High-precision time–frequency synchronization in Ethernet communication networks

Abstract

Currently, many applications require not only high-speed communication, but also high-precision time–frequency synchronization. However, the simultaneous transmission and exchange of digital time signals with continuous analog frequency signals face challenges in large-scale Ethernet networks. Here we report a method to converge high-precision time–frequency synchronization and communication in fiber-optic distributed Ethernet networks. The time–frequency signals are multiplexed by wavelength division to the communication data with different optical wavelengths. The transmission error of the time–frequency signals was measured and controlled using a round-trip method. Network switching is implemented by add-drop multiplexing with a continuous wavelength selector switch and IP packets for the frequency signal and communication data, respectively. Experimental verification is carried out in a five-node network. In this network, high-precision time–frequency synchronization in Ethernet communication networks is realized. The frequency instability is less than 3 × 10−14@1 s, and the time synchronization offset is less than 70 ps with the communication rate of 1.25 Gbps. These results demonstrate the broad application prospects of the proposed method in distributed coherent detection fields with multiple nodes.