Design And Implementation Of An Uninterrupted Distributed Fiber-Optic Time Transfer System

Time bases are extremely important for scientific research(such as time frequency measurement,aerospace and basic physical measurement)and socio-economic development(such as satellite navigation,telemedicine and high-speed communications).Due to the advantages of low loss,high speed,high stability,anti-electromagnetic interference and so on,the optical fiber networks has been around the world.In recent years,fiber-based point-topoint time transfer technology has also made a number of breaking advances in long range and high accuracy.However,in many practical applications,such as distributed base station technology,distributed radar technology and time-frequency benchmarking between countries,a one-to-many time transfer is required,that is,a distributed time delivery solution.In this thesis,we design a synchronous TDMA based time transfer scheme over a branching fiber-optic networks to meet the demand of the development of point-to-multipoint high-precision optical fiber time-transfer technology.aiming at its core problem,this paper designs an uninterrupted point-tomultipoint distributed one-way,two-way,same-fiber and same-time transmission system based on TDMA mechanism.The main work of this thesis includes:(1)The existing typical distributed optical fiber time delivery scheme is introduced,and the characteristics,advantages and disadvantages of each scheme are compared and analyzed.(2)The basic theories of this synchronous TDMA based distributed time transfer system such as system metrics,noise source analysis and asymmetric source analysis are analyzed.(3)The synchronous TDMA based time transfer system is designed and described in detail which includes scheme design,working principle,workflow,hardware and software modules of the system.(4)A 1×8 experimental system with a 50 km single-mode fiber in each sub-path is demonstrated.Experimental results show that the stabilities of less than 40 ps/s and 10 ps/d can be achieved and the calculated combined uncertainty is not beyond 51.5 ps,which agree well with our experimental expectation.