Nanosecond-Level Optical Switching for Flexible and Resilient Fronthaul Networks

This paper presents a novel, ultra-low latency fronthaul networking approach based on nanosecond (ns)precision optical switching with advanced synchronization. We propose and demonstrate a comprehensive control architecture that integrates Precision Time Protocol (PTP)-based time alignment with semiconductor optical amplifier (SOA)-based optical switches, enabling coordinated, jitter-minimized switching with accuracy as fine as 100 ns. Two primary synchronization methods are explored: a distributed hardware approach employing dedicated timing devices for simultaneous switch configuration, and "SyncNet," a Software-Defined Networking (SDN) controller utilizing time information inspired by reverse PTP. Experimental validation on a commercial Open RAN 5G system shows that our fronthaul switching framework achieves exceptional reliability, evidenced by only 0.00024% packet loss during link recovery while maintaining steady throughput (uplink: 1.03 Mbps, downlink: 1.01 Mbps) over repeated switching events. The proposed architecture supports dynamic reconfiguration for rapid link recovery and energyefficient, traffic-adaptive resource allocation. Our results establish a robust foundation for next-generation fronthaul networks, delivering deterministic performance and flexibility aligned with 6G requirements. This work directly addresses the escalating needs for ultra-low latency, high reliability, and energy efficiency in emerging mobile and AI-driven applications.