用于光纤色散补偿的若干光子器件的研究
文献类型：学位论文
| 作者 | 李琳 |
| 学位类别 | 博士 |
| 答辩日期 | 2003 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 方祖捷 |
| 关键词 | 光纤色散补偿 啁啾光纤光栅 色散测量 |
| 其他题名 | Study on fiber dispersion compensation devices |
| 中文摘要 | 当代光通信系统在网络数据业务“爆炸式”增长的催化中也迅速增长，光信道的单通道速率从IOGbit／s正在向40Gbit/s迈进；同时在基于密集波分复用技术的光通信系统中，单纤复用波长也从4个向160个波长甚至更多发展，可以预见大容量、高速率的光通信系统将在通信系统中广泛应用。而光纤色散问题在大容量高速系统中显得越来越重要，因为光纤色散是制约高速光通信系统发展的重要因素，在10Gbit/s或者传输速率更高的系统中，光纤色散会造成光信号脉冲的展宽，引起信号之间的码间干扰，劣化系统信噪比，增加误码率等等。本文从理论和实验上研究了若干基于啁啾光纤光栅的色散补偿光子器件，针对不同应用制备不同特性的啁啾光纤光栅的色散补偿器件，本论文的研究内容主要概括为以下几个方面：从非线性薛定谔方程出发，研究光脉冲在光纤色散介质中的脉冲演化过程。对于高速光通信系统，由于高速率和大容量，导致光纤一阶色散对于光脉冲的展宽作用不可忽视。光纤脉冲的展宽与其传输距离和传输速率有关。在高速系统中，如果保持光脉冲的脉宽不改变，那么传输速率增加一倍，传输距离就要减小到四分之一。啁啾光纤光栅是良好的无源色散补偿器件，采用藕合模理论分析和优化用于色散补偿的啁啾光纤光栅的特性。对于线性啁啾光栅，其周期啁啾率和色散补偿量成反比例，所以用于色散补偿的啁啾光栅只具有较小的惆啾率。另外，采用有效介质理论，分析了啁啾光栅群时一延曲线的抖动问题，为优化光栅的色散特性和滤波特性提供理论基础。此外，采用层析散射法来设计所需滤波特性的啁啾光栅，能在一定程度上指导实际光栅的制备。利用啁啾相位版制备了线性啁啾光纤光栅，其技术指标为：工作波长为ITU-T规范的波长，色散量在800-1000ps／nm，带内插入损耗在ldB左右，偏振模色散小于l0Ps，群色散抖动在 15Ps左右。这种无调谐装置的惆啾光栅，已经可以用于80km的高速光网络的色散补偿。为了符合下一代光网络的灵活动态配置的要求，本论文着重研究了动态色散补偿技术。在温度调谐式色散补偿器件的研究方面，攻克了光纤金属化的工艺难关，实现在光纤外层电镀上金属薄膜，作为低功率微型加热器。通过电流调谐，可以获得调谐范围在2.3nm的可调谐滤波器件，并对温度调谐器件的时间响应进行研究。采用简单热能传输方程，分析了金属化光纤内部的热能分布，从而获得光栅在电流调制作用下的时间相应特性，实验测得金属化光栅的时间响应常数为0.6s。这也表明目前温度调谐的响应速度较慢。在应力调谐方面，采用简单的悬臂梁结构，当啁啾光栅斜贴于悬臂梁侧面时，可以在实现色散量动态调节的同时，保持光栅的中心工作波长不发生漂移。应力调谐方式更具有实用性和稳定性。在10GbPs的高速系统实验中，啁啾光纤光栅可以用于80km光纤的色散补偿，在补偿120km光纤系统时仅给系统增加1.5dB的色散功率代价。从理论上研究基于G-T干涉仪的色散补偿技术，由于G-T干涉仪本身就具有良好的周期性色散特性，适合于多信道色散补偿。在本论文中，给出一种复合腔G-T干涉仪的结构，可以实现色散量的动态调节。提出了一种采用主动锁模激光器原理来测量器件色散参数的色散测量方法。啁啾光纤光栅作为外腔激光器的外腔反射面，通过微波射频注入技术，将外腔激光器的激射频率锁定在特殊频率上，从而得出这一频率上的群时延数值。与其他测试方法相比，这种方法的输出功率较高，易于探测，具有较高的精度和可靠性。 |
| 英文摘要 | Boosted by the explosion of networks data services, the capacity of the present optical systems grows up quickly, per-channel rate increasing from 2.5 Gbps to 40Gbps, while per-fiber channel numbers is increased from 4 to 160. So it seems that large-capacity and high-speed optical networking will be widely used in the future, As a result, fiber dispersion will play an important role in high-capacity optical systems, since fiber dispersion is one of factors limiting the system transmission distance. In lOGbps or more high-rate optical system, fiber dispersion leads to the broadening of optical pulse that induces the inter-symbol interference, deteriorates the signal-to-noise ratio performance and increases the bit error rate. In this thesis, chirped fiber Bragg grating based dispersion compensators are studied on according to their applications, the research contents include: According to Schrodinger equation, the evolution of optical pulse in the fiber is carefully studied. For large-capacity and high-speed system, the pulse broadening induced by fiber first-order dispersion will no longer be negated. There is a certain relationship between pulse broadening and transmission distance. If the speed fasts by one time, the transmission distance will be four times decreased to keep the pulse broadening the same. Chirped fiber Bragg grating is good at dispersion compensation for its fine filter characteristics and is analyzed by coupled-mode theory. For linear chirped fiber Bragg grating, the period chirp rate is inversely proportional to the dispersion amount. Therefore the smaller the chirp rate is, the large the dispersion amount is. Also, studies on group delay