Large-Scale and Multiband Silicon Photonics Wavelength Cross-Connect Switch With FSR-Free Grating-Assisted Contra-Directional Couplers

The recent advancement of cloud computing including AI applications requires a large networking capacity in datacenters resulting in a large power consumption at the same time. Optical switches significantly improve energy efficiency in datacenter networks, and silicon photonics enables the optical switch to operate faster than microseconds and be highly integrable for co-integration with GPUs. To support such high-capacity interconnect and switching, flexible use of multiple lanes and wavelength division multiplexing is essential, which can be implemented by a wavelength selective switch or wavelength cross-connect (WXC) switch. We proposed a novel silicon photonics WXC switch with free-spectral-range (FSR)-free grating-assisted contra-directional couplers (C-DCs) and Mach-Zehnder interferometers (MZIs), where extremely broadband operation is expected because of the unlimited FSR. In this paper, we demonstrate a largest ever port- and channel-count, 16 × 16 ports and 16 wavelength channels over the C+L-band, monolithically integrated WXC switch with 256 FSR-free grating-assisted C-DCs and 1,024 thermo-optic MZIs. Further extended multiband operation from the O-band to U-band will be potentially available by implementing two additional design considerations.