若干熔锥型光纤器件的理论和实验研究
文献类型：学位论文
| 作者 | 罗爱平 |
| 学位类别 | 博士 |
| 答辩日期 | 2004 |
| 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 | 熔锥型光纤耦合器 光纤光栅 滤波器 非线性开关 倏逝波耦合 |
| 其他题名 | The theoretical and experimental investigations of fusion-tapered fiber devices |
| 中文摘要 | 熔锥型光纤器件作为光纤器件中最具代表性的基础器件，以其极低的附加损耗、良好的稳定性、低廉的制作成本等优点在光纤通信系统中得到广泛的应用。在光纤传感领域也有着重要的应用。本文对基于熔锥型光纤器件的一些特性进行了理论和实验研究，目的是在现有成熟的熔锥型光纤器件之外，进一步研究熔锥型光纤的特性和机理，为探索和开发新型的熔锥型光纤器件及其应用提供理论和实验依据。论文首先采用超模理论和局部模式理论对熔锥型光纤祸合器的特性进行了理论分析和计算。论文从熔锥型光纤祸合器的模型出发，采用有限差分法数值，求解了祸合器横截面的模场分布以及模式的有效折射率的变化特性；分析了祸合器结构的绝热近似条件，从光在祸合器中的传输特性角度对祸合器的超模与光纤的基模进行了等效分析。这为研究熔锥型光纤器件的特性提供了理论依据。论文在超模理论的基础上，对在普通光纤藕合器上写入光栅制作滤波器的特性进行了理论和实验研究。首先，采用互易定理推导了描述祸合区光栅特性的藕合的超模方程组；然后，分析了在实际测量的3dB藕合器、100％祸合器和零祸合器的藕合区写入布拉格光栅后的特性。数值结果表明，在这些普通的藕合器上写入光栅同样可以制作滤波器，且写入的光栅存在最佳位置和最佳长度。同时我们提出了在藕合区写入非线性啁啾光栅以获得边带抑制的、窄线宽的滤波器。在实验研究中，利用244nm的氢离子倍频激光器实验研究了在3dB祸合器的熔锥区写入布拉格光栅制作滤波器的特性。实验结果进一步表明用普通藕合器可以实现多端口波长选择滤波器。基于光纤藕合器的非线性全光开关，在超快现象的处理方面具有重要的应用。论文对祸合器的非线性开关特性进行了理论和实验研究。首先运用超模理论推导出描述熔锥型祸合器的非线性效应的藕合模方程组；然后采用龙格一库塔法数值研究了零藕合器和100％藕合器在输入连续光波时的非线性开关特性。在数值计算过程中，为更准确的模拟非线性特性，考虑了纤芯有效面积随祸合器的结构变化的特性。在实验研究中，利用飞秒激光测量研究了SNIF-28光纤和多模光纤的非线性损耗特性，测量研究了100％耦合器和零耦合器祸合比的非线性效应。近几年来，锥形光纤在光信息领域受到普遍的关注。论文采用CO2激光器和扫描光束法制备了双锥形光纤。论文改进了扫描镜驱动电压的波形，获得了中间功率分布较高且均匀、两端功率较低的加热区，由此拉制了具有均匀腰区的双锥形光纤。论文研究了不同拉锥速率时，在拉锥过程中光传输的损耗。对双锥形光纤的不同锥形过渡区的形状以及均匀腰区的长度和大小进行了测量研究，获得了与理论分析一致的结果。论文提出了一种建立在长周期光纤光栅和双锥形光纤基础上的倏逝波祸合作用，并从理论和实验两方面进行了研究。合理设计长周期光栅和双锥形光纤的参数，当它们的包层密切贴合时，由于长周期光栅的作用而损失到包层模的能量，可以从双锥形光纤中祸合出来，藕合特性同锥形光纤的几何形状、长周期光纤光栅谐振损耗峰的阶次、两光纤的位置等因素有关。实验研究获得了1550nm波段长周期光纤光栅与双锥形光纤藕合的输出，输出光谱与长周期光纤光栅损耗谱符合良好；测量了不同藕合位置下藕合效率的变化，与理论分析一致。这一工作为监测实际应用系统中长周期光纤光栅的特性提供了一种新方法；为利用锥形光纤和长周期光纤光栅开发新型光纤器件，提供了一种富有应用前景的方案。 |
| 英文摘要 | The fusion-tapered fiber device, as the most typical fundamental fiber device, has extensive applications in fiber communication systems due to its low excess loss, good stability, cheap cost and so on. It has also important applications in the field of fiber sensing. In this thesis, some characteristics of this kind of devices were investigated theoretically and experimentally. The purpose of the dissertation is to further study the characteristics and mechanism of the fusion-tapered fiber, and to provide the experimental and theoretical basis for exploiting novel devices based on fused fibers. Beginning with the model of the fusion-tapered fiber coupler, the characteristics of the couplers were analyzed with super-mode theory and local mode theory. The distribution of the mode field and the corresponding indices were calculated with finite difference method. The adiabatic criteria of the coupler and the equivalent analysis between the super-mode and the fundamental mode of the fiber were also given. The studies provide theoretical basis for analyzing fusion-tapered fiber devices. Based on the super-mode theory, the characteristics of conventional fused coupler incorporated with Bragg grating were investigated and analyzed numerically and experimentally. Firstly, the coupled super-mode equations were deduced with reciprocity theorem. Then, as examples, three kinds of typical couplers, 3dB coupler, 100% coupler and null coupler, made of Corning SMF 28TM step index fibers were analyzed with their experimental fitted shapes. The numerical results show that the high drop efficiency filter can be obtained