Densely integrated photonic devices based on microring resonators for use in access networks

A reconfigurable optical add-drop multiplexer as well as a 1x4x4 reconfigurable λ router, designed for use in the second telecom window, are demonstrated. The devices that each have a footprint less than 2 mm$_{2}$ are based on thermally tunable vertically coupled microring resonators fabricated in $Si_{3}N_{4}$/$SiO_{2}$