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1、STUDY ON TWO FEATURES OF THEOPTICAL FIBER LASERName: Shule LiResearch field: OpticsSupervisor: Qishun ShenDepartment of PhysicsShanghai Jiaotong University2007.6光纤激光器两个特性的理论与实验研究摘要对光纤激光器的研究在当今光通信技术发展中具有十分重要的意义。双稳态激光器是光开关，光逻辑运算等应用领域的重要部件。而多波长激光器，则是 WDM等应用领域的重要部件。本文即针对光纤激光器中的双稳态和多波长做深入的探讨。我们在实验中发现，即使在
2、简单构造的以掺铒光纤为增益介质的光纤激光器中也能得到双稳态激光。使用传统的掺铒光纤三能级模型，并引入“无用泵浦损耗”这一新的概念，我们能够通过理论计算验证光纤激光器中双稳态的存在，并得到与实验符合得很好的结果。通过理论计算，进一步明确了双稳态的存在与否及其区间大小与掺铒光纤的长度等诸多因素有关。这些发现为我们进一步控制光纤激光器双稳态提供了理论基础。可调多波长光纤激光器，在光通信领域有良好的应用前景。Lyot-Sagnac滤波器由多段保偏光纤的光纤环构成。它能够实现对所需的波长间隔进行滤波。进一步在滤波器中加入偏振控制器（PC）等器件，就可以通过调节滤波器的几何构型实现波长间隔的调节。半导体光
3、放大器(SOA)的非均匀加宽特性对产生多波长激光非常有利。本文对两段式Lyot-Sagnac滤波器进行了详细的理论分析，实现了一种基于 SOA的新型多波长光纤激光器。它利用 Lyot-Sagnac滤波器的波长选择性，在室温下得到了约 18个具有 30dB信噪比的多波长激光输出。波长范围在1556nm到 1577nm之间。通过调节 Lyot-Sagnac环内的偏振控制器，多波长激光的波长间隔可在两种 ITU 标准波长间隔（0.4nm和 0.8nm）间选择。这种构型的光纤激光器具有稳定性好，波长间隔可控，信噪比高等优点。它在大规模 WDM光网络中具有良好的应用前景。关键词: 激光技术，光纤激光器，
4、光学双稳态，多波长激光器，Lyot-Sagnac滤波器，半导体光放大器STUDY ON TWO FEATURES OF FIBER LASERABSTRACTThe research on fiber laser plays an important role in the development ofoptical communication technology nowadays. Bi-stable laser is the keydevice in optical switching and optical logic. Multiwavelength laser plays akey
5、 role in the technology of WDM. In this thesis, we will study thebistability and multiwavelength phenomenon in fiber lasers.In our experiment, we observed that optical bistability can exist even ina simple fiber laser employing erbium-doped fiber (EDF) as a gain medium.Based on the traditional three
6、-level model and by introducing useless pumploss into it, we can build a model to prove that this bistabilitys existance.The calculation result fits our experiment well. Moreover, by building thetheory of optical bistability in fiber laser, we can also find out the dependenceof the bistability on va
7、rious parameters, such as the length of the EDF. Theseresults provides a theoretical basis for us to control the bistability in a fiberlaser.Lyot-Sagnac filter is composed by several segments of polarizationmaintaining fiber (PMF). It can be used as a filter for any grid spacingwanted. If polarizati
8、on controllers (PC) are added into this filter, the gridspacing obtained can be switched from one to another by adjusting these PCs.The semiconductor optical amplifier has the feature of inhomogeneousbroadening, which makes it an ideal gain medium for constructingmultiwavelength fiber lasers. A nove
9、l multiwavelength fiber laser employinga semiconductor optical amplifier within a fiber ring cavity is proposed onthe basis of the theoretical analysis of the Lyot-Saganc filter with twosegments of PMF. This fiber laser can generate 18 multiwavelength laserswith signal-to-noise ratio (SNR) 30dB, ran
10、ging from 1556nm to 1577nm.The grid spacing of the output laser can be selected between ITU gridspacings: 0.4nm and 0.8 nm, at room temperature. This kind of fiber lasershas good tunability and stability with a high signal-to-noise ratio. It can beused in the WDM networks employing an interleaved wa
11、veband concept.KEYWORDS:lasertechnique,fiberlaser,opticalbistability,multiwavelength laser, Lyot-Sagnac filter, semiconductor optical amplifier目录摘要ABSTRACT第一章绪论 11.1光纤激光器简介 21.2光纤激光器中的双稳态现象 31.3光纤多波长激光 41.4多波长光纤激光器的研究进展 7本章小节第二章光纤激光器原理 92.1光纤激光器的基本结构 92.2 DWDM技术简介 112.3 ITU-T标准 13本章小节第三章光纤激光器中的双稳态现象
12、 153.1光纤激光器中的双稳态实验研究与实验解释 153.2掺铒光纤的三能级近似 193.3解释双稳态现象的理论模型 203.4数值模拟及对结果的分析 22本章小节第四章多波长光纤滤波器 274.1两段式 Lyot-Sagnac滤波器的理论分析 274.2 N段式 Lyot-Sagnac滤波器的理论分析 314.3环境对 Lyot-Sagnac滤波器的影响 34本章小节第五章半导体光放大器的增益特性 375.1 SOA原理简述5.2 SOA的理论模型本章小节 37 40第六章基于半导体光放大器的多波长光纤激光器研究 486.1以 SOA为增益介质的多波长光纤激光器的实验组成 486.2基于 SOA的可调多波长光纤激光器实验结果分析 496.3对信噪比及环境敏感度的分析本章小节 51第七章总结与展望 54参考文献
