Patent ID: 7957653

Claim:
An optical frequency shift keying modulation system comprising: a first sub Mach-Zehnder waveguide (MZ A ); a second sub Mach-Zehnder waveguide (MZ B ); a main Mach-Zehnder waveguide (MZ C ) comprising: an input part of an optical signal, a branching part, the branching part being configured to be connected to the input part, the branching part being connected to the MZ A and the MZ B , the optical signal being branched at the branching part into the MZ A and the MZ B , the first sub Mach-Zehnder waveguide (MZ A ), the second sub Mach-Zehnder waveguide (MZ B ), a combining part, the combining part being connected to the MZ A and the MZ B , the optical signal outputted from the MZ A and the MZ B being combined at the combining part, an output part outputting the optical signal combined at the combining part; a first electrode (electrode A) of the first sub Mach-Zehnder waveguide (MZ A ); a second electrode (electrode B) of the second sub Mach-Zehnder waveguide (MZ B ); a third electrode (electrode C) of the main Mach-Zehnder waveguide (MZ C ); a signal source for applying either one or both of a modulation signal and bias voltage to the first electrode, the second electrode and the third electrode; and an output signal phase adjusting part for adjusting a phase difference between an upper side band signal and a lower side band signal, the upper side band signal and the lower side band signal being outputted from the output part.