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高精度光纤时间传递技术
其他题名Accurate Time Transfer over Optical Fibers
程楠
学位类型博士
导师蔡海文
2016
学位授予单位中国科学院上海光学精密机械研究所
关键词光纤时频传递 时间同步 偏置点控制 时间间隔测量 伪随机码
摘要高精度时频传递系统在深空探测、甚长基线干涉(VLBI)和计量学等领域有非常重要的应用。基于卫星的时频传递系统,例如全球卫星定位系统和卫星双向时频比对,它们的时频传递精度已经不能满足这些领域中越来越高的应用需求。而光纤的高带宽、低损耗和抗干扰等特性,使其成为一种新的时频传递的介质,并受到研究人员的关注。基于光纤的时频传递精度也获得了显著地提高。在许多应用领域,例如甚长基线干涉,深空探测和导航等领域,多基站的时钟同步是一种基本应用需求。这需要准确地获得两地之间的信号传输时延,而单一的频率传递系统无法满足这一需求。因此光纤时间频率同时传递系统越来越受到学者的关注,并在近些年得到了迅速的发展。与频率信号相似,时间信号在光纤中传递的过程中,同样受到光纤周围环境温度和振动的影响,因此在时间传递的过程中同样需要补偿传输时延的波动。 本文面向光纤时间频率同时传递的应用需求,针对时频同时传递系统存在的时频信号的串扰、时频信号的同时补偿等问题提出了基于波分复用和光学补偿技术的时间频率同时传递系统,主要的研究内容如下: 1. 提出了基于波分复用和光学补偿的时频传递系统,并实验验证了系统的传递性能。该系统本地频率传递稳定度达到1.7×10-14@1 s,7.1×10-18@104 s。远地频率频率传递稳定度为1.8x10-14@1 s,2.0×10-17@104 s;对于传递的时间信号来说,平均时间400 s后,本地还回的时间信号的稳定度达到了2.6 ps,远地端的时间信号稳定度达到了1.3 ps。 2. 针对时频传递系统中的时间同步需求,提出了时间同步理论和时间同步校准方案,并进行了实验验证。实验结果证明,两地的时间信号同步精度可以达到1.6 ps。 3. 研制了应用于秒脉冲(1 PPS)传递的电光调制器偏置点控制系统,将调制器的偏置点控制在传输曲线的最低点和正斜率正交点之间,通过测量1 PPS信号的低电平电压值的波动情况来反馈控制调制器的偏置点。实验验证,当1 PPS传输稳定度在平均时间1 s时,时间稳定度为 17 ps,在平均时间为104 s时,时间稳定度为1.7 ps。该系统稳定性优于商用微扰法的偏置控制系统。 4. 研制了基于TDC-GPX芯片的精密时延测量系统,并研究了40 MHz外接高稳定时钟系统,对该时延测量系统进行了系统性能验证,实验证明该系统时延测量分辨率可以达到10 ps,测量精度优于100 ps。 5. 研制了光纤时频传递系统的工程样机,并在北京某处的城市光纤网络中实现了三点的时频同步,将中心站氢钟的10MHz频率信号和1PPS信号传递到两个光纤距离为14km和110km的远地站点。实验中,14km链路经过补偿之后的频率稳定度为3.0×10-14 @1 s,1.4×10-17 @104 s,与此同时,110km链路的频率稳定度经过补偿之后达到8.3×10-14@1 s,1.7×10-17 @104 s。两条链路1 PPS往返传递的时间稳定度在平均时间为1000 s时达到了 6.9 ps。实验中还进行了时间信号同步实验,理论计算两个远地端与本地的时间同步精度分别达到了12.3 ps (14 km)和 13.1 ps(110km)。最后,通过搬运钟实验验证的时频同步性能。 6. 在苏州、无锡和常州三地280 km的光纤链路中进行了目前国内已知最长距离的射频时频同传实验。实际测试中,远地端频率传递稳定度达到了4.0×10-14@1 s,7.3×10-18 @105 s,本次实验准确地验证了远地端的时间同步精度达到了28 ps。 7. 对基于伪随机码扩频传输的时间信号传递系统进行了调研,并进行初步验证实验,提出了基于伪随机码的光纤信号传递时延测量系统。实验结果表明,基于模拟低通滤波方案的时延测量系统的时延测量精度可以达到1 ps。
其他摘要The Precise time and frequency signal dissemination has significant application in scientific researches such as very long baseline interferometry (VLBI), deep space network (DSN) and metrology. The accuracy of satellite-based time and frequency transfer systems, such as GPS and two-way satellite time and frequency transfer (TWSTF), is insufficient to develop these applications further. Due to high bandwidth, low attenuation and resistance to external interference, Optical fiber has become an attractive alternative to satellite links, offering much improved accuracy. In many applications, such as VLBI, DSN and navigation, the synchronization of clocks in different locations is a basic requirement. The exact propagation delay of the time signal between local and remote locations should be obtained. Frequency dissemination alone cannot meet these applications. Joint dissemination of the time and frequency signals and synchronization via fiber networks are widely proposed and demonstrated in recent years. Compared with frequency signal dissemination over via fiber, the time signal also displays fluctuations of the propagation time delay caused by the influence of temperature and vibration. It is necessary to acquire the delay fluctuation and to compensate it actively. In view of the application requirement of the joint time and frequency transfer application requirement, and in consideration of the time- frequency crosstalk and the compensation of the two signals, a precise time and frequency dissemination system based on DWDM and optical compensation is demonstrated in this thesis. The main contents are as follows: 1. In consideration of the time synchronization, a time calibration and synchronization technique for joint time and frequency transfer via optical fiber is described. The verification experiment