【作者】 徐永钊；

【导师】 任晓敏；

【作者基本信息】 北京邮电大学 ， 电磁场与微波技术， 2007， 博士

【摘要】 本论文的工作是围绕以下项目展开的：以任晓敏教授为首席科学家的国家重点基础研究发展计划（973计划）项目“新一代通信光电子集成器件及光纤的重要工艺创新与基础研究”（项目编号：2003CB314900）；教育部科学技术重大研究项目“基于微结构光纤的新一代光通信器件及系统”（项目编号：104046），国家高技术研究发展计划（863计划）项目“单结构与多结构集成式光子晶体光纤及器件”（项目编号：2003AA311010）以及北京市教委共建项目（项目编号：XK100130437）。光纤在通信系统、传感、医疗器械和各种光学器件等众多领域中具有重要和广泛的应用。在过去的几年里，为了提高光纤在各种应用中的性能，人们积极研制新型的光纤。光子晶体光纤（Photonic Crystal Fiber，简称PCF）的研制成功，是光纤技术领域最新的进展之一，其研究受到了全世界众多研究人员极大的关注。PCF在中心处引入了缺陷作为芯区，而周围排列着许多沿光纤长度方向延伸的空气孔，通过改变空气孔的尺寸和排列方式，可以灵活地控制光纤的传输特性。光纤中微结构的使用使光纤多方面的物理性能得到了改善，并为光纤在各个领域的应用打开了新局面。事实上，每个应用领域也是利用了PCF由于微结构所赋予的优良特性。PCF为光电子器件的设计提供了新的平台，并展示了许多新的功能。它在通信、非线性光学、传感和光纤器件等许多领域中有广阔的应用前景。由于PCF新颖的结构和具有常规阶跃光纤无法比拟的独特特性，PCF在未来可预见的时间里仍将是一个活跃的研究领域。本论文主要对PCF及相关通信光电子技术进行了理论和实验研究，主要研究内容和创新点如下：1．建立了以各向异性完全匹配层（APML）为吸收边界条件的时域有限差分法（FDTD）PCF计算模型，详细讨论了FDTD差分表达式的推导和APML技术，并成功应用于PCF的特性分析。2．提出了改进的有效折射率方法（IEIM）用于精确分析PCF。IEIM由常规的全矢量有效射率方法（EIM）发展而来，但比常规的全矢量EIM方法具有更高的计算精度。IEIM的计算结果无论是与其他方法获得的精确计算结果，还是与先前文献报道的实验结果相比较都非常吻合，是分析PCF一种有力工具。3．提出了利用具有小正常色散值的色散平坦PCF，在通信波段产生宽带、平坦超连续谱的方法。该类型PCF的色散与波长成凸型函数关系，且没有色散零点。采用数值模拟的方法，详细研究了光纤参量和泵浦条件对超连续谱产生的影响。4．设计了具有小正常色散值的色散平坦PCF用于产生宽带、平坦的超连续谱，并通过光谱滤波获得了多波长脉冲信道。5．结合光子晶体光纤和拉锥的优点，设计了一种锥型光子晶体光纤用于产生宽带、平坦的超连续谱。该光纤具有平坦的色散特性，同时色散值沿光纤长度方向逐渐减小，由正值减小到负值。理论研究结果表明，利用该类型的光纤和具有几个皮秒宽度的泵浦脉冲，可以在通信窗口有效地产生平坦的超连续谱。6．首次利用具有小正常色散值的非线性色散平坦PCF和高重复率的皮秒泵浦脉冲，在1.55μm波段产生了谱宽超过90nm的平坦的超连续谱。该宽带、平坦的超连续谱能同时提供波长间隔为10GHz、超过1100路的多波长载波信道。通过对光谱滤波，实验获得了速率为10Gbit／s的多波长脉冲序列。这样的超连续谱源在DWDM光通信系统、波长变换等方面都有重要的应用。同时结合数值模拟的方法进行了研究，模拟结果与实验结果非常一致。7．提出了基于PCF自相位调制效应的全光再生的方案，理论和实验上论证了其可行性。利用PCF和带宽滤波器，获得了近似阶跃状的功率传输函数和没有发生形变的再生脉冲。该再生器对皮秒脉冲起到良好的再生作用，可用于高比特率数据信号的再生。研究结果表明，具有正常色散的非线性PCF适合于全光2R再生。8．提出了利用具有高非线性和大反常色散值的PCF构成的非线性光纤环路镜（PCF-NOLM）进行脉冲压缩和整形的方案。数值结果表明，该方案能高效地压缩脉冲，并能显著抑止压缩脉冲的基座。9．与他人合作，利用PCF实现了对10Gbit／s脉冲信号色散和色散斜率的同时补偿。在C波段的20nm的波长范围内，利用26m的PCF补偿了2km的标准单模光纤的色散。研究结果还表明，该光纤可在从1520nm到1570nm的50nm波长范围内对标准单模光纤的反常色散进行补偿，残余色散可控制在±0.3ps．nm^-1．km^-1之内。10．开展了基于PCF中四波混频效应的全光波长变换的研究。与他人合作，利用30m的色散平坦PCF中的四波混频效应，实现了对10Gbit／s光信号的全光波长变换。平均波长转换效率约为-19.5dB、幅度变化小于±1.4dB、转换带宽达20nm。更多还原

