Research And Design Of Timing Calibration System For QKD Photon Based On FPGA

With the development of quantum theory and technology,quantum secure communication based on quantum key distribution(QKD)has gradually become a powerful technical means to guarantee the security of network information.In the national government,army,finance,energy,scientific research and other information security field has a wide range of applications.Timing calibration of various photons in QKD terminal equipment is a prerequisite for QKD system to generate secure and reliable key,therefore,the research of high efficiency,high precision timing calibration device is important for the security of quantum communication,it can accelerate the process of quantum communication industrialization.Aiming at the problem that there were inherent time deviations among eight channel quantum state signals which at the exit of the QKD equipment,in this dissertation,timing calibration system of QKD photons with high precision time digital converter(TDC)as the core and FPGA as the main control unit was designed.The whole system can be divided into signal conditioning,time measurement and FPGA control module.The signal conditioning module adopted high speed comparator to discriminate the difference small signal,and used the D flip-flop and the RC delay circuit to realize the pulse width,the synchronous photon and the signal photon pulse electric signal was used as the start and stop signals of the TDC,respectively;Time measurement module adopted the high precision time interval measurement chip TDC-GPX to measure the time interval about pulse signal and sent the measurement results to FPGA;FPGA control module was responsible for the control of the external circuit and processing of the measured data,then,the emission time of the eight chaanel signals were adjusted by the delay adjustment instruction,so as to satisfy the eight channel signals indiscernibility in time.In order to verify the performance of the calibration system,the performance of TDC-GPX and QKD photon timing calibration system was tested.The actual test results showed that the measurement precision was less than 80 ps,calibration performance was good by applying to actual QKD devices,it can meet system calibration requirement.