中文摘要：

针对目前基于数字同步体系（SDH）网络的长距离时频同步精度不高、不易与现有网络相融合等问题,提出了一种采用桥接测量方式拓展SDH网络无源双向比对授时距离的新方法。分析了桥接测量法的中间站时延测量误差。搭建了220km的4节点SDH实验网络,通过桥接测量法跨越两个SDH网元设备,利用桥接站时延数据的测量结果对终端时钟实施伺服控制,使其跟踪于主站时钟。授时系统的同步误差峰-峰值为965ps,均方差为117.7ps。实验结果表明,使用桥接测量和时钟伺服技术不但能有效拓展授时距离,而且能在SDH网络终端再生与基准时钟高度同步的时间频率信号,达到较高的授时精度水平。

英文摘要：

According to the problem that the precision of time transfer over long-distance fiber based on synchronous digital hierarchy （SDH） optical network is not high and it is difficult to adapt to present SDH optical network, a new technique of two-way time transfer with passive listening and extending transfer distance based on SDH optical network has been proposed. Basic principle of the bridged tech- nique of extending transfer distance has been given. The errors brought by the measurement of bridged equipments and comparison of frame header have been analyzed. The experiment on 220 km optical fiber including 4 SDH equipments in the laboratory has been realized. By using bridge techniques, two SDH e- quipments are went across. Meanwhile, the time delay data from bridged equipments has been used for servo control every second. Therefore the clock at remote station keeps tracking the clock at source sta- tion. The peak - to - peak value of synchronization error of this system is 965 ps. The rms - difference is 117.7 ps. The results of experiment show that the bridge and servo technology is useful for extending transfer distance. It is a feasible way for regenerating highly synchronized time at remote station. Also, the precision of time transfer has reached a high level in the experiment.