Nanosecond photonic integrated multicast switch for low-latency optical wireless data center networks

Optical wireless data center networks (OW-DCNs), featur- ing no cable complexity, low latency, and high throughput, are highly attractive for the next generation of DCNs, while photonic integration provides a compact, low-power, and low-cost solution. In this Letter, we propose a novel, to the best of our knowledge, OW-DCN architecture using pho- tonic integrated multicast switches (PIC-MCSs) to realize fast optical switching and multicast operation between top- of-the-rack switches (ToRs). By properly turning on/off the transmission channels of a semiconductor optical amplifier (SOA)-based PIC-MCS, the optical signals are directed to different target ToRs via arrayed waveguide grating routers (AWGRs) and free-space links. A 4×2 PIC-MCS with loss- less multicast operation has been designed and fabricated. An OW-DCN of 4×4 interconnected racks has been exper- imentally demonstrated with the chip and a 4×4 AWGR. The results confirm the performance of low-latency switch- ing, dynamic bandwidth reallocation, and WDM multicast transmission. Error-free operation at 10 Gb/s OOK with a power penalty of less than 1 dB is achieved, showing a neg- ligible impact of cross talk on the PIC-MCS.