Node architecture with unidirectional intra-node connections for subsystem-modular optical cross-connects

To cope with the scalability limitations of conventional optical cross-connects (OXCs), previous studies have introduced a subsystem-modular OXC architecture, which comprises multiple low-port-count switch modules called OXC-subsystems. This architecture can employ an intra-node structure that connects OXC-subsystems sequentially within a node. While this architecture allows for low-port-count OXC-subsystems to be used, it includes redundant intra-node connections between OXC-subsystems to ensure high flexibility of intra-node routing, which can lead to an increase in the number of OXC-subsystems deployed. This paper proposes a node architecture that adopts unidirectional intra-node connections, aiming to reduce redundant intra-node fibers and improve the utilization efficiency of subsystem ports. In the proposed node architecture, OXC-subsystems are connected in one direction, which can help to avoid redundant bidirectional connections and enable more ports to be used for inter-node connections. We formulate the network model with the proposed node architecture as an integer linear programming problem. For large-scale problems, we develop heuristic algorithms for routing and wavelength assignment to cope with the constraints introduced by unidirectional intra-node connections. Numerical results demonstrate that the network with the proposed node architecture reduces the total number of OXC-subsystems compared to that with the benchmark architecture in static network design. The results also confirm that the proposed architecture achieves the same blocking performance as the benchmark system while reducing the number of OXC-subsystems by up to 17.4%.