Towards a Hybrid Architecture by Introducing Coherent Pluggable Transceivers in IP-Optical Core Networks with Optical Cross-Connects

During the previous years, there has been a big technological advancement in Digital Signal Processing (DSP) and coherent pluggable optics, which enabled a considerable increase in the data rate and a step towards economical packet-optical integration, respectively. This caused the network operators to start wondering whether an architectural change should take place in their infrastructure. Coherent Pluggable Transceivers (CPTs), already being a success story for Data Center Interconnect (DCI), have grown to be used not only in metro networks but, as of recently, also in some parts of the core. The latter constitutes a major use case for the Multi-Source Agreement (MSA) OpenZR+. As many network operators can have good reasons to stick with the traditional standalone transponder equipment, this paper explores a hybrid solution combining CPTs and transponders to fully exploit the advantages of the two technologies. More specifically, we balance the trade-off between using cheaper pluggable modules directly on the IP router and powerful standalone flexible transponders with a gray interface. Although the integration of colored optics in the router was already proposed about a decade ago with Cisco’s IPoD-WDM, we find that this time it is more appealing in terms of power consumption, module size, and equipment cost. Furthermore, we look closer at a collapsed packet-optical integrated architecture of Hop-by-Hop lightpath connections as opposed to a multilayer one, which also uses Optical Cross-Connects (OXCs). We show that a hybrid solution using both architectures yields the best results for improving network metrics and minimizing hardware costs. We contribute an Integer Linear Program (ILP) to solve the dimensioning problem for realistic countrywide topologies.