作为第四代同步辐射光源，高能同步辐射光源对束流轨道稳定性提出了极高的要求，即在500 Hz左右带宽范围内，储存环中束流轨道的水平和垂直方向稳定度要优于该方向束团均方根尺寸的10%。为实现上述目标，快速轨道反馈系统的延时要尽可能低。快速轨道反馈系统将束流位置监测器（BPM）数据从BPM电子学接收并分发至所有子站，其数据传输延时是系统的主要延时。对此，设计并实现了一种基于高性能现场可编程逻辑门阵列（FPGA）和高速收发技术的数据分发方案，来满足快速轨道反馈系统的低延时和高带宽的需求。经过验证平台的搭建与测试，系统数据分发总延时小于10 μs，且24 h内未出现误码，满足高能同步辐射光源快速轨道反馈系统的需求。

FERMI, the seeded free electron laser (FEL) in operation in Italy, is providing the User Community with unique fully coherent radiation, in the wavelength range 100–4 nm. FERMI is the first FEL fully synchronized by means of optical fibers. The optical timing system ensures an ultra-stable phase reference to its distributed clients. Several femtosecond longitudinal diagnostics verify the achieved performance; the bunch length monitor (BLM) and the bunch arrival monitor (BAM) will be presented in this paper. Feedback systems play a crucial role to guarantee the needed longterm electron beam stability. A real-time infrastructure allows shot-to-shot communication between front-end computers and the servers. Orbit feedbacks are useful in machine tuning, whereas longitudinal feedbacks control electron energy, compression and arrival time. A flexible software framework allows a rapid implementation of heterogeneous multiinput–multi-output (MIMO) longitudinal loops simply by selecting the appropriate sensors and actuators.They also acknowledge all funding sources that made the FERMI construction and operation possible, among others: the Italian Minister of University and Research (MIUR),the Regione Autonoma Friuli Venezia Giulia, the European Investment Bank (EIB), the European Research Council (ERC) and the European Commission (EC).