| 题名 | 单频光纤激光器及光纤时频传递技术研究 |
| 作者 | 杨飞 |
| 学位类别 | 博士 |
| 答辩日期 | 2013 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 蔡海文 |
| 关键词 | 单频光纤激光器 光纤时频传递 保偏光纤光栅 噪声 线宽 |
| 其他题名 | Studies on Single-frequency Fiber Laser and Fiber-optic Joint Time and Frequency Transfer |
| 中文摘要 | 低噪声窄线宽单频光纤激光器在相干激光雷达、相干光通信、高精度光纤传感、引力波探测等领域具有重要的应用前景；高精度光纤时频传递技术在时钟基准比对、甚长基线干涉(VLBI)、深空探测、卫星导航定位等领域也具有广泛的应用前景，总体看来前者是利用光纤产生低噪声激光，后者是利用光纤传递高精度时频信息，两者在噪声特性等本质方面具有诸多共同特征。基于这样的背景，本文以噪声的特性、表征测量、补偿抑制为线索开展了单频光纤激光器和光纤时频传递技术的研究，研究内容贯穿元件、器件、系统三个层次，主要涉及保偏光纤光栅的制备及特性研究、低噪声窄线宽高功率单频光纤激光器、高精度光纤时频同时传递系统以及它们对应的特性表征测试系统的研制和实验研究，还对多个特定物理问题和现象进行了理论分析和建模以及数值模拟。 本文的主要研究内容和结果包括： 1. 首次在实验上观察到保偏光纤光栅微弱的中间峰交叉偏振模式耦合现象，并从Helmholtz方程出发考虑新的实验条件重新推导了新的耦合模方程，克服了传统耦合模方程在处理该问题时不自洽的问题，对该现象给出了完整合理的理论解释。所得结论不仅描述了保偏光纤光栅一种新的耦合机制，而且对它的实际使用具有重要的指导意义。 2. 在对增益介质存在双折射缺陷时的线型腔光纤激光器偏振输出特性建模分析时提出将谐振腔的偏振模式起振情况和输出偏振态分开考虑，即先利用谐振腔Jones矩阵和谐振条件描述偏振模式起振特性，然后再利用等效波片模型分析输出激光的偏振特性，得出谐振腔增益介质双折射主轴必须与保偏光纤光栅的主轴平行或正交，方可得到高消光比的线偏振输出。同时对该结论进行了实验验证。 3. 在上述对保偏光纤光栅和谐振腔偏振特性充分研究的基础上，利用单模光纤，波长、带宽和反射率均匹配的窄带保偏光纤光栅对、高增益Er/Yb共掺磷酸盐玻璃光纤搭建了窄线宽的单频光纤激光器。获得了输出功率大于100 mW，线宽4.2 kHz，偏振消光比大于40 dB的单频激光输出，其中偏振消光比是该领域迄今文献报道的最高值。 4. 从电磁场方程的基本形式出发阐述了激光、微波时频源和光纤时频传递各自噪声特性的物理量，并用统一的数学手段进行了定义，使得对光学振荡器及其输出激光噪声的描述和对微波振荡器及其输出时频信号噪声的描述得到了一致的理解和表述，使得将利用光纤产生低噪声激光和利用光纤传递高精度时频信息这两个本不相干的领域进行统一的研究成为可能。同时对特性参数搭建了对应的测试系统，包括激光强度和相位噪声测试、微波频率相位噪声测试、秒脉冲时间抖动测试等。 5. 对单频激光器的强度噪声特性进行了理论模拟和实验研究，并利用光电负反馈对强度噪声中的弛豫振荡进行了完全抑制，利用往返EDFA对低频噪声进行了抑制，使得激光器在10 Hz处的强度噪声为-120 dB/Hz，大于100 kHz时为-130 dB/Hz，接近所用探测器散粒噪声极限。也对单频激光器的频率噪声特性进行了研究，特别利用边频锁定的方式将激光输出频率稳定到了温控隔振隔音的窄带光纤Bragg光栅的斜边上从而对激光器的频率波动进行了抑制，激光器在1 Hz处的频率噪声为500 Hz/√Hz，100 s频率稳定度为7×10-10。 6. 从微波信号在光纤中传输的延迟相位方程出发，建立了光纤时频传递噪声来源分析模型，分别研究了温度、色散、强度噪声等各因素的影响，所得结论经过了实验验证，对光纤时频传递系统的设计和实现起到了重要的指导作用。 7. 提出了一种高精度光纤时频同时传递方案，即利用波分复用/解复用方式进行时频同时调制解调，利用双向双波长还回与本地信号拍频鉴相的方式获取误差信号并消除中途反射信号的影响，利用快慢变串级PID分别控制快速小范围和慢速大范围的压控光纤延迟线从而在光域对噪声进行补偿。根据该方案搭建了实验系统，并利用北京某3个通信机房之间的实地光纤链路进行了现场试验。即在60 km距离上对氢钟的时频信号进行同时传递，实现了100 MHz频率信号和秒脉冲时间信号的较长距离直接同时传递，其中100 MHz频率信号的天稳定度达到6.9×10-18，秒脉冲时间信号的均方根抖动为23.3 ps。 |
| 英文摘要 | Single-frequency fiber laser with low noise and narrow linewidth has widespread application in lidar, coherent communication, high-accuracy fiber sensing, gravitational wave detecting, etc. High-accuracy fiber-optic joint time and frequency transfer (FTFT) has widespread application in comparision between standard clock, very long baseline interferometry(VLBI), deep space network, navigation, etc. The former produces laser with low noise in optical fiber, and the latter transfers the high-accuracy time and frequency signal by using of fiber optic. They have many same characters such as noise. Based on such background, the research on single-frequency fiber laser and FTFT are carried out in terms of characterization, measurement and compensation of noise. Research contents involve element, device and system. They include the writing and characters of polarization-maintaining fiber Bragg grating (PM-FBG), single-frequency fiber laser with low noise, narrow linewidth and high power, high-accuracy FTFT system and their performance test systems. They also include the theory analysis and numerical simulations for many physical problems and phenomena.The main contents of the thesis are as follows: 1. A weak resonant peak at the middle of two orthogonal polarization modes in PM-FBG is found in experiment. A new coupled mode equation (CME) from Helmholtz equation is built to eaplain the phenomenon completely. And it overcomes the problem of the traditional CME being not self-consistent when describe the phenomenon. The results not only describe a new cross coupling mechanism of PM-FBG, but also have important guiding significance for its actual application. 