| 题名 | 室温下多波长掺铒光纤激光器的研究 |
| 作者 | 孙国勇 |
| 学位类别 | 博士 |
| 答辩日期 | 2005 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 王向朝 |
| 关键词 | 多波长 掺饵光纤 光纤激光器 相位调制器 移频器 |
| 其他题名 | Studies on Multi-wavelength Erbium-doped Fiber Laser at Room Temperature |
| 中文摘要 | 光纤通信作为一种通信手段，已经得到了广泛的应用。密集波分复用已成为扩展光纤通信容量的关键技术，作为光源解决方案之一的多波长掺饵光纤激光器吸引了国内外的研究兴趣。随着光接入网技术的发展，在无源光网络中也有很好的应用前景。本文使用速率方程对谐振腔中插入移频器以获得多波长激射的方案进行理论模拟，讨论了各种参数，如有源光纤长度、腔损耗、泵浦功率等对输出功率分布的影响。通过使用相位调制器，在室温下获得了稳定的、无隔离器单向运转的、平坦度高的连续多波长输出。本文的主要内容包括以下几个方面：根据二能级掺饵光纤激光器的速率方程，对单波长光纤环形激光器的工作特性进行了理论分析，得到了光纤激光器在稳态条件下的闭值、输出功率、斜率效率等基本特性的解析表达式。对掺饵光纤激光器的闭值、粒子数分布、斜率效率等参数进行了计算与分析讨论，获得了一些有意义的结果，为单波长掺饵光纤环形激光器的优化设计提供了理论依据。将激光器的速率方程在频域离散化，对谐振腔中插入移频器的多波长掺饵光纤激光器进行了数值模拟。分析表明：激光器的一些参数如掺饵光纤长度、泵浦功率、腔的损耗、移频器的频移量等都会影响激光器输出光谱的平坦度。除此之外，掺饵光纤固有的吸收截面与发射截面的形状也会影响输出功率分布。这些结果对使用移频原理实现掺饵光纤激光器多波长输出的实验工作具有很好的指导意义。对室温单向运转掺饵光纤激光器进行了研究。光纤激光器的谐振腔结构有线形和环形两种。通过对几种不同的环形谐振腔结构的设计，分析计算结果表明可以在不需要隔离器的情况下实现激光的单向运行。选取其中一种谐振腔结构开展了单波长光纤激光器的实验，验证了它的单向性，相反方向的输出功率差大于17dB。周期性滤波器是多波长光纤激光器中的重要器件之一。本文在理论分析的基础上制作了两种周期性滤波器：取样光纤光栅与马赫一曾德滤波器。前者是用振幅板与相位板结合的方法，获得了峰值反射波长间隔为o．snm的取样光纤光栅。后者是用两个3dB定向藕合器级联的干涉仪，透射谱的自由光谱范围为o．gnm。如果将同一侧的两个端口相连，则可以成为反射型滤波器，方便用于线形谐振腔中。反射谱的自由光谱范围为前者的一半，即0.45nm。利用相位调制器插入损耗小，对信号驱动源的要求低等优点，结合优化设计的周I期性滤波器，在室温下实现了稳定的多波长输出。对相位调制器的基本原理进行了理论分析，发现它与移频器的频移机制相同，可见使用移频器的方法实现多波长输出的数值模拟分析对相位调制器同样具有指导意义。根据这些分析，在实验中通过对周期性滤波器的选取，以及激光器参数，如相位调制器的调制幅度与频率等的优化，谐振腔结构的改进，最终在室温下实现了平坦度很高的多波长输出，2dB的输出功率差别内包含了30个激射波长，每个峰值功率的抖动小于士O．5dB。在没有隔离器的情况下实现了激光器的单向运转，实验测得激光器的两个方向输出功率差大于2OdB，而且在实验中发现这一差值与波长和泵浦功率无关。 |
| 英文摘要 | As an important means of communication, optical fiber communication system has been widely implemented. Dense Wavelength Division Multiplexing (DWDM) has become the key technique for capacity expansion. As one of the solutions of optical light source in DWDM system, multi-wavelength erbium-doped fiber laser has attracted the research interest all over the world. With development of optical access network, multi-wavelength optical sources also have the great potential to be used in passive optical networks. In this dissertation, the multi-wavelength lasing by inserting frequency shifter into resonant cavity is theoretically analyzed based on the rate equations. The impact of active fiber length, cavity loss and pump power on output power distribution is discussed. By utilizing phase modulator, a stable fiber laser with unidirectional operation without isolators and highly uniform continuous multi-wavelength output at room temperature is accomplished. The main contents in this thesis are as follows: Based on the rate equations of two-level erbium-doped fiber laser, operation characteristics of the single-wavelength ring laser are theoretically analyzed. The analytical expressions of some basic characteristics have been derived under stationary condition; such as threshold pump power, output power, slope efficiency and etc. Some useful results have been obtained from the calculation and analysis of the threshold, carrier distribution, and slope efficiency of erbium-doped fiber laser. And these results supply the theoretical foundation for characteristics optimization of single-wavelength erbium-doped fiber ring laser. Discretizing the rate equations in frequency domain, numerical simulation on multi-wavelength erbium-doped fiber laser by inserting frequency shifter into resonator is carried out. According to analysis, some parameters, for example, erbium-doped fiber length, pump power, cavity loss and shifted frequency amount of the frequency shifter will influence the flatness of the output spectrum. What's more, the inherent line shape of absorption and emission cross-section will also change the output power distribution. These results provide good instruction for realizing multi-wavelength output from erbium-doped fiber lasers based on frequency shifting principle. The unidirectional erbium-doped fiber laser at room temperature has been studied. Cavity of fiber lasers could be two types: linear or ring cavity. By designing several different configurations of ring cavity, unidirectional operation can be obtained even without isolators. Experiment of single-wavelength fiber laser with a certain cavity configuration was employed to verify the analysis. Output difference from the opposite directions is larger than 17dB, which proves its unidirectional operation. Periodic filter is one of the important components in multi-wavelength fiber lasers. Two periodic filters are made based on theoretical analysis in this thesis: sampled fiber grating and Mach-Zehnder filter. Sampled fiber grating was made by combining amplitude mask and phase mask. Wavelength interval of the series peaks is 0.8 run in reflective spectrum. The latter is an interferometer by cascading two 3dB fiber couplers, and its free spectral range is 0.9nm in its transmission spectrum. When the two ports at the same side are connected, it becomes a reflective comb filter with free spectral range of 0.45nm. Therefore, it is convenient to be used in linear cavities. Because of some good characteristics of the phase modulator such as low insertion loss and demand on driving signals, stable multi-wavelength output at room temperature has been implemented, combing with optimized periodic filters and phase modulator. The basic principle of phase modulator was analyzed and it can be seen that phase modulator has the same operation mechanism as the frequency shifter. Hence, the analyzed results based on frequency shifter are still valid for realizing multi-wavelength lasing in erbium-doped fiber laser with phase modulator. According to these analyses, highly uniform multi-wavelength output was finally obtained by choosing the comb filter, optimizing the laser parameters such as modulation amplitude and frequency of the phase modulation, and amending the cavity structures. Power uniformity is lower than 2dB among 30 lasing wavelengths, and peak-power fluctuation of each wavelength is less than ±0.5dB . The unidirectional operation was achieved without isolators experimentally. The output power difference is higher than 20dB from the opposite directions. Moreover, it does not depend on the lasing wavelength and pump power. |
| 语种 | 中文 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15517]  |
| 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 | 孙国勇. 室温下多波长掺铒光纤激光器的研究[D]. 中国科学院上海光学精密机械研究所. 2005. |
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