为实现准国土范围内高精度授时和守时，利用光纤传递铯钟、氢钟等高精度原子钟的时频信号，在实际光纤链路上验证其长距离传递性能。采用波分复用和双向双波长的传输方法，介绍了在275 km京沪干线上实现高精度时频传递的相关工作。针对长距离光纤链路的特点，探讨了链路损耗与散射、色散与频率噪声、补偿系统动态范围和反馈带宽等对时频传递性能的影响。实验获得了频率信号的秒稳定度达5×10-14和天稳定度达7×10-18的传递性能，同时，千秒尺度下的时间方差可达2.4 ps。

To achieve high precision timing and punctuality in quasi national territory, time and frequency signal of high precision atomic clocks, such as cesium clock or hydrogen maser, is transferred by using fiber to examine the transfer performance of long distance on actual fiber link. By adopting the methods of wavelength division multiplexing and dual wavelength bi-directional transmitting, the related work of achieving high precision time and frequency signal is introduced on 275 km Beijing—Shanghai backbone. Based on the characteristics of long distance fiber link, the impact of loss and scattering of link, dispersion and frequency noise, feedback loop bandwidth and dynamic range of compensating system on time and frequency transfer performance is discussed. Results show that the frequency stabilities are up to 5×10-14 in one second averaging time and 7×10-14 in one day averaging time, and time synchronization stabilities are up to 2.4 ps in one thousand second averaging time.