Multiple access stable frequency dissemination via fiber-optic ring network

A hierarchical multi-access scheme is proposed for stable frequency dissemination in fiber-optic ring networks. The system features primary and secondary nodes, where a phase-locked loop at the primary site suppresses fiber-induced noise to generate a high-stability signal. Secondary nodes receive optical signals from the local and primary sites, applying third-order mixing to generate stable frequency outputs. This design ensures continuous operation even in case of single-node failures and efficiently addresses varying user requirements with limited resources. Experimental validation on a 220 km fiber-optic ring network demonstrates frequency instabilities of 2.65 × 10-14 @ 1 s and 4.58 × 10-17 @ 10 000 s at the primary site and 1.48 × 10-14 @ 1 s and 4.02 × 10-16 @ 10 000 s as well as 1.56 × 10-14 @ 1 s and 9.70 × 10-16 @ 10 000 s at two intermediate nodes. The scheme provides a robust foundation for stable frequency distribution in metropolitan fiber-optic networks.