The Research On Fiber-based Time And Frequency Dissemination And Sychronization Technique

High precise time and frequency dissemination is of major importance for many sci-entific applications in areas such as comparison of frequency standards,radio astronomy,and deep space detection.With its advantages of low attenuation,high reliability,and continuous availability,the existing fiber optic network has become an attractive option for use in such ultrahigh precision applications.Considering the limited accessibility of the point-to-point work mode of fiber link,this paper introduces fiber-based time and fre-quency schemes which are appropriate for network-based applications.What'more,the applications of time and frequency dissemination technology on radio interferometry and navigation positioning are also discussed and analyzed.This paper will mainly introduce the several following works.1.A fiber-based,multiple access timing signal synchronization scheme is demon-strated.A highly stable timing signal can be recovered at arbitrary points along the fiber link with the help of this scheme.The experiment is carried out on 30 km fiber spools placed in a temperature controlled box.When the temperature fluctuation is about 30^?C,the fluctuations of the stabilized timing signals from the remote and download sites are only±100 ps and±125 ps respectively.After the calibration of system error caused by transmission path asymmetry and thermal drift,a 100 ps magnitude synchronization accuracy is realized.This method could provide new insights into the construction of a large scale fiber-based time and frequency transfer network.2.A fiber-based,star-shaped joint time and frequency dissemination scheme is demonstrated.By working in cooperation with the existing commercial telecommuni-cation network,our scheme enables the integration of frequency,time and digital data networks and could represent an ideal option for interconnection among scientific in-stitutions.When the temperature fluctuation is about 30^?C/day,±50 ps timing signal stability and 3×10^-14/s frequency signal stability at receiving site are realized.The proposed scheme offers an attractive option for the construction of large-scale fiber-based frequency and time transfer networks.It has the potential to play a great role in national defense industry or other common applications.3.This paper also introduces two examples of high precision time and frequency syn-chronization technique being applied to areas such as radio interferometry and navigation positioning.The star-shaped frequency synchronization scheme proposed by Tsinghua University is promising for Square Kilometer Array?SKA?frequency transfer applica-tion.In fact,it has already been selected as the primary concept for SKA synchronization network.The second example is the feasibility test and discussion about the possibility of the Tsinghua University free space frequency dissemination scheme being applied to the ground-to-satellite frequency transfer link in the future.As a member in the test team,the writer take an active part in these two field trials.