Ultra-precise timing has become a prerequisite for many modern large-scale scientific instruments, and timing precision is a crucial enabling factor to achieve the ultimate goals of those instruments. Here, we review the recent progress in timing technologies, including timing characterization methods among different kinds of sources (optical lasers, microwaves and x-ray pulses), large-scale free-space timing synchronization, and fiber-based timing synchronization. Technical and fundamental limitations of fiber-based timing systems are also discussed to provide future directions.

中文翻译：

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大型科学仪器的超精确定时和同步

超精密定时已成为许多现代大型科学仪器的先决条件，而定时精度是实现这些仪器最终目标的关键使能因素。在这里，我们回顾了计时技术的最新进展，包括不同种类的光源（光学激光器，微波和X射线脉冲）之间的计时表征方法，大规模自由空间计时同步和基于光纤的计时同步。还讨论了基于光纤的计时系统的技术和基本局限性，以提供未来的方向。