Microring-based ratio-metric wavelength monitor on silicon.

An integrated dual-ring ratio-metric wavelength monitor (DR-RMWM) with ultra-high wavelength resolution and compact size is demonstrated. Two microrings are used as the edge filters and designed to achieve an "X-type" spectral response in a particular wavelength range. It is fabricated with the CMOS-compatible fabrication process on the silicon-on-insulator. The measured wavelength resolution is 5 pm in a 1.2 nm wide wavelength range. By tuning the resonant wavelength thermally, the functional wavelength range can be shifted. The DR-RMWM can find applications in wavelength monitoring systems, especially the on-chip systems.