2. The idea of analysis spearately for resonant situation of polarization eign modes and output polarization of the linear cavity laser is proposed. The resonant situation is analyzed by employing transmission matrix and resonance conditions. And the output polarization is analyzed with a wave plate model. The main result is that the high polarization extinction ratio (PER) output laser can be achived when the major birefringence axes of the active fiber are parallel or orthogonal with the major axes of the PM-FBG. The result is verified by experiments. 3. Base on the above research results about PM-FBG and polarization characters of laser cavity, a narrow linewidth fiber laser is fabricated by using of single-mode fiber, a pair of narrow band PM-FBG matching with wavelength bandwith and reflectivity, high gain Er/Yb co-doped phosphate glass fiber. The output power of the laser is more than 100 mW, the laser linewidth is about 4.2 kHz, and the PER is more than 40.5 dB. And the PER is the highest value in reported results of the fields to my knowledge. 4. The physical quantities of noise characters of laser, microwave time and frequency signal and FTFT are described from the basic form of electric-magnetic field equations and defined by uniform mathmatical forms. Then the laser noise and time and frequency signal noise could be understood consistently. And studying the laser and FTFT together is feasible. The noise test systems which include laser noise, microwave frequency signal noise and time signal fluctuaion are fabricated. 5. The intensity noise of laser is studied theoritically and experimentally. The relaxation oscillation is suppressed by photoelectric negative feedback. And the low frequency noise is reduced by the roundtrip EDFA. The RIN reaches -120 dB/Hz@10 Hz, -130 dB/Hz@>100 kHz, which are close to the shot noise limit of the used photodetector. The freuqency noise of laser is investigated experimentally. Its frequency is locked to a narrow band FBG in the state of temperature control, sound insulation and vibration isolation. The freuqency noise is 500 Hz/√Hz@1 Hz, and the fractional frequency stability is 7×10-10@100 s. 6. The analytic model about noise source of FTFT is induced from the phase delay eaquation of microwave in fiber optic.The influence of temperature, dispersion, intensity noise and other factors are studied respectively. The results are verified by experiments, and make important guiding role in the design of FTFT system. 7. A high-accuracy FTFT scheme is proposed. The time and frequency joint modulation is realized by wavelength division multiplex. The error signal is got from the beat of the two-way back signal through single-fiber and local reference signal. The noise is compensated by optical methods with the use of fast small range and slow large range fiber-optic delay lines which are controlled by fast and slow PID respectively. The experimental system is realized based on the scheme and the field tests are conducted in the dark fiber link connecting 3 communication rooms in Beijing. The field experiment is joint time and frequency signals from Hydrogen clock transfer in 60 km link. The day stability of 100 MHz frequency signal reaches 6.9×10-18, and the RMS jitter of 1 pps time signal is 23.3 ps. |
| 语种 | 中文 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15730]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 杨飞. 单频光纤激光器及光纤时频传递技术研究[D]. 中国科学院上海光学精密机械研究所. 2013. |
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