Bragg少模光纤的设计与性能分析

发布时间：2018-09-12 08:38

【摘要】：随着光纤通信网络的快速发展,现有单模光纤的通信容量已接近其香农极限,逐渐无法满足当今信息日益增长的需求。模分复用技术可以很好地解决光纤通信容量日益饱和这一问题,而少模光纤则是模分复用系统中的关键器件。纤芯内支持一定数量模式传输的光纤,称为少模光纤。少模光纤与单模光纤相比的一大优点是可以采用模分复用技术来增大少模光纤的传输容量;同时,少模光纤结构参数在合理范围内的改变,可以控制光纤中传导模式的数量,有效地降低模式色散和模间串扰。此外,少模光纤还可应用于光纤光栅和光纤传感等领域。为了获得一种适合于工作在1550nm波长的Bragg少模光纤,本文提出了一种工作波长为1550nm的Bragg少模光纤,通过分析Bragg光纤的损耗来源以及材料特性,选取SiO2和Si作为Bragg光纤包层材料,并确定其包层晶格周期为4μm。利用基于全矢量有限元法(FEM)的仿真软件COMSOL Multiphysics进行仿真计算,从传输容量和模式损耗两方面考虑,对空心Bragg少模光纤的结构参数进行优化,当Bragg光纤结构参数为:纤芯内径为9.3μm,包层直径为117.6μm,包层周期数为13,晶格周期为4μm,SiO2和Si介质层的厚度分别为2.9μm和1.1μm,包层第一周期为4.15μm时,实现了其在1550nm的大容量、低损耗传输,可以同时传输7个线偏振模式,其中6个线偏振模式的损耗低于0.01 dB/m且LP31模损耗低至1.8E-4dB/m,优于已有的少模光纤的性能。考虑到制备工艺的不完善性,本文分析了在Bragg光纤制备过程中可能出现的结构误差,如纤芯大小或形状发生改变、纤芯与包层圆心发生偏离。仿真结果表明,以上结构误差均会使Bragg光纤传输容量减小,损耗增大,且随着结构误差的增大,Bragg光纤原有的性能急剧劣化。因此在光纤制备过程中应尽量避免引入较大的结构误差,影响Bragg光纤原有的大容量、低损耗特性。研究结果对指导Bragg少模光纤制备,避免制备过程中的误差对光纤性能产生影响具有重要意义;同时可以加快Bragg少模光纤以及相关模分复用系统的实用化进程,使光纤通信容量进一步提高。
[Abstract]:With the rapid development of optical fiber communication network, the communication capacity of the existing single-mode optical fiber is close to its Shannon limit and can not meet the increasing demand of information. Mode division multiplexing technology can solve the problem of increasing saturation of optical fiber communication capacity, and less mode fiber is the key device in mode division multiplexing system. The fiber in the core that supports a certain number of modes of transmission is called a small mode fiber. One of the advantages of low-mode fiber compared with single-mode fiber is that mode division multiplexing technique can be used to increase the transmission capacity of low-mode fiber, and the number of conduction modes can be controlled by changing the structural parameters of low-mode fiber within a reasonable range. Mode dispersion and inter-mode crosstalk are effectively reduced. In addition, the low-mode fiber can also be used in fiber grating and fiber sensing and other fields. In order to obtain a kind of Bragg low-mode fiber suitable for working at 1550nm wavelength, a kind of Bragg low-mode fiber with working wavelength of 1550nm is proposed in this paper. By analyzing the source of loss and material characteristics of Bragg fiber, SiO2 and Si are selected as the cladding materials of Bragg fiber. The cladding lattice period is determined to be 4 渭 m. The simulation software COMSOL Multiphysics based on full-vector finite element method (FEM) is used to simulate and calculate the structural parameters of hollow Bragg low-mode fiber from the aspects of transmission capacity and mode loss. When the structure parameters of Bragg fiber are as follows: core diameter 9.3 渭 m, cladding diameter 117.6 渭 m, cladding cycle number 13, lattice cycle 4 渭 m and Si dielectric thickness 2.9 渭 m and 1.1 渭 m, respectively. Seven linear polarization modes can be transmitted at the same time. The loss of six linear polarization modes is less than 0. 01 dB/m and the loss of LP31 mode is as low as 1. 8 E-4 dB / m, which is superior to the performance of the existing low mode fiber. Considering the imperfection of the fabrication process, the possible structural errors in the fabrication of Bragg fiber are analyzed, such as the change of the core size or shape, and the deviation between the core and the core of the cladding. The simulation results show that the structural errors above can reduce the transmission capacity and increase the loss of Bragg fiber, and with the increase of structural error, the original performance of Bragg fiber will deteriorate sharply. Therefore, large structural errors should be avoided in the fabrication process of Bragg fiber, which will affect the original large capacity and low loss characteristics of Bragg fiber. The research results have important significance to guide the preparation of Bragg low-mode fiber and avoid the influence of errors in the fabrication process on the performance of fiber, and can accelerate the practical process of Bragg low-mode fiber and related mode-division multiplexing system. The capacity of optical fiber communication is further improved.
【学位授予单位】：南京邮电大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN253

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