Research On High Precision Time Signal Generator And Relay Based On Optical Fiber Time Synchronization System

With the rapid development of technologies such as communication,positioning and navigation,deep space exploration and aerospace,many fields have put forward higher requirements for high-precision time synchronization technology.The traditional system based on satellite twoway time-frequency transmission or global positioning system commonview method can no longer meet the current time synchronization needs;and the optical fiber system has the advantages of cost and accuracy,which promotes the rapid development of long-distance optical fiber time transfer system.With the increase of the transmission distance of the optical fiber time synchronization system and the improvement of the time synchronization accuracy,the performance of the high-precision time signal has become one of the factors restricting the development of the time synchronization system.Therefore,the research on the generation and relay of the high-precision time signal is of great significance and value.Against the above background,the research contents of this paper are as follows:1.In order to meet the special requirements of the ultra-longdistance optical fiber time synchronization system for the relay module,a high-precision pulse relay module based on the monostable trigger and the avalanche triode pulse generation circuit is designed and implemented.The phase demodulation scheme adopted by the optical receiver of the optical fiber time synchronization system makes the singlepeak pulse signal into double-peak pulses separated by several nanoseconds;if the amplifier is directly used as a relay,the number of pulses will increase after multiple relays.It will deteriorate the transmission environment and even interfere with the judgment of the time interval counter;therefore,a monostable flip-flop is used in the relay module to combine the double-peak pulses,and then high-precision pulses are generated by the avalanche triode-based pulse generation module.After experimental tests,the negative pulse output by the high-precision pulse relay module has a width of 5 ns,a falling edge of 280 ps,and a time stability of 10.423 ps.In the laboratory back-to-back optical fiber time synchronization system,the measured time stability of the system is 24.229 ps.2.In order to meet the delay accuracy and stability of the delay pulse generator in the optical fiber time synchronization system,a high-precision delay pulse generator based on FPGA(Field Programmable Gate Array)and programmable delay line chip is designed and implemented.The pulse generator takes the rubidium clock of 10 MHz as the clock source,and the phase-locked loop multiplies it to 200 MHz as the system clock;the system clock is transmitted to the fine delay module with the delay line chip as the core through the FPGA,and then transmitted back The FPGA completes the processing of the coarse delay,and finally the FPGA outputs a second pulse signal with a pulse width of 200 ns.The host controls these two delay functions through serial communication.The experimental test shows that the high-precision pulse generator can achieve a fine delay with a resolution of 5 ps and a coarse delay with a resolution of 5 ns,and the time stability of the output pulse signal is less than 30 ps.