with these conventional hydrogenated couplers. And there exists optimized position and grating length. At the same time, a nonlinear chirped grating is proposed to be written into the coupler in order to obtain narrow bandwidth and side-lobe suppressed spectrum of this component. In experiments, the filters based on 3dB couplers with Bragg gratings written by a 244nm Ar+ frequency-doubled laser in the coupling regions were fabricated. The experimental results also show that the multi-port wavelength-selective filter can be realized with conventional couplers. On the other hand, the nonlinear all-optic switching device based on fiber coupler has important applications in ultrafast processing. The nonlinear switching characteristics of the fused fiber coupler were studied theoretically and experimentally. The nonlinear coupled super-mode equations were deduced firstly. Then the null coupler and 100% coupler were numerically investigated with Runge-Kutta method at the case of injecting continuous wave. In calculation the variation of the effective core area versus the length of the coupler was taken into account. In experimental study, the nonlinear optical losses in single mode and multimode fibers were measured by using a femto-second laser. The nonlinear output of 100% coupler and null coupler were also experimentally investigated. In recent years, the tapered fiber has attracted wide attention in the field of optic information. In the dissertation, the tapered fiber was fabricated with CO2 laser and beam scanning method. The wave shape of driven voltage was improved and the heated region with higher, uniform power at the center and lower power at the two ends were obtained. Then the bi-conically tapered fiber with uniform waist was fabricated correspondingly. The signal transmission losses versus different tapered speeds were also investigated. The shape of the taper transition, the length and diameter of the waist obtained with improved method were measured, and were found to be in accordance with the theoretical results. A novel evanescent-field coupling based on bi-conically tapered fiber and LPG was proposed and theoretically and experimentally investigated. The light coupled to the cladding modes by LPG can be transferred to a bi-conically tapered fiber by appropriately designing the parameters of the tapered fiber and LPG. The characteristics of this kind of coupling depend on the shape of the tapered fiber, the order of the resonant loss peak of LPG and the position of the two fibers. The coupled output at around 1550nm was obtained experimentally, and the output spectrum is in good agreement with the loss spectrum of the LPG. The experimental variation of the coupling efficiency with different coupling position was measured to be consistent with the theoretical analysis. This kind of evanescent-field coupling can be used to monitor the characteristics of LPG, and provide a potential useful method in developing new devices based on tapered fiber and LPG. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15339]  |
| 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 | 罗爱平. 若干熔锥型光纤器件的理论和实验研究[D]. 中国科学院上海光学精密机械研究所. 2004. |
入库方式： OAI收割
来源：上海光学精密机械研究所
浏览0
下载0
收藏0
其他版本
除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。