7424x 7424 Optical Circuit Switch With 1.4 μs Switching Time Enabled by Silicon-Photonic 64-Port Space Switches and Burst-Mode Coherent Receivers

High-port-count optical switches will provide an attractive approach to innovating intra-data center networks as they resolve the bandwidth and power problems now emerging with the saturation of Moore's law. Optical switches that provide several thousand ports and microsecond switching time are a future proof solution. In this article, we propose a high-port-count and fast optical circuit switch that is constructed by combining M x M space switches, N x N wavelength-routing switches, and burst-mode coherent receivers. By scaling up the available number of space switch ports ( M ) and wavelengths ( N ), the total port count ( MN ) can be expanded at the expense of higher loss. In this work, we use Silicon-Photonic technology to fabricate a low-loss (similar to 9.4 dB) monolithically integrated 64 x 1 selector and tunable filter (TF) equipped with on-chip polarization diversity circuits. The TF is essential for increasing the wavelength number ( N ), as it can reject undesired signals in the delivered wavelength division multiplexing (WDM) channels before coherent reception. We also develop a bust-mode coherent receiver that uses adaptive equalization of the Stoke-vector and constant modulus algorithms to provide fast acquisition. To verify the availability of high port counts and fast switching times, experiments are performed on our optical switch using 116-channel WDM signals, each wavelength carrying a 128-Gbps DP-QPSK signal. 7424 x 7424 optical switching with 1.4-mu s switching time is validated by our newly developed burst-mode coherent receiver and monolithically integrated Silicon-Photonic space switch with tunable filter. To the best of our knowledge, the reported port count is the highest confirmed with microsecond order switching time.