少模光纤布拉格光栅失量模耦合特性的研究

发布时间：2018-03-05 21:39

本文选题：耦合模理论　切入点：布拉格光栅　出处：《北京交通大学》2017年硕士论文　论文类型：学位论文

【摘要】：模分复用是继时分复用和波分复用等复用技术后的一种新型复用技术,利用不同的模式传输信息,能够极大地提高通信系统的容量。目前的研究现状表明,实现模分复用的方式可能有多种,而有效生成高阶矢量模成为了一些模式复用方法的关键因素。基于以上研究背景,本文提出了一种基于FBG(Fiber Bragg Grating)实现基模耦合到高阶矢量模的新方法。应用闪耀光纤光栅全矢量复模理论,研究了基于阶跃型少模光纤和环形少模光纤的单侧紫外光曝光写入的FBG,实现了基模到高阶矢量模(TE01、TM01和HE21)的耦合。分析了紫外光指数分布的衰减因子α、光栅幅度函数χ以及光栅长度等因素对耦合特性的影响。对于基于阶跃型少模光纤的FBG,研究表明,通过合理调节光栅的各个参数,可以实现高效的矢量模式耦合;但是阶跃型少模光纤无法将LP111模式群的简并矢量模进行有效分离。对于基于环形少模光纤的FBG,研究表明,由于此环形光纤结构能够打破LP111模式群中矢量模式的简并性,高阶矢量模间的模式有效折射率差达到1.8×10-4,可以在不同反射波长处实现高效耦合。耦合系数和反射率随紫外光指数分布的衰减因子α的变化存在优化极值点。随着光栅幅度函数,值的增大,反射率会增大,反射峰位置向长波长方向移动,同时反射谱会变宽。在χ值增大的过程中,TE01模和HE21 s模会发生相互作用,使反射率下降,且两者的反射峰相对位置会发生互换。本论文提出的实现基模耦合到高阶矢量模的FBG,为光纤中高阶矢量模式的生成提供了新的技术手段,在模分复用技术研究领域具有重要应用价值。
[Abstract]:Module division multiplexing is a new type of multiplexing technology after time division multiplexing (TDM) and wavelength division multiplexing (WDM). Using different modes to transmit information can greatly improve the capacity of communication system. There may be many ways to realize module division multiplexing, and the efficient generation of high-order vector modules has become the key factor of some pattern multiplexing methods. In this paper, a new method based on FBG(Fiber Bragg Gratingis proposed to realize the coupling of fundamental mode to high order vector mode, and the blazed fiber grating full vector complex mode theory is applied. The FBGs written by single-side ultraviolet light exposure based on step less mode fiber and ring less mode fiber are studied. The coupling of base mode to higher order vector mode TE01 and HE21) is realized. The attenuation factor 伪 and the grating amplitude function of the exponential distribution of ultraviolet light are analyzed. The effect of the number 蠂 and the grating length on the coupling characteristics. For the FBG based on the step less mode fiber, it is shown that, The efficient vector mode coupling can be realized by adjusting the parameters of the grating reasonably, but the degenerate vector mode of the LP111 mode group can not be effectively separated by the step less mode fiber. Because this ring fiber structure can break the degeneracy of vector mode in LP111 mode group, The difference of effective refractive index between higher order vector modes reaches 1.8 脳 10 ~ (-4), which can achieve high efficiency coupling at different reflectance wavelengths. The variation of coupling coefficient and reflectivity with the attenuation factor 伪 of ultraviolet light exponent distribution is optimized. With the increase of 蠂 value, the reflectivity will increase, the position of the reflection peak will move to the direction of long wavelength, and the reflection spectrum will become wider. In the process of increasing 蠂 value, there will be interaction between the HE21 s mode and the TE01 mode, which will decrease the reflectivity. The relative position of the two peaks will be interchangeable. In this paper, the FBGs which realize the coupling of the base mode to the higher-order vector mode provide a new technique for the generation of high-order vector mode in optical fiber. It has important application value in the research field of module division multiplexing technology.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN253

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