We demonstrate a simultaneous transmission of time-frequency and data over a 160-km urban business network in Shanghai. The signals are transmitted through a cascaded optical link consisting of 48 km and 32 km, which are connected by an optical relay. The metrological signals are inserted into the communication network using dense wavelength division multiplexing. The influence of the interference between different signals has been discussed. The experimental results demonstrate that the radio frequency (RF) instability can reach 2.1×10-14 at 1 s and 2.3×10-17 at 10,000 s, and the time interval transfer of one pulse per second (1 PPS) signal with less than 10 ps at 1 s is obtained. This work paves the way for the widespread dissemination of ultra-stable time and frequency signals over the communication networks.

提出一种相位自校准的光纤微波频率相位传递方案。该方案使用声表面波滤波器的冲激响应的窄带信号作为时间信号，使其与频率信号可同时使用同一波长进行传输。为实现稳定的可重复相位差，利用时间信号的往返传输时延来确定频率信号的整数个周期，并在多次重启的情况下验证了系统相位的稳定性。在60 km实验室平台上对所提方案进行验证，频率传递的稳定度优于4×10-14@1s，5×10-17@10000s。系统多次重启的情况下，所获得的平均相位差最大不一致的峰峰值为0.008 rad，对应于整个周期的0.15%，可保证较高的相位一致性。

相比于传统基于声纳、光缆的水下频率传递技术，水下激光频率传递技术具有更高的灵活性。本文首先介绍了水下激光频率传递技术的背景与意义，同时简要展示了国内外科研机构在水下激光频率传递方面的成果。然后，从理论上描述了水下链路特性的时域和频域特性，前者基于水体折射率微扰，后者基于柯尔莫哥洛夫大气湍流模型。接着，重点报道了电子科技大学在该领域的研究进展，包括电学相位补偿技术、光学相位补偿技术和多址频率分发技术。最后总结了这三类水下频率传递实验，对课题组在水下激光频率传递方面将要进行的工作进行了展望。作为具有较大潜力的水下频率传递技术，未来水下激光频率传递技术将在相关应用中发挥重要作用。

提出了一种噪声抑制方法，设计了基于3×3光纤耦合器迈克尔逊干涉仪的频率传递系统，使用嵌入式系统进行控制，通过调整光纤长度，实时补偿由温度变化等环境因素引起的时延变化，并进行了实验验证。启用时延补偿后，实验用的30 m长传输光纤在环境温度变化21℃条件下长度变化量小于±1 μm，对应时间延迟变化量小于10 fs，所传输的光梳重频信号的频率稳定度没有明显变化。本文工作有望为空间条件下的光钟信号向比对设备的传输路径噪声抑制提供有效的解决方法。

By using a self-reference transfer oscillator method, two individual 1560 nm lasers with about 1.2 GHz frequency difference were phase locked to a 729 nm ultra-stable laser at two preset ratios. By measuring the beat frequency of the two 1560 nm lasers, fractional instabilities of 2×10-17 at 1 s and 2×10-20 at 10,000 s averaging time were obtained, and the relative offset compared with the theoretical value was 4.2×10-21±4.5×10-20. The frequency ratio of them was evaluated to a level of 1.3×10-20 in one day’s data acquisition. This work was a preparation for remote comparison of optical clocks through optical fiber links. The technique can also be used to synthesize ultra-stable lasers at other wavelengths.