【Abstract】 The research works of this dissertation are supported by the National Basic Research Program of China （973 Project, Grant 2003CB314906）, the Foundation for the Key Program of Ministry of Education of China （Grant 104046）, the National 863 High Technology Project of China （2003AA311010） and the Foundation from the Education Commission of Beijing （Grant XK100130437）.Optical fibers have many important applications, particularly in communication systems, sensors, medical instrumentation, and many kinds of optical components. During the past few years, a great deal of effort has been devoted to the development of new types of optical fibers with the aim of improving the performance of fibers in these applications. Photonic crystal fiber （PCF） is one of the most recent advances in fiber-optic technology that has attracted considerable interest from many researchers around the world. PCFs consist of a central defect region surrounded by multiple air holes that run along the fiber length. By varing the size and pattern of the air holes, the mode propagation properties of the PCFs can be easily controlled. The use of microstructures in optical fibers have opened new developments in various areas of fiber applications, and it is interesting that each of these areas actually takes advantage of different aspects of the enhanced physical performance enabled by the location of microstructures in the fibers. PCFs provide a novel waveguide platform for photonic devices and a number of functionalities have been demonstrated. Those fibers show great potential for various applications in the fields of telecommunications, nonlinear fiber optics, sensor technology and many other novel fiber devices. Because of their novel structure and unique properties that cannot be achieved from conventional step-index fibers, PCFs continue to be an active area of research in the foreseeable future. In this dissertation, PCFs and related optical communication technologies were studied both theoretically and experimentally. The main contents and achievements are as follows. 1. Combinning anisotropic perfectly matched layer （APML） for the boundary treatment, finite-difference time-domain method （FDTD） is introduced to model PCF. The formulations of FDTD and PML techniques are discussed in detail, and this method is successfully used to analyze the properties of PCFs.2. An improved effective index method （IEIM） is proposed for accurate analysis of PCF. IEIM is developed form a conventional fully vectorial EIM and is shown to give more accure results than the conventional one. The results obtaioned by IEIM agree well with accurate numerical results obtained by other methods as well as the previously reported experimental data. IEIM is a powerful tool for analyzing PCFs.3. Dispersion-flattened PCF with small normal dispersion is proposed for generating a flat and broad supercontinuum in the telecommunication band. The chromatic dispersion of the PCF is a convex function of wavelengths and has no zero-dispersion wavelengths over the whole part of the fiber. Numerical simulation is used to study the effect of fiber parameters and pumping conditions on supercontinuum generation in the PCFs.4. Dispersion-flattened PCFs with small normal dispersion are designed for flat broadband supercontinuum generation. Also, multi-wavelength pulse sources based on spectral slicing is presented,5. A tapered-photonic crystal fiber is designed by combining the advantageous properties of photonic crystal fiber and tapering for generating flat broadband supercontinuum. The fiber is characterized by flattened chromatic dispersion which also decreases from a positive value to a negative one with fiber length. Supercontinuum generation in this photonic crystal fiber was theoretical study. It is shown through theoretical results that the proposed fiber offers the possibility of efficient and flat supercontinuum generation in the telecommunication window using a few picosecond pulses.6. The generation of a flat supercontinuum spectrum of over 90nm in the 1.55μm region by injecting high repetition rate picosecond pulses into a nonlinear dispersion-flattened PCF is demonstrated originally. This flat broadband supercontinuum can simultaneously supply more than 1100 multi-wavelength channels with 10-GHz spacing. The multi-wavelength pulse trains at 10Gbit/s based on spectral slicing are demonstrated experimentally. This supercontinuum source has important applications in dense wavelength division multiplexing （DWDM） optical transmission systems and optical wavelength conversion. Furthermore, numerical simulation is also used to study the generation of supercontinuum in the PCF. An excellent agreement between the simulations and the results of experiment is obtained.7. All-optical regeneration based on self-phase modulation in PCF is proposed and the feasibility of this scheme is investigated both theoretically and experimentally. By combining the PCF with a bandpass filter, a near step-like power transfer function with no pulse distortion is achieved. The device is shown to operate with pecosecond pulses, thus demonstrating the feasibility of this device operating with high bit-rate data signals. The research results confirm the suitability of nonlinear PCF with normal dispersion for all-optical 2R regeneration.8. A highly nonlinear PCF with large anomalous dispersion is proposed to construct nonlinear optical loop mirrors （NOLMs） for pulse compression and shaping. It is shown from numerical results that the proposed NOLMs compress the pulses efficiently and significantly suppresses the pedestals of the pulses.9. Dispersion and dispersion slope compensation of 10 Gbit/s pulses using PCF is demonstrated experimentally. A 26 m PCF was used to compensate the dispersion of 2 km standard singe mode fiber in a 20-nm range in C band. The further research results show that the PCF can compensate the anomalous dispersion of a single mode fiber within±0.3 ps.nm^-1.km^-1 over a 50-nm range from a wavelength of 1520nm to 1570nm.10. All-optical wavelength conversion using four-wave mixing （FWM） in PCF is investigated. The conversion of 10 Gbit/s signal based on FWM in a 30m dispersion-flattened PCF is experimentally demonstrated. The conversion efficiency is around -19.5dB with the fluctuation of less than±1.4dB, which covers a conversion bandwidth of 20nm.更多还原