Tunable passband flattened 1-from-16 binary-tree structured add-after-drop multiplexer using SiON waveguide technology

A tunable, flat-passband, 1-from-16 add/drop multiplexer for wavelength-division-multiplexing networks is presented. The device is realized in high-index-contrast silicon-oxynitride waveguide technology and is based on cascaded resonant coupler filters in the form of a mirrored binary tree. Tunability is obtained using the thermo-optic effect. The isolation of the transit channels at the drop port is better than 18 dB, and the rejection of the drop channel at the output port is 26 dB.