| Fiber-based time and frequency synchronization has the advantages of high accuracy and reliability.More and more scientific research and engineering applications show a significant pickup in demand for it such as high precision atomic clocks comparison,radio interferometry and deep space navigation.This thesis reviewed the development of time and frequency dissemination and synchronization.When applying the existing fiber-based time and frequency synchronization schemes to large-scale fiber networks,some limitations emerge.Aiming at overcoming these limitations,we propose and demonstrate a variety of new synchronization schemes.These schemes may be applied to the Square Kilometre Array(SKA)project.This thesis introduces a frequency synchronization scheme in which the phase-noise compensation function is applied at the client site.Through active phase noise compensation,precise frequency can be recovered.For 50 km fiber spool dissemination,relative frequency stabilities of 3.1×10-14/s and 2.7×10-17/day are obtained.This scheme is suitable for constructing the frequency synchronization networks with star-shaped topology and has been selected as the primary concept for SKA synchronization.This thesis also introduces a fiber-based multiple-access frequency synchronization scheme.The precision frequency can be recovered at arbitrary node along the entire fiber link.Relative frequency stabilities of 2.0×10-14/s and 1.6×10-16/104 s for download reference frequency are obtained.When one frequency dissemination fiber link includes three download sites,relative frequency stabilities are distributed in the range of(2.0 ± 0.3)×10-14/s and(1.8 ± 0.2)×10-16/104 s.With this scheme,the SKA frequency synchronization network will be dramatically simplified.For practical applications,the frequency synchronization system was shipped to SKA South Africa site to perform a trial test.The test gives the performance of the system working on overhead fiber links,the topology specifications and the frequency dissemination stability for long distance dissemination.During the test,we found that the system is sensitive to ambient temperature of fiber link so that the phase fluctuation cannot be completely compensated.Then we optimize the 1f-2f frequency synchronization scheme and perform a comparison test of the original and optimized schemes on 50 km fiber spools.After research on the digital communication mode of commercial optical networks,we propose a scheme that frequency synchronization system can collaborate with switching equipment in optical network.A 30 km+30 km optical network with data exchange is conducted in our lab.A frequency synchronization system on relay mode collaborates with it.Relative frequency stabilities of 4×10-14/s and 2.5×10-16/104 s for recovered frequency are obtained.And frequency synchronization does not impact the performance of data exchange.Furthermore,based on the topological structure of optical communication networks,we also propose the scheme of large scale frequency synchronization network based on existing optical communication networks.Safety and performance of the frequency synchronization network can be improved. |
