Optical Switching Systems and Flex-Grid Technologies

Driven by future (beyond 5G and 6G) services and applications, optical networks are required to support an ever increasing and more dynamic data traffic in a flexible and efficient manner. In this evolutionary scenario, an optical bandwidth allocation based on a fixed-grid spectrum is no longer suitable for addressing the envisioned multi-Tb/s capacity links and dynamic connectivity, while ensuring an optimal usage of the network resources and the available infrastructure. Thus, optical switching systems require advanced technologies to support this novel flexible paradigm. This chapter presents the fundamental building blocks, the network elements and technologies enabling elastic optical networks, flex-grid channel allocation and routing, as well as multiple and advanced switching operations. This includes the bandwidth-variable optical cross-connect, wavelength selective switch, and reconfigurable optical add/drop multiplexer, as well as flexible transceivers, such as the (sliceable) bandwidth/bitrate variable transceiver, and software defined networking-based control and orchestration. Commercial technologies as well as latest research solutions currently under investigation are presented and discussed highlighting a path for optical switching systems enabling flexible operation and dynamic high-capacity connectivity for both optical and data center networks.