High-Precision Fiber-Optic Time Transfer System Based on Bidirectional FDM and Correlation Processing

SummaryWe report on a high-precision fiber-optic time transfer system over single optical fiber utilizing the same wavelength in both directions based on bidirectional frequency division multiplexing and cross correlation processing (BFDM-CR). The probe signals and the backscattering noises are effectively discriminated by electrical bandpass filtering for the non-overlapping spectrum of the bidirectional transmission signals. In this way, the impact of the Rayleigh backscattering and the dispersion-induced symmetric deviation over fiber link can be suppressed at the same time. The time interval of the received signals and the local signals is obtained by cross correlation processing to improve the SNR of the measurement on the time interval. A time transfer system based on BFDM-CR over 50km fiber-link is experimentally demonstrated. The stabilities in terms of time deviation (TDEV) are less than 19.2 ps/s and 2.2 ps/10000s, respectively.