FAST望远镜天文信号的光传输效率提升机制与性能评测技术研究

Currently, astronomical signal transmission scheme of FAST adopts the “single fiber carrying single channel”, which has the problems of large number of fiber quantity, low transmission efficiency, and heavy line load of cabin-supporting steel cable. In the extension application of FAST, PAF receiver plans to be employed for astronomical survey. In this condition, the number of signal channel is much larger than the fiber resources, and the channel phase stability requirement is also increased significantly. This project aims to perform the studies of dense wavelength division multiplexed (DWDM) astronomical signal optical transmission of FAST, accurate phase compensation, and system performance evaluation techniques under working condition. The project proposes DWDM-based high efficiency transmission schemes of FAST’s astronomical signal, designs accurate phase estimation and compensation method of channel signal under fiber cable movement and environment changes, developing the prototype of DWDM transmission system and channel phase compensation, and performs working condition emulating experiments and field-trial substantiations for the DWDM transmission performances of astronomical signal, overcome the key problems which limiting the further improvement of FAST’s fiber channel transmission efficiency, stability and reliability. The previous study during FAST constructions has solved the signal power stability and durability of fiber cable transmission with large core.number under moving conditions, for the first time worldwide. The project will further develop the DWDM techniques under moving condition, solve the signal phase stability and consistency problem under conditions with large fiber core number, DWDM and cable moving, for the first time.

当前FAST望远镜采用“单芯承载单通道”的信号传输方案，存在光纤数量过多、传输效率低、馈源支撑索线路载荷大的问题。在FAST扩展应用中计划采用相位阵列馈源接收机，通道数量远超当前光纤资源，对各通道相位一致性、稳定性要求显著提高。本项目开展FAST信号的密集波分复用光传输、精确相位补偿和工况条件下的性能评测技术研究，提出基于密集波分复用的FAST通道高效承载方案，设计FAST望远镜通道相位在运动工况下的精确估计和补偿方法，研制密集波分复用传输及通道信号相位补偿样机，并对天文信号的波分复用传输性能进行工况模拟实验和现场测试验证，攻克限制FAST信道传输效率、稳定性和可靠性进一步提升的关键难题。FAST建设过程中在世界范围内首次解决了大芯数运动工况下光缆功率稳定性和抗疲劳问题，本项目将进一步开展光缆运动工况下的密集波分复用技术研究，首次解决大芯数、密集复用和运动工况下的相位稳定及一致性难题。

FAST望远镜馈源舱在跟踪观测过程中以11.6mm/s的速度运动，导致铺设在馈源支撑索上的光缆需不断伸展和弯折，要求光缆中的光电信号在此过程中保持较高程度的功率稳定和长时间的使用寿命。根据设计要求，信号传输用的光缆要能在5年内抗6.6万次拉伸和弯折、信号衰减波动小于0.1dB，指标要求远超仅为1000次、0.2dB的国标、国军标等标准。为解决FAST馈源信号传输条件下的高功率稳定和低损耗问题，国家天文台、烽火通信和北京邮电大学花费4年时间，经过自主研发设计和多次长期工况模拟试验测试，研制成功用于FAST望远镜的48芯动光缆。48芯动光缆经受反复弯曲、卷绕和扭转等机械性能和恶劣自然环境考验，达到了抗10万次弯曲疲劳寿命的世界记录，有效解决了当前FAST望远镜天文信号的在低衰减波动性能要求下的传输可靠性问题。采用“单芯承载单通道”的天文信号传输方案，存在光纤数量过多、传输效率低、馈源舱支撑钢索线路载荷大的问题。. 基于此，本项目开展FAST天文信号的密集波分复用光传输、精确相位补偿和工况条件下的系统性能评测技术开展深入研究，解决限制FAST信道传输利用效率、稳定性和可靠性进一步提升的关键技术难题。通过3年的努力，提出并验证了基于波分复用的天文信号通道相位一致性估计及补偿恢复方法，搭建了基于密集波分复用的FAST动光缆运动工况模拟实验条件，实现了对FAST天文信号经过光缆运动工况条件传输后的幅频响应特性和相频响应特性的准确测量，实验结果表明100波密集波分复用传输系统在动态工况模拟传输条件下补偿后相位偏差小于2mrad，信号功率差异小于0.02dB，在波长数量和传输稳定性上都完成了预定研究任务。对退役动光缆进行了6.6万次弯折实验，全面分析验证运动工况条件下密集波分复用信号的传输性能，评估退役光缆综合性能。 . 项目组发表研究论文14篇：5篇论文在SCI期刊上发表，其中4篇论文发表在Optics Express、Photonics Technology Letters、Journal of Lightwave Technology Letters、Photonics Journal等顶级期刊。申请国家发明专利3项，获授权实用新型专利2项。