Precise time underpins critical infrastructure in modern society, including telecommunications, computer networks, electrical power grids and broadcasting. At present, Global Navigation Satellite Systems (GNSS) provide the timing signals that are used by these applications; however, time signals delivered over fibre links can offer higher performance. The high accuracy time transfer achievable by fibre is important for synchronising clocks in high-end scientific research projects such as particle accelerators and radio telescope arrays. In addition, distributing time over an optical fibre directly from a timing institute can provide resiliency, accuracy and traceability to the international time scale Coordinated Universal Time (UTC). These are key requirements for timing in industry and commerce, and in applications such as the timestamping of financial trades, fibre distribution offers a secure alternative to time from GNSS. This article will present techniques for distributing time by fibre that are commercially available and widely used for applications in industry, science and metrology.

精确的时间支撑着现代社会的关键基础设施，包括电信、计算机网络、电网和广播。目前，全球导航卫星系统 (GNSS) 提供这些应用程序使用的授时信号；然而，通过光纤链路传送的时间信号可以提供更高的性能。光纤可实现的高精度时间传输对于粒子加速器和射电望远镜阵列等高端科学研究项目中的时钟同步非常重要。此外，直接从计时机构通过光纤分配时间可以提供对国际时标协调世界时 (UTC) 的弹性、准确性和可追溯性。这些是工商业时间的关键要求，在金融交易时间戳等应用中，光纤分布提供了一种安全的替代 GNSS 时间的方法。本文将介绍通过光纤分配时间的技术，这些技术在商业上可用并广泛用于工业、科学和计量学。