Patent ID: 7315676
Filing Date: 2008-01-01
Classification: G02B,G02F

Abstract:
1. An optical modulator, comprising: a substrate having an electro-optical effect; first and second Mach-Zehnder type optical waveguides formed in series on said substrate; a first signal electrode section provided on said first Mach-Zehnder type optical waveguide for being supplied with a clock signal; a second signal electrode section provided on said second Mach-Zehnder type optical waveguide for being supplied with a data signal; a first bias electrode section provided on said first Mach-Zehnder type optical waveguide for being supplied with a bias voltage; a second bias electrode section provided on said second Mach-Zehnder type optical waveguide for being supplied with another bias voltage; a first coupler provided on the outgoing side of said first Mach-Zehnder type optical waveguide for fetching monitor light; a second coupler provided on the outgoing side of said second Mach-Zehnder type optical waveguide for fetching monitor light; a first monitor photodiode for detecting a light signal of the monitor light fetched by said first coupler; a second monitor photodiode for detecting a light signal of the monitor light fetched by said second coupler; a first bias voltage control section for controlling the bias voltage to be supplied to said first bias electrode section based on the light signal detected by said first monitor photodiode; and a second bias voltage control section for controlling the bias voltage to be supplied to said second bias electrode section based on the light signal detected by said second monitor photodiode; said first coupler including two input waveguides through one of which light from said first Mach-Zehnder type optical waveguide is inputted, a waveguide coupling element for coupling said two input waveguides with a distance d the distance d width w