Ring-resonator filters in silicon oxynitride technology for dense wavelength-division multiplexing systems

The design and characterization of ring-resonator-based filters with free spectral ranges of 100 and 50 GHz by use of ${\mathrm{SiO}}_x{\mathrm{N}}_y$ technology is presented. Fiber-to-fiber insertion losses of 4.4 dB on the drop port and 2.1 dB on the through port have been achieved for a single-ring filter. An interleaver filter for a 25-GHz spaced dense wavelength-division multiplexing system with two cascaded rings is demonstrated. The filter has a 7.4-GHz bandwidth at $-1 \mathrm{dB}$ and an extinction ratio of 15 dB and is polarization independent.