基于飞秒光梳的远距离高精度自由空间时频同步技术研究

Time and frequency synchronization based on free-space laser transfer with simple configuration, high precision and anti-electromagnetic interference, has attracted a wide attention. At present, the free-space time-frequency synchronization system with a distance of a few kilometers, can achieve a synchronization resolution at picosecond level. However, this distance and resolution are far away from those of the fiber-based time and frequency synchronization links, which can achieve hundreds kilometers distance and resolution of femtosecond-level. In this research, some unsolved scientific problems in long-distance and high-precision synchronization system by transferring femtosecond optical frequency comb over free-space link will be studied deeply. We will first reveal the mechanism of the timing jitter of the optical pulses transmitted in free-space, and propose the two-way transfer-based jitter elimination scheme; then we will reveal the mechanism of the power attenuation of the optical pulses, and propose optical bi-directional amplifier-based signal relay scheme; next we will reveal the mechanism of the broadening of the optical pulses, and propose the dispersion compensation scheme; lastly we will introduce a discrimination technique with an ultra-high resolution for femtosecond frequency comb. Based on these studies above, we will build a long-distance and high-precision time and frequency synchronization system, and achieve a synchronization experiment over 20 kilometers free-space link with a resolution of sub-picosecond. The achieved distance and resolution with our free-space synchronization technique will fully meet the requirement of the fields where the fiber transmission link is used.

采用自由空间激光信号传输的时频同步技术由于结构简单、精度高、抗电磁干扰能力强等优点受到广泛关注。目前，在千米级距离上自由空间时频同步系统的精度已达到皮秒量级，但该传输距离和同步精度还远低于光纤时频同步技术中百千米级距离和亚皮秒级精度的指标。在本课题中，我们将对采用飞秒光梳实现远距离高精度自由空间时频同步场合下存在的尚未解决的基础科学问题展开深入研究。研究包括：自由空间光梳信号传输中，时延抖动产生机理与时延抖动消除策略研究；自由空间光梳信号传输中，脉冲强度衰减机理与双向光放大中继策略研究；自由空间光梳信号传输中，脉冲时域展宽机理与色散补偿策略研究；飞秒光梳超高精度鉴相技术研究。在完成以上研究内容的基础上，最终实现远距离高精度自由空间时频同步系统，完成传输距离大于20千米、同步精度为亚皮秒量级的同步实验。该自由空间时频同步系统的传输距离和同步精度可满足现有光纤时频同步技术应用场合的需求。

采用自由空间激光信号传输的时频同步技术由于结构简单、精度高、抗电磁干扰能力强等优点受到广泛关注。目前，在千米级距离上自由空间时频同步系统的精度已达到皮秒量级，但该传输距离和同步精度还远低于光纤时频同步技术中百千米级距离和亚皮秒级精度的指标。在本课题中，我们对采用飞秒光梳实现远距离高精度自由空间时频同步场合下存在的尚未解决的基础科学问题展开了深入研究。研究包括：自由空间光梳信号传输中，时延抖动产生机理与时延抖动消除策略研究；自由空间光梳信号传输中，脉冲强度衰减机理与双向光放大中继策略研究；自由空间光梳信号传输中，脉冲时域展宽机理与色散补偿策略研究；飞秒光梳超高精度鉴相技术研究。在完成以上研究内容的基础上，最终实现远距离高精度自由空间时频同步系统，完成了传输距离千米、同步精度为亚皮秒量级的同步实验；完成了传输距离20千米、同步精度为皮秒量级的模拟同步实验。该自由空间时频同步系统的传输距离和同步精度可满足现有替代光纤时频同步技术应用场合的需求。