光纤激光拍频技术用于色散测量的研究

发布时间：2018-03-07 06:21

本文选题：色散测量　切入点：光纤激光器　出处：《河南师范大学》2017年硕士论文　论文类型：学位论文

【摘要】：色散测量是光纤通信系统中提高通信质量的重要环节。作为光纤的一个非常重要的光学参数,色散会造成光纤中传输的光信号发生脉冲展宽,引起误码现象,导致光信号传输畸变,严重影响信息传输的正常运行,因此色散成为了现代通信中扩大通信容量和增大中继通信距离的最大障碍。通常会采用色散补偿的方法来补偿信号在光纤传输过程中产生的色散。但是色散补偿的前提是对光纤色散准确的测量,这样才有助于光通信中色散的有效管理。本文提出了一种基于多纵模拍频解调测量光纤色散的方法。相比其他传统的色散测量方法,这种方法采用拍频信号作为解调信号,把光信号转换为电信号进行处理,操作更简单,且用来检测的仪器仅为光电探测器和频谱分析仪,成本较低,具有较好的发展前景。首先,详细介绍了几种常见的用来测量光纤色散的方法,并分析了它们各自的优点和不足。回顾了拍频解调技术用于光纤传感领域的应用历程,分析了拍频解调的优势所在。然后,介绍了光纤激光器的发展背景和独特优点。和传统的激光器相比,光纤激光器一样是由增益介质、光学谐振腔和泵浦源三部分构成,但体积更小、结构更简单、光束质量更好、泵浦效率更高、易实现单模单频运转以及成本更加低廉等优点使得光纤激光器应用领域非常广泛。详细介绍了光纤激光器的结构,掺铒光纤的三能级结构以及激光产生的工作原理。介绍了光纤谐振腔内的纵模的概念、产生的过程及模式选择的常见方法,并分析了激光多纵模拍频产生的机制。最后综合分析归纳了稳定激光拍频的影响因素。最后,结合色散补偿光纤和普通单模光纤的背景知识,基于光纤激光器,提出了一种利用拍频解调测量光纤色散的实验设计。光纤谐振腔的两个反射镜分别为:由光纤耦合器通过一端的两条支路相互熔接构成环路组成的Sagnac环,由光纤环形器和光纤可调谐FP滤波器组合成的光纤环形反射镜。文中详细分析了色散测量的基本原理,通过计算得到最佳的观测拍频频率,以便提高测量的精度。以500m色散补偿光纤和3.636 km普通单模光纤作为待测光纤,详细介绍了实验测量的过程,通过数据处理分别得到了色散补偿光纤和普通单模光纤的色散系数,测量的结果与厂家提供参考值基本符合。综合多方面的因素分析了实验测量的误差。本文利用实验证明了基于激光拍频测量光纤色散方案的可行性,且测量方法简单,测试系统成本低,为色散的测量提供了一些参考价值。
[Abstract]:Dispersion measurement is an important part of improving communication quality in optical fiber communication system. As a very important optical parameter of optical fiber, dispersion will cause pulse broadening of optical signal transmitted in optical fiber and cause error code phenomenon. Causing distortion of optical signal transmission, seriously affecting the normal operation of information transmission, Therefore, dispersion becomes the biggest obstacle to enlarge communication capacity and increase relay communication distance in modern communication. Dispersion compensation is usually used to compensate the dispersion produced by the signal in the process of optical fiber transmission, but dispersion compensation is used to compensate the dispersion. The premise is an accurate measurement of the dispersion of the optical fiber, This method is helpful to the effective management of dispersion in optical communication. In this paper, a method of measuring fiber dispersion based on multi-longitudinal-mode beat frequency demodulation is proposed. Compared with other traditional dispersion measurement methods, this method uses beat frequency signal as demodulation signal. The conversion of optical signals to electrical signals for processing is simpler, and the instruments used for detection are only photodetectors and spectrum analyzers, which have low cost and have a good prospect of development. Several common methods used to measure fiber dispersion are introduced in detail, and their respective advantages and disadvantages are analyzed. The application of beat frequency demodulation in the field of optical fiber sensing is reviewed, and the advantages of beat frequency demodulation are analyzed. The development background and unique advantages of fiber laser are introduced. Compared with traditional laser, fiber laser is composed of gain medium, optical resonator and pump source, but it is smaller, simpler in structure and better in beam quality. The advantages of high pump efficiency, easy to realize single-mode single-frequency operation and lower cost make the application field of fiber laser very wide. The structure of fiber laser is introduced in detail. The three-level structure of erbium-doped fiber and the working principle of laser generation are introduced. The concept of longitudinal mode in fiber resonator, the process of generation and the common methods of mode selection are introduced. Finally, the influence factors of stable laser beat frequency are analyzed and summarized. Finally, combining with the background knowledge of dispersion compensation fiber and ordinary single-mode fiber, the laser is based on fiber laser. An experimental design of optical fiber dispersion measurement using beat frequency demodulation is presented. The two mirrors of the fiber resonator are: a Sagnac loop composed of two branches of fiber coupler via one end to form a loop. The optical fiber annular mirror composed of fiber circulator and fiber tunable FP filter is presented. The basic principle of dispersion measurement is analyzed in detail, and the optimum beat frequency is obtained by calculation. Using 500m dispersion compensation fiber and 3.636km ordinary single-mode fiber as the fiber to be tested, the process of experimental measurement is introduced in detail. The dispersion coefficients of dispersion compensation fiber and ordinary single-mode fiber are obtained by data processing, respectively. The measurement results are in good agreement with the reference values provided by the manufacturer. The error of the experimental measurement is analyzed by synthesizing many factors. The feasibility of the scheme of optical fiber dispersion measurement based on laser beat frequency is proved in this paper, and the measurement method is simple. The low cost of the test system provides some reference value for dispersion measurement.
【学位授予单位】：河南师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN253;TN929.11

【参考文献】