Integrated High-Performance Two-Stage Ratiometric Wavelength Monitors On Silicon

We design and fabricate an integrated high-performance two-stage ratiometric wavelength monitors (RMWMs) on silicon. The first stage is a coarse wavelength monitor with a wide working range based on two unbalanced Mach-Zehnder interferometers acting as edge filters. The second stage is a fine wavelength monitor with picometer wavelength resolution utilizing two tunable microrings acting as edgefilters. The highest measured wavelength resolution can reach 1.6 pm in a 0.7-nm-wide wavelength range for the fine wavelength monitor. The working wavelength range can reach about 55 nm with a resolution of 0.1 nm for the coarse wavelength monitor. By thermally tuning the resonant wavelengths of microrings, we can obtain high resolution on the whole 9.6-nm free spectral range of the microrings. The influence of perturbation of temperature is also discussed. This letter can solve the problem that the measurable wavelength range and resolution limit each other in a conventional RMWM.