Patent ID: 7570843

Claim:
An optical modulation element module, comprising: a Mach-Zehnder type optical modulation element having a Mach-Zehnder type waveguide unit with two branched waveguides formed on a substrate with electro-optical effect and two independent modulation electrodes disposed corresponding to each branched waveguide, optical input and output units for inputting and outputting a light wave to and from the optical modulation element, and a modulation signal input unit for inputting the modulation signal into the modulation electrodes, in a case, further comprising: a transformer branching unit which has the modulation signal input unit formed as one terminal, which divides the modulation signal from the modulation signal input unit into two modulation signals, and which applies the divided modulation signals to each modulation electrode, wherein, in the transformer branching unit, an electric power branching rate of an output port is 1:1 and a phase difference of each branched signal is 180°, and further in the transformer branching unit, an input impedance is matched with an impedance of the modulation signal input unit with an impedance value of 50 Ω, and an output impedance is matched with a line impedance of each modulation electrode with an impedance value of 50 Ω or less.