Patent ID: 8774566

Claim:
An optical waveguide element module comprising: an optical waveguide formed on a substrate; an optical waveguide element having a modulation electrode for modulating an optical wave propagating through the optical waveguide; a connector where an external signal line for inputting a modulation signal into the modulation electrode is connected; and a relay line formed on a relay substrate to connect the connector and the modulation electrode, wherein the relay line is a coplanar-type line, in which a signal electrode is interposed between ground electrodes, an impedance of the relay line changes stepwise so as to suppress reflection of the modulation signal in the optical waveguide element module, a filter circuit including a capacitor is arranged in a middle of the relay line, and a length of the relay line in a block of each stage is less than a quarter of a microwave wavelength used in the modulation signal.