Disaggregated optical-layer switching for optically composable disaggregated computing [Invited]

Disaggregated computing has been widely investigated to support the continuous progress in computing performance and overcome the slowdown of Moore’s law. It involves a flexible and optimal interconnection of heterogeneous compute nodes, such as the CPU, GPU, xPU, memory, and storage, to offer an efficient computing environment for various applications. Such a scheme inherently requires high network performance, including low latency, high capacity, determinism, and energy efficiency, all of which are simultaneously achieved through the introduction of optical-layer switching. This paper presents the application of optical-layer-switching architectures to disaggregated computing. Networks associated with disaggregated computing are classified into intra- and interserver networks. Focusing on the intraserver network, a holistic concept of optically composable disaggregated computing (OCDC) is discussed, along with its technological direction toward future digital infrastructure (i.e., the computing continuum). To realize OCDC, scalable and flexible optical switch technologies, as well as their dynamic and automatic control and management mechanisms, are indispensable. Previous studies have reported 32×32 silicon photonic switches that can form a nine-stage Clos topology with a radix of 131,072 and a machine-processable function description model for optical-layer switching, called the functional block-based disaggregation model (FBD model) that is capable of automating the operation, administration, and management of any optical physical topology in cooperation with upper-layer operating systems. This study examines their applicability to OCDC. The superior energy performance and scaling of an OCDC system equipped with optical matrix switches, such as silicon photonic switches, with respect to the conventional one big electrical packet-switching approach based on the reported wall-plug power consumption is also presented. The potential applicability of the FBD model as an essential control and management system for the optical layer of OCDC is evaluated through numerical experiments.