Multi-Domain Transparent Service Provisioning in Multi-Band Optical Networks

Given the sustained traffic increase, transport optical networks need to evolve to provide additional capacity. While it is commonly admitted that long term solutions will rely on Spatial Domain Multiplexing (SDM) -- either by deploying bundles of standard single mode fibers or multi-core fibers --, short and mid-term solutions can achieve a more efficient usage of the fiber optical spectrum capacity by exploiting the different bands (beyond the C -band and even the already commercially available $\mathrm{C}+\mathrm{L}$ systems). However, path computation in a multi-band environment becomes significantly more complex, critically due to physical layer impairment (PLI) effects such as Stimulated Raman Scattering (SRS). While this aspect has been explored in the context of single domain networks, the case of transparently connected multi-domain networks remains mostly unexplored, given the challenges associated to the trade-off between scalability and topology visibility/network abstraction. In this paper, we present a proof-of-concept of a multi-domain media channel service provisioning transparently across emulated domains (optical line systems) leveraging the existence of multiple bands, using a hierarchical arrangement of controllers, where each domain relies on a dedicated OLS SDN controller. Such OLS controllers export a Transport-API (TAPI) North Bound Interface, extended to encompass PLI information about the supported optical bands. The parent orchestrator is responsible for path computation using abstracted information, and for orchestrating the provisioning by delegating segment control to the OLS controllers while ensuring a satisfactory QoT given the connection reach and physical layer impairment abstracted information. We evaluate aspects such as control plane latency and overall feasibility.