An eight-channel add-drop filter using vertically coupled microring resonators over a cross grid

An eight-channel add-drop cross-grid vertically coupled microring resonator (VCMRR) filter is proposed and demonstrated. The cross grid comprises a gr id-like array of buried channel waveguides which perpendicularly cross thro ugh each other, VCMRR's at each of the cross-grid nodes serve as the wavele ngth selective add-drop filters, Measured crosstalk levels at the crossings are typically less than -30 dB, Rings with a nominal radius of 10 mu m are used to achieve a free-spectral range of 20 nm and optical bandwidths of 1 nm, while changes of the radii in increments of 50 nm lead to a nominal ch annel spacing of 5.7 nm.