基于少模光纤布拉格光栅的高阶模式获取技术研究

发布时间：2018-10-17 18:46

【摘要】：在过去的几年内,由于互联网技术、物联网技术以及IPTV等技术的蓬勃发展,通信业务需求出现了爆发式的增长。人们为了避免“带宽耗尽”局面的发生,提出了诸如波分复用技术、偏振复用技术以及正交频分复用技术等多种新型通信技术来提高现有单模光纤系统的通信容量。然而随着信号传输速率的提升,系统对于光信噪比的要求越来越高,单模光纤中的非线性效应对系统性能的影响也日益突出。在这种形势下,基于少模光纤的模式复用技术应运而生,顾名思义,模式复用就是利用少模光纤中相互正交的各个传播模式作为独立的信道,并复用到同一根少模光纤内进行传输。由于开辟了模式这一新的通信自由度,模式复用技术将会成倍的提升现有通信系统的传输容量;同时,少模光纤的模场面积相对较大,因此模式复用技术对于光纤非线性效应的容忍度也非常优秀,模式复用技术将是未来光通信领域的关键技术之一。在模式复用技术中,高阶模式获取器件的性能对于系统有着至关重要的影响,然而现有的各类高阶模式获取器件并不能很好的满足商用通信系统的需求。在此背景下,本文对模式复用技术中的高阶模式获取技术进行了深入的研究,提出了一种基于少模光纤布拉格光栅的高阶模式获取技术,利用少模光纤布拉格光栅能够在布拉格波长上反射特定高阶模式的特性,使用与少模光栅反射谱中特定高阶模自耦合谐振峰相匹配的光纤激光器作为光源,并结合光环行器,便可在少模光纤布拉格光栅的反射端获取目标高阶模式。本文中的具体工作如下所示:首先我们对少模光纤中的传播模式理论进行了推导,从Maxwell方程组出发得到光纤中的波动方程,并通过标量法对其进行近似求解,以此对光纤中模式的传播特性进行了分析,该工作为文中后续的内容奠定了基础。然后对现有模式复用技术中使用的高阶模式获取器件的工作原理进行了介绍,分析了各类高阶模式获取器件的优势与不足,并且对基于倏逝波耦合的非对称波导型高阶模式获取技术进行了仿真研究。接着在第3章中,我们从光纤光栅的制作、分类和应用角度出发,对光纤光栅技术的整体情况进行概述。然后以耦合模理论为工具,对少模光纤布拉格光栅的特性进行了理论研究,并且仿真分析了少模光纤布拉格光栅各个反射峰的模式传输特性。使用相位掩模法蚀刻光纤光栅时采用单侧曝光会导致的纤芯横向折射率的不均匀分布,我们分析了该效应对少模光纤布拉格光栅传输特性的影响。最后我们以双模光纤布拉格光栅为例,搭建了实验系统对其3个反射谐振峰的模式传输特性进行了研究。最终利用这些特性成功的获取了 LP11模式,并通过调整单模光纤与双模光纤之间的偏心熔接距离对LP11模式的插入损耗进行了优化。最后提出了适用于任意高阶模式的少模光纤布拉格光栅高阶模式获取技术,对其性能进行了综合的评价,并对以后的研究提出了建议。
[Abstract]:In the past few years, due to the rapid development of Internet technology, Internet of Things technology, IPTV and other technologies, the demand for communication services has experienced explosive growth. People are trying to avoid "Bandwidth depletion" Several new communication technologies, such as wavelength division multiplexing technology, polarization multiplexing technology and orthogonal frequency division multiplexing technology, have been proposed to improve the communication capacity of the existing single-mode optical fiber system. However, with the increase of signal transmission rate, the system has higher requirements on optical signal-to-noise ratio, and the nonlinear effect in single-mode fiber is more and more prominent. In this situation, the mode multiplexing technology based on the small-mode optical fiber has emerged, and the mode reuse is the independent channel by using each propagation mode orthogonal to each other in the low-mode optical fiber, and is multiplexed into the same small-mode optical fiber for transmission. Due to the opening of the new communication freedom degree of the mode, the mode multiplexing technology will multiply the transmission capacity of the existing communication system in multiple times, and meanwhile, the mode field area of the small-mode optical fiber is relatively large, so that the mode multiplexing technology is very good for the nonlinear effect of the optical fiber, Mode multiplexing technology will be one of the key technologies in the field of future optical communication. In the mode reuse technology, the performance of the high-order mode acquisition device is very important to the system, however, the existing high-order mode acquisition devices do not meet the requirements of the commercial communication system very well. In this context, this paper deeply studies the high-order mode acquisition technology in the mode reuse technology, and puts forward a high-order mode acquisition technology based on the small-mode fiber Bragg grating. An optical fiber laser matched with a specific high-order mode self-coupling resonant peak in a low-mode grating reflection spectrum is used as a light source and combined with an optical circulator, the target high-order mode can be obtained at the reflection end of the low-mode fiber bragg grating. The concrete work in this paper is as follows: Firstly, we derive the propagation mode theory in the small-mode optical fiber, derive the wave equation in the optical fiber from the Maxwell equations, and approximate the propagation characteristic of the optical fiber by the scalar method, and then analyze the propagation characteristics of the mode in the optical fiber. This work laid the foundation for the follow-up to the text. Then the operation principle of the high-order mode acquisition device used in the existing mode multiplexing technology is introduced, the advantages and disadvantages of the high-order mode acquisition devices are analyzed, and the simulation research is carried out on the asymmetric waveguide-type high-order mode acquisition technology based on the evanescent wave coupling. Then, in chapter 3, we give an overview of the overall situation of fiber grating technology from the viewpoint of fabrication, classification and application of fiber grating. Then, based on the coupled mode theory, the characteristics of the low-mode fiber Bragg grating are studied theoretically, and the mode transfer characteristics of the reflection peaks of the low-mode fiber Bragg gratings are analyzed. The influence of this effect on the transmission characteristics of fiber Bragg gratings is analyzed. At last, the mode transmission characteristics of three reflection resonance peaks in the experimental system are studied by using the dual mode fiber Bragg grating as an example. Finally, LP11 mode is obtained successfully with these characteristics, and the insertion loss of LP11 mode is optimized by adjusting the eccentric fusion distance between single-mode fiber and dual-mode fiber. At last, the high-order mode acquisition technology for the low-mode fiber Bragg grating suitable for arbitrary high-order modes is put forward, the performance of the high-order mode acquisition technology is comprehensively evaluated, and the future research is put forward.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN253;TN929.11

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