模分复用系统中少模光子晶体光纤及模式转换器的设计及研究

发布时间：2018-05-31 01:01

本文选题：模分复用 + 少模光子晶体光纤　；参考：《南京邮电大学》2017年硕士论文

【摘要】：近年来,波分复用系统因单模光纤的非线性容忍度小,传输容量越来越接近香农极限。为了进一步扩充光纤通信的容量,以模式为自由度的模分复用技术应运而生。模分复用技术利用少模光纤中的高阶模式作为新的独立信道,成倍地提高了光纤通信系统的容量和传输效率。同时,光纤模式转换是利用模式耦合原理实现基模和高阶模的能量交换,是构建模分复用系统的关键技术之一,也是近年来的研究热点。光子晶体光纤因其灵活的结构设计性和和特殊的光学特性,广泛应用在光纤传输及光学器件的设计等领域。本文从实用化角度出发,设计了基于光子晶体光纤的少模传输光纤和模式转换器。利用麦克斯韦方程分析少模光子晶体光纤中的模式特性,利用波导耦合理论分析了模式转换的原理,为少模传输和模式转换器的实现提供了理论依据,论文的具体工作如下:本文首先针对长距离大容量光纤传输系统,从降低制作难度和提高实用性出发,设计了一种单芯的双模PCF。在1.46~1.56μm波长段内,该光纤可实现稳定的基模和二阶模的双模传输,模式间有效折射率差大于0.001,避免了模间串扰。通过优化结构得到Λ=10μm,d_1/Λ=0.55、d_2/Λ=0.65、d_3/Λ=0.75时,基模和二阶模在C波段上的相对色散系数分别为2.138ps/(nm·km)、1.154ps/(nm·km),色散斜率介于-0.012~0.322 ps/(nm~2·km)之间满足色散平坦要求;1.55μm处,模场面积分别为106.72μm~2和155.34μm~2;传输模式的衰减系数小于1.41×10~(-5)d B/m,总损耗小于10~(-4)量级。双模PCF的传输特性符合G.652和G.655光纤标准,且有效抑制了非线性效应,参考现有光纤成熟的制备技术,具有广阔的实用化前景。其次,针对模分复用技术中的模式转换问题,提出了一种基于PCF的模式转换器,实现了LP_(01)和LP_(11)模的低损耗转换。在1.50~1.56μm范围内,耦合效率可达92.93%,传输损耗小于1d B,并具有宽带特性。文中给出基于少模光子晶体光纤的模分复用系统结构模型,对相关技术问题做了论述。本文的研究均基于光子晶体光纤的特殊结构及特性,有利于新一代光纤通信技术的进一步研究和应用。
[Abstract]:In recent years, because of the small nonlinear tolerance of single-mode optical fiber, the transmission capacity of WDM system is closer to Shannon limit. In order to further expand the capacity of optical fiber communication, modular division multiplexing (DM) technology with Mode-Degree-of-Freedom (DOF) emerged as the times require. Mode division multiplexing (MWDM) uses high-order modes in low-mode optical fiber as a new independent channel, which can greatly improve the capacity and transmission efficiency of optical fiber communication system. At the same time, the mode conversion of fiber is one of the key technologies to construct the modular division multiplexing system, which realizes the energy exchange between the base mode and the high order mode by using the mode coupling principle, and is also the research hotspot in recent years. Photonic crystal fiber (PCF) is widely used in optical fiber transmission and optical device design due to its flexible structural design and special optical properties. In this paper, we design a low mode transmission fiber and mode converter based on photonic crystal fiber. Using Maxwell equation to analyze the mode characteristics in the photonic crystal fiber, and the waveguide coupling theory is used to analyze the principle of mode conversion, which provides a theoretical basis for the realization of the mode converter and the transmission of the less mode. The main work of this paper is as follows: firstly, a single-core dual-mode PCF is designed in order to reduce the fabrication difficulty and improve the practicability of the long distance and large capacity optical fiber transmission system. In the wavelength range of 1.46 渭 m and 1.56 渭 m, the fiber can achieve stable two-mode transmission of base mode and second-order mode. The effective refractive index difference between modes is greater than 0.001, thus avoiding crosstalk between modes. By optimizing the structure, the relative dispersion coefficients of the base mode and the second-order mode in C band are found to be 1.154 ps-1 / 0.55 ps/(nm~2 / 渭 m, respectively, and the dispersion slope between -0.0120.322 ps/(nm~2 km and 1.55 渭 m for the base mode and the second-order mode at C band, respectively, and the dispersion slope is between -0.0120.322 ps/(nm~2 km. the relative dispersion coefficients of the base mode and the second-order mode are 1.55 渭 m and 1.55 渭 m, respectively, and the dispersion slope is -0.0120.322 ps/(nm~2 / km, and the relative dispersion coefficients of the base mode and the second-order mode in C band are 1.154ps-1. The mode field area is 106.72 渭 m ~ (2) and 155.34 渭 m ~ (-2), respectively. The attenuation coefficient of transmission mode is less than 1.41 脳 10 ~ (-5) dB / m, and the total loss is less than 10 ~ (10) ~ (-4). The transmission characteristics of dual-mode PCF accord with G. 652 and G.655 fiber standards, and effectively suppress the nonlinear effect. Referring to the existing mature fabrication technology of fiber, it has a broad practical prospect. Secondly, a mode converter based on PCF is proposed to solve the mode conversion problem in mode division multiplexing technology. In the range of 1.50 ~ 1.56 渭 m, the coupling efficiency can reach 92.93, the transmission loss is less than 1dB, and it has broadband characteristics. In this paper, the structure model of module division multiplexing system based on low mode photonic crystal fiber is presented, and the related technical problems are discussed. The research in this paper is based on the special structure and characteristics of photonic crystal fiber, which is beneficial to the further research and application of the new generation optical fiber communication technology.
【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;TN929.11

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