Time Interval Measurement Based on Fine-Time Synthesis Module

The time-to-digital converter (TDC) is a key technology for achieving accurate time delay measurements in fiber-optic time transmission and synchronization system. Current architectures for TDC implementation mainly consist of coarse counters paired with different fine counter architectures. Here, we propose and implement a new fine counter architecture that synthesizes the time interval between pulses and the reference clock into a single pulse. The width of synthesized pulse is measured to enhance precision through the reuse of measurement units. The TDC stability is evaluated through the back-to-back (BTB) experiment. The short-term time deviation (TDEV) is 8.07 ps@1s, and the long-term TDEV is $0.18 \text{ps}{@}10^{4}\mathrm{s}$. Additionally, the proposed TDC is applied in a laboratory-built round-trip time synchronization system over 680km fiber link. The timing jitter of the system is measured to be 38.02ps.