WAVEGUIDE-TYPE ATTENUATOR AN WAVEGUIDE TYPE OPTICAL MODULATOR

摘要

PROBLEM TO BE SOLVED: To provide a novel waveguide-type modulator which realizes proper transmission characteristic without having to depend on the various intensity of the attenuation of an attenuator section of a waveguide-type modulator having an optical modulation section and the attenuator section. SOLUTION: The optical modulation section 2 is constituted by forming a first optical waveguide 5 of a Mach-Zehnder type within a substrate 4, having an electro-optic effect and forming a first signal electrode 6 and a first grounding electrode 7 on the substrate 4. The attenuator section 3 is constituted, by forming a second optical waveguide 8 so as to be connected in series to the first optical waveguide 5 within the substrate 4 and forming a second signal electrode 9 and a second grounding electrode 10, without having to form a buffer layer. The end of the second signal electrode 9 is provided with a capacitor 15, which is a noise removing means for removing the high-frequency noise generated from a control electrical signal to be impressed to this signal electrode.