Scaling wavelength selective switches for multi-band and space-division-multiplexed networks

This paper investigates the practical scalability of wavelength selective switching technology for the emerging multi-band and space-division-multiplexed (SDM) networks. Wavelength selective switching architectures are introduced for multi-band SDM networks. The switching capacity is analyzed for both weakly coupled and strongly coupled SDM networks. Key bottlenecks for scaling up toward multi-band and more spatial modes are identified. Contrary to the conventional view that liquid crystal on silicon (LCOS) was the only technological obstacle, the manufacturability of free-space optics with high numerical apertures and constraints on the optical dimensions also brought significant challenges for the development of highly integrated wavelength selective switches for multi-band SDM networks.