Two-step scheduling framework for space-wavelength modular optical interconnection networks

Current interconnection architectures based on electronics are approaching their physical limitations especially in terms of interconnection wiring and power density. To overcome these issues, the flexibility and the scalability of optical technologies can be exploited. This paper considers a modular optical interconnection architecture that consists of multiple cards, supporting a fixed number of ports and interconnected through a passive optical backplane. A two-step scheduling framework (TSS) is proposed, which exploits the modularity of the architecture and the existing scheduling algorithms, while satisfying the peculiar scheduling constraints of the architecture. In TSS, an intra-card step decides the wavelength switching configuration and then an inter-card step decides the space switching configuration. Each step can be run in parallel, on the cards and on the wavelengths, respectively. TSS is compared against a single-step scheduler suitable for non-modular architectures, under different traffic patterns and architecture configurations. TSS performs better in terms of lower packet delay, higher throughput and lower computational complexity. Finally, the possibility of increasing the packet transfer rate (transfer speedup) can be included in TSS without additional complexity and is especially beneficial for the bursty and skewed traffic patterns, typically experienced in real scenarios.