Analysis and design of micro-ring resonator as an add drop filter for Coarse Wavelength Division Multiplexing (CWDM) application

An optimal micro-ring resonator with laterally coupled waveguides is presented in this paper. The proposed resonator is optimized to work as an add-drop filter for Coarse Wavelength Division-Multiplexing (CWDM) system which follows ITU-T G.694.2 standard. Optimized micro-ring resonator should have wide Free Spectral Range (FSR) and high Quality Factor (Q) to accommodate many channels and high Extinction Ratio (ER) to avoid crosstalk. From the 3-D structure rib waveguide, we converted it to the effective 2-D structure. By using the excitation pulse as an input signal, this resonator was simulated at CWDM wavelength 1.55μm. With 0.2μm wide ring waveguide cavities and by varying radius of microring, we found out that the optimal radius for the resonator is 4.5μm which can have Q in several hundred and free spectral range of 30nm. Based on this optimal radius, the resonator was simulated with various width of waveguide to get the optimized performance. With width of waveguide 0.35μm, the FSR can be as wide as 30nm and Q of nearly 1550.