Deterministic optical time-slot scheduling and performance evaluation via time-aware resource allocation in metro all-optical spine-leaf networks

The rise of time-sensitive applications has intensified the need for deterministic transmission across networks. As computing and service functions are shifted toward the edge, metro networks have become the key interconnection layer between access and core domains. However, conventional optoelectronic-switched network architectures, which rely on statistical multiplexing and slow reconfiguration, fail to meet stringent latency and jitter constraints. To overcome these challenges, this paper focuses on a scalable all-optical spine-leaf network architecture by introducing an optical time-slot switching (OTS) framework. OTS offers fine-grained switching and low-latency transmission; however, achieving deterministic transmission over shared optical resources remains challenging due to slot contention and insufficient coordination in existing scheduling schemes. Therefore, we propose a time-aware wavelength and slot allocation (TA-SA) scheme that allocates transmission windows (TWs) according to individual flow parameters, including arrival time, period, and jitter tolerance. We formulate an integer linear programming model and a heuristic algorithm to jointly optimize TW placement and wavelength-slot mapping under strict QoS constraints. To analyze worst-case network performance, deterministic network calculus is adopted to model delay and backlog bounds for different scheduling schemes. Simulation results show that TA-SA not only guarantees end-to-end latency and jitter constraints but also improves average resource utilization by over 34.9% compared to the existing scheduling schemes. Moreover, the proposed scheme significantly reduces buffer occupancy under increasing traffic loads, demonstrating its scalability and effectiveness for deterministic transmission in metro all-optical networks.