ripples using effective medium theory makes an instruction for manufacture process. The typical specifications of chirped fiber Bragg grating by chirped phase mask technique are the center wavelengths agreed to ITU-T grid, 800-1000ps/nm dispersion amount, about ldB in-band insertion loss, below lOps polarization mode dispersion and about ±15ps group delay ripple. As a result of systems experiments, chirped fiber grating can do dispersion compensation in 80km long distance optical system, and also compensate for 120km system with below 1.5dB power penalty. Due to the requirements of flexibility, tunability and reconfiguration in the next generation networks, several tunable dispersion compensation techniques are analyzed in details in the thesis. For temperature controlling dispersion compensator, fiber Bragg grating is dealt with by the metal-coated processing. The thin film coating outside the fiber cladding is regarded as micro-heater to change the local temperature distribution of the fiber through applying current. In the experiment, the center wavelength of fiber Bragg grating could be 2.3nm with 200mA current. Meanwhile, the real time response of tunable filter is also analyzed through heat energy transfer equation. Under the condition of energy conversation, the distribution of heat energy inside the fiber is deduced and therefore the real time response of metal-coated fiber Bragg grating is obtained as a function of electronic current. Derived from experimental data, the time constant of metal-coated FBG is 0.6s, which indicates that the temporal response of temperature controlling seems slow. For strain controlling dispersion compensator, simple cantilever beam is used to apply strain distribution to chirped fiber Bragg grating. When chirped fiber Bragg grating is stuck onto the cantilever beam with a small angle, its center wavelength becomes stable while the dispersion amount is precise adjusted. The method based on strain controlling is more useful and reliable. In lOGbps high-speed system, the favorable dispersion compensation distance of chirped fiber Bragg grating is 80km, and additional power penalty is about 1.5dB for 120km long haul. Theoretical analysis of the characteristics of G-T interferometer is due to its periodical property and potentially suitable for multi-channel dispersion compensation. In the thesis, a compound structure G-T dispersion compensator is proposed for tunable dispersion compensation with large dispersion dynamic range. At last, a dispersion measuring method based on passive mode-locked laser principle is proposed as a way to test the group delay of chirped fiber Bragg grating. In this method, chirped fiber Bragg grating is used as outside reflection mirror of external cavity laser. Radio frequency sending into the external cavity laser locks the actuated frequency and stabilizes the output of laser at a certain wavelength. Thus, the group delay can be deduced as a function of laser wavelength. This method is high-power output, easy to detach, high resolution and reliability. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15333]  |
| 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 | 李琳. 用于光纤色散补偿的若干光子器件的研究[D]. 中国科学院上海光学精密机械研究所. 2003. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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