is achieved via 50 km optical fiber spool in the laboratory, which the accuracy of time synchronization is 1.6 ps. 2. A time and frequency dissemination system based on DWDM and optical compensation is described. The system is experimentally examined via the 110 km spooled fiber in the laboratory. The experimental results showed that the frequency stability of the user end with compensation is 1.8x10-14 at 1 s and 2.0×10-17 at 104 s averaging time, whereas the frequency stability of the local site is 1.7×10-14 at 1 s and 7.1×10-18 at 104 s averaging time. The stability of the one pulse per second (1PPS) at the remote site for the averaging time of 400 s decreases to 1.3 ps, whereas the time stability of 1PPS coming back from the remote site for the averaging time of 400 s decreases to 2.6 ps. The calculated uncertainty of time synchronization is 13.1 ps, whereas the direct measurement of the uncertainty is 12 ps. 3. A bias point control system of Mach-Zehnder modulator (MZM) for transferring 1PPS, which is used in time and frequency transfer via optical fiber. The low-level voltage of the 1PPS output by photodiode is used to measure the drift of the bias point. The measured signal is digital processed and used to control the feedback system to stabilize the bias point. The experimental results show that the time stability of the 1PPS is 17 ps for the averaging time of 1 s, and 1.7 ps at the averaging time of 104 s. Compared with the commercial bias point stabilized system based on dither method. the behavior of our system is more stable, 4. A accurately time interval counter based on TDC-GPX and the external clock of 40MHz are described. The experimental results show that the resolution is 10ps, and the accuracy of the counter is better than 100 ps. 5. The prototype of the fiber-optic joint time and frequency transfer is demonstrated in this thesis. And the system is disseminate two 1PPS signals and one frequency signal (10 MHz) of hydrogen maser from the central location to two remote locations, as far away as 14 km and 110 km, via a metropolitan fiber network in Beijing. The frequency stability of 14 km link reaches 3.0x10-14 averaged in 1 s and 1.4×10-17 in 104 s; and the stability of 110 km link is 8.3×10-14 and 1.7×10-17, respectively. Time stability of two links for the averaging time of 1000 s decreases to 6.9 ps. The time signals at the three locations are synchronized with each other. The accuracies of synchronization are estimated to be 12.3 ps for the 14 km link and 13.1 ps for the 110 km link. Finally, we carry the atom clock among the three stations to verify the accuracy of the time synchronization. 6. We demonstrate a time and frequency signal dissemination and time synchronization system based on the 280 km metropolitan fiber network among Su Zhou, Wu Xi and Chang Zhou. As we know, it is the China’s longest distance fiber based radio joint time and frequency transfer. The frequency stability of 14 km link reaches 4.0×10-14 averaged in 1 s and 7.3×10-18 in 105 s. The accuracy of synchronization is 28 ps. 7. Time transfer by using spread spectrum technology based on pseudo-noise code is investigated, and the preliminary examination is described in this thesis. The fiber-optic time delay measurement system based pseudo-noise code is demonstrated. In the experiment, the accuracy of the time delay measurement is 1ps by using the analogue low-pass filter technology.
语种中文
文献类型学位论文
条目标识符http://ir.siom.ac.cn/handle/181231/15946
专题学位论文
推荐引用方式
GB/T 7714
程楠. 高精度光纤时间传递技术[D]. 中国科学院上海光学精密机械研究所,2016.
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