【作者】 张华；

【导师】 文双春；

【作者基本信息】 湖南大学 ， 计算机应用技术， 2005， 硕士

【摘要】 光子晶体光纤是近年来提出来的一种全新的光纤,它具有传统光纤所无法比拟的特殊的光学特性,如无截止单模、可控色散以及丰富的光学非线性等特性,在全光通信领域具有广阔的应用前景,已成为光纤通信领域的一个研究热点。光子晶体光纤的奇异特性决定了光脉冲在其中的传输特性与传统光纤中有很大区别,本文利用解析和数值模拟的方法研究了光子晶体光纤中的调制不稳定性,用数值模拟方法证明了利用调制不稳定性可以产生超短脉冲序列。此外,用数值模拟方法分析了超短脉冲在光子晶体光纤中的传输特性及超连续谱产生。取得的主要成果如下: 第一,光子晶体光纤中光脉冲的传输受多种物理因素的制约,理论分析十分复杂,数值模拟成为重要的分析手段。我们基于光子晶体光纤中光脉冲传输的物理模型自主开发了能模拟光脉冲线性和非线性传输过程的计算机程序,与文献报道的理论和实验结果进行了比对,考核了程序计算结果的正确性。 第二,利用线性稳定性分析方法研究了光子晶体光纤中超短脉冲的调制不稳定性,获得了调制不稳定性增益谱的一般表达式,它涵盖了高阶色散、自陡峭、受激喇曼散射等各种高阶效应对调制不稳定性的影响。理论结果表明,只有偶数阶色散对增益谱有影响,且会产生多个新的不稳定区域,而奇数阶色散则不起任何作用;受激喇曼散射效应可以产生新的不稳定区域,且随着功率的增长,新区域会与原有的正常不稳定性区域融合在一起;自陡峭效应对调制不稳定性的增益谱影响很小。利用数值模拟方法验证了理论结果的正确性,并证明利用光纤反常色散区的调制不稳定性可以有效的产生超短脉冲序列。 第三,分析了三种具有典型色散曲线分布的光子晶体光纤中超短脉冲的传输特性。数值模拟结果发现,在三类光纤的传输初期都只有群速度色散和自相位调制效应起主要作用;随着传输距离的增加,在远离零色散点的具有反常色散曲线的光纤中,受激喇曼散射起主要作用,脉冲的中心波长向长波长方向偏移,出现孤子自频移现象;在近零色散具有反常色散曲线的光纤中,高阶色散起主要作用,出现高阶孤子分裂,脉冲频谱被极大展宽;在远离零色散具有正常色散曲线的光纤中,高阶效应基本不起作用,脉冲波形对称展宽近似成矩形,频谱也对称展宽,但展宽范围小于前面两种情况。更多还原

【Abstract】 Photonic crystal fibers(PCFs), demonstrated in recent years, have some unique characteristics such as endlessly single mode, controllable dispersion and rich optical nonlinearity compared with the conventional fibers. PCFs have exhibited wider application potentials in all-optical communication, and have become a hot research topic in optical communication. The unique properties of PCFs make them quite different from conventional fibers in many aspects. In this thesis, we study modulation instability (MI) in PCFs analytically and numerically, and prove a new way to generate an ultra-short pulse sequence based on MI. Furthermore, the propagation properties of ultra-short pulses and supercontinuum generation in PCFs are analyzed. The main research results are listed below:Firstly, the propagation of ultra-short optical pulses in PCFs is limited by many physical factors, and the theoretical analysis is very complicated, so numerical simulation becomes crucial research methods. Based on the physical model of optical pulses propagation in PCFs, we have independently developed the computer program which can simulate the process of linear and nonlinear propagation of optical pulses. Compared with the experimental and theoretical results reported in literatures, the validity of the computation results of our program is confirmed.Secondly, we use the standard linear stability analysis to study MI in PCFs. An generic expression for MI gain spectrum which includes the influence of higher-order effects such as higher-order dispersion (HOD), self-steepening (SS), stimulated Raman scattering (SRS) etc. on MI has been obtained. The theoretical results show that only even-order dispersions influence gain spectrum and they lead to the appearance of new MI regions, whereas odd-order dispersions contribute nothing to MI. SRS can generate an additional MI region and the new region is gradually screened from the conventional MI region as the initial power increases. SS exerts little influence on MI gain spectrum. Numerical simulation confirms the theoretical results and proves that an ultra-short pulse sequence can be generated by MI in the anomalous dispersion region in optical fibers.Thirdly, the characteristics of ultra-short pulses propagation in three kinds of PCFs which have typical dispersion profiles are analyzed. Numerical simulations show that group velocity dispersion and self-phase modulation take main effects in the更多还原