IEEE Trans Ultrason Ferroelectr Freq Control. 2022 Feb;69(2):892-901. doi: 10.1109/TUFFC.2021.3134163. Epub 2022 Jan 27.
We perform experiments exploring the use of white rabbit precision time protocol (WR-PTP) for time and frequency dissemination over long-distance optical fiber links. We use unidirectional links, to ensure compatibility with active telecommunication networks, and White Rabbit equipment with modifications for improved performance. Using fiber spools, we realize a 500 km, four-span cascaded white rabbit link. We show short term fractional frequency stability of 2×10 , averaging down to 2×10 at one day of integration time, with no frequency shift within the statistical uncertainty. We demonstrate the impact of increasing the White Rabbit SoftPLL bandwidth and the PTP message rate. We show evidence of the effect of thermal fluctuations acting on the fiber, and finally discuss the limitations of the achieved performance. We show comparisons with experimental data acquired with commercial good quality global positioning system (GPS) receivers and show that the medium- and long- term stability and accuracy are more than one order of magnitude better with a WR-PTP link.
我们进行了实验，探索使用白兔子精密时间协议（WR-PTP）在长距离光纤链路中进行时间和频率分发。我们使用单向链路，以确保与有源电信网络的兼容性，并且使用经过改进以提高性能的 White Rabbit 设备。使用光纤卷轴，我们实现了一个 500 公里、四跨级联的白兔子链路。我们展示了短期分数频率稳定性为 2×10 ，平均达到 2×10 在一天的积分时间内，在统计不确定性内没有频率偏移。我们演示了增加 White Rabbit SoftPLL 带宽和 PTP 消息速率的影响。我们展示了作用在光纤上的热波动的影响的证据，最后讨论了所达到的性能的限制。我们将实验数据与使用商业高质量全球定位系统（GPS）接收器获得的实验数据进行了比较，并表明 WR-PTP 链路的中短期稳定性和准确性要好一个数量级以上。
