Silicon-Based Flexible-Grid Mode- and Wavelength-Selective Switch Utilizing Microring Resonators and Y-Junctions

In this article, a design of integrated flexible-grid mode- and wavelength-selective switch consisting of silicon-based symmetric Y-junctions and double-series coupled microring resonators with interferometric couplers is introduced in detail. Using thermal tuning, the described device is capable of routing each mode and wavelength signal from the input port to any output port flexibly and independently, forming different bandwidths as needed. For fixed field coupling coefficients, the device can support multiple different wavelength-channel spacings. A silicon-based flexible-grid 1 × 6 mode- and wavelength-selective switch is carefully designed and analyzed as an example. The designed device works for two mode channels and three wavelength channels. The wavelength-channel spacing can vary from 0.10 to 0.80 nm and the 3-dB bandwidth changes from 0.08 to 2.00 nm. When the wavelength-channel spacing is set to be 0.80 nm, the extinction ratio is greater than 50.90 dB and the crosstalk is less than -15.36 dB.