An optical amplitude modulation system comprising: a Mach-Zehnder waveguide, the Mach-Zehnder waveguide comprising: an input part of an optical signal; a branching part where the optical signal is branched; a first arm, the first arm being configured to act as a waveguide; wherein one of the optical signal branched from the branching part propagates though the first arm; a second arm, the second arm being configured to act as a waveguide, wherein the remaining optical signal branched from the branching part propagates though the second arm; a combining part combining the optical signals, the optical signals outputted from the first arm and the second arm; and an output part outputting the optical signal, the optical signal being combined at the combining part; a first intensity modulator provided on the first arm, the first intensity modulator controlling amplitude of the optical signal propagating through the first arm; a second intensity modulator provided on the second arm, the second intensity modulator controlling amplitude of the optical signal propagating through the second arm; a first electrode (electrode A) of the first intensity modulator; a second electrode (electrode B) of the second intensity modulator; a third electrode (electrode C) controlling a phase difference between the optical signal propagating through the first arm and the optical signal propagating through the second arm, a modulation signal being applied to the third electrode; and a signal source part, the signal source part comprising: a first signal source for supplying bias voltage, the bias voltage being applied to the first electrode (electrode A), the second electrode (electrode B), and the third electrode (electrode C); and a second signal source, which is a high frequency signal source, for supplying a radio frequency signal to the third electrode (electrode C), wherein the second signal source comprises: a third harmonic signal generator for generating an electric signal (3f m ), the electric signal (3f m ) having a frequency three times the frequency of a basic signal (f m ); a phase adjusting part for adjusting a phase difference between a phase of the basic signal (f m ) and a phase of the electric signal (3f m ), the basic signal (f m ) being outputted from the second signal source, the electric signal (3f m ) being outputted from the third harmonic signal generator, the electric signal (3f m ) having a frequency three times the frequency of the basic signal (f m ); and a signal intensity adjusting part for adjusting intensity of the basic signal (f m ) or the electric signal (3f m ), the basic signal (f m ) being outputted from the second signal source, the electric signal (3f m ) being generated from the third harmonic signal generator, the electric signal (3f m ) having a frequency three times the frequency of the basic signal (f m ).