O-band 32 × 32 silicon photonic switch with double Mach-Zehnder switch elements

Silicon photonic switches are expected to offer energy efficient switching in future data center networks and artificial intelligence/machine learning clusters. In this paper, we report a strictly non-blocking silicon photonic switch with 32 inputs and 32 outputs based on a path-independent insertion-loss topology, which consists of double Mach-Zehnder (MZ) switch elements to improve the crosstalk performance. The switch chip, therefore, contains 2048 thermo-optic MZ switches. The switch chip was fabricated using a complementary metal-oxide-semiconductor pilot line with the 45-nm technology. The fabricated switch chip was flip-chip bonded to a 2114 land-grid-array (LGA) ceramic interposer, and the electrodes on the chip were connected to a control circuit board. To control the 2048 MZ switches through the LGA 2114 interposer, a single arm of each MZ switch was electrically wired, rather than both arms as in our previous 32 × 32 switches. 99.2% of the MZ switches were connected and operated. The fabricated switch exhibited minimum, maximum, and average on-chip insertion loss of 9.3, 15.6, and 11.8 dB, respectively, and a crosstalk of less than -20 dB over a 70-nm bandwidth. Moreover, using a 100G-ER4 optical transceiver, we demonstrate 100-Gbps signal transmission with a bit error ratio of less than 1 × 10^-3, which is mostly due to the amplifier noise.