Patent ID: 7783138

Claim:
A phase tracking monitor integrated with a Mach-Zehnder interferometric modulator comprising: an optical waveguide element comprising: an input optical waveguide for receiving an input optical signal; two branched optical waveguides, each guiding a portion of the input optical signal; an input Y-junction optically coupling the input optical waveguide to the two branched optical waveguides; an output optical waveguide for optically coupling to an output optical fiber; and an output Y-junction optically coupling the two branched optical waveguides to the output optical waveguide for causing the portions of the input optical signal propagating from the two branched optical waveguides to interfere with each other; a substrate comprising an electro-optic dielectric material for supporting the optical waveguide material on an upper surface thereof; a set of electrodes for applying an electric field proximate to the two branched optical waveguides for modulating a phase of the portions of the input optical signal propagating therethrough to generate a modulated optical signal having an on-state and an off-state at the output Y-junction; wherein in the on-state the modulated optical signal generates a guided mode in the output optical waveguide; and wherein in the off-state the modulated optical signal generates a radiating mode comprising a left lobe and a right lobe in the substrate; a fiber block attached to an output edge of the substrate for stably supporting the output optical fiber to receive the guided mode from the output optical waveguide; a first photodetector for generating a first photocurrent in response to light transmitted from the output edge of the substrate; and light-blocking material disposed between the output edge of the substrate and the first photodetector for blocking a portion of the radiating mode and the guided mode that reach the first photodetector.