Long-Haul Fiber-Optic Time and Frequency Synchronization

SummaryLooking toward future very large telescope arrays and fifth-generation/sixth-generation (B5G/6G) scenarios, building a large-scale fiber-based time and frequency synchronization network will be vital support. To solve the distance limitation caused by dispersion in long-distance frequency dissemination, a chirped fiber Bragg grating (CFBG) enhanced bidirectional erbium-doped fiber amplifier (Bi-EDFA) design is proposed. With this design, frequency dissemination tests are carried out on the 500 km fiber link (50 km-100 km-150 km-100 km-100 km). Stabilities of 1.7×10 ^-14 /s and 6.7×10 ^-18 /10 ⁵ s are obtained. In addition, we apply the concept of time reversal in fiber-optic time synchronization. Owing to time reversal, the clock offset of two sites can be measured without calculating the fiber link delay. Finally, we have carried out the time and frequency integrated synchronization over the 514 km field fiber link. The frequency synchronization stabilities of 2.2×10 ^-14 /s and 2.2×10 ^-17 /10 ⁵ s have been obtained. The time synchronization performance characterized by TDEV of 10 ps at 1 s and 1.2 ps at 10000 s have been realized. ¹