PERSPECTIVES

driven by power- and time-effi cient regen-eration. Recently, integrating circuit switch-ing with packet switching has been examined with the goal to create hybrid networks within individual data centers ( 2, 3), using optics to provide more effi cient services for applica-tions relying on large fl ows of data. The key insight is that by quickly reconfi guring opti-cal paths, changes in traffi c workloads can be supported. As we envision optical network-ing interconnecting tightly integrated rack-on-chip designs, providing both on- and off-chip connections, we need even faster opti-cal reconfi guration and cost-effective inte-gration to support the highly variable traffi