How Optical Technologies Can Innovate Intra Data Center Networks

This paper discusses how optical technologies can bring innovation to intra data center networks. The most promising technique is the electrical-packet/optical-circuit hybrid switching network. Its key advantage stems from using large port-count optical switches, which enables flat and unified interconnects among ToRs in a data center; an architecture not possible with electrical switches due to the limited switch chip radix. Such optical switches can be implemented in a way similar to the widely deployed ROADM/OXC that leverages wavelength routing and space switches. When matched to the radix of merchant silicon switches for ToR, the parallel configuration of optical switches yields virtually blocking-free networks, and satisfactory link utilization, say more than 0.6, is expected. With regard to the key issue of optical switch control, the proposed configuration enables decentralized and asynchronous control and the latency is shown to be less than 20 $\mu$ s (L=200m), which is a deterministic value without the long tail as seen in electrical packet switch networks. The presented hybrid switching network will pave the way to future data center networks by resolving the problems expected with the envisaged demise of Moore’s law.