Directional coupler and mach-zehnder modulator using such coupler

摘要

A dual output electro-optical modulator (100) for modulating an optical signal by an electrical signal (285), comprising a Mach-Zehnder interferometer with an input path (102), two arms (103, 104) and a directional coupler (105), wherein the directional coupler comprises two waveguides on a planar substrate (101) defining two inputs, two outputs and a coupling region between the inputs and the outputs where the waveguides are in close proximity to each other so as to cause coupling between them. The coupling region of the directional coupler comprises a strong coupling region and in that the length of parallel sections of optical waveguides in the coupling region is less than 35% of the length of the strong coupling region.