System-Level Demonstration of a 3D-Integrated Optical 16×16 Benes Switch

In this work, we present the first fully packaged 16×16 Benes optical switch based on 3D photonic integration operating in the O-band, and demonstrate, for the first time, its system-level evaluation. The 3D switch employs a dual-layer architecture with 56 thermo-optic 2×2 Mach-Zehnder interferometer-based crossbar units and vertical multimode interferometers enabling the transition between the two parallel waveguiding layers and effectively eliminating in-plane waveguide crossings. The static optical performance of the 3D optical switch prototype was evaluated based on insertion and polarization-dependent losses, crosstalk, power consumption, and switching speed. The 3D switch is fabricated on a polymer-based photonic platform, known as PolyBoard, which is suitable for developing 3D structures. In order to perform a system-level demonstration, the switch was integrated into a 25 Gb/s full-duplex optical link using a commercial Network Interface Card and SFP transceivers. Stable throughput was maintained across back-to-back and extended-reach fiber links up to 10 km, demonstrating the viability of this 3D-integrated switch for scalable, energy-efficient intra-data center interconnect.