光纤传输系统中高线性度模拟信号传输技术研究

发布时间：2018-08-05 12:55

【摘要】：光纤通信技术是现今通信行业甚至整个信息产业的热门技术之一。同时,也是通信技术未来发展的主要方向。为了能够适应现代通信技术向着高速率、大容量、低损耗的方向发展,光纤通信在商业、军事等领域都有着极高的地位和发展空间。模拟传输信号,在光纤中的传输充分利用了其低损耗,高传输速率的优势,引起了广泛的研究。因此,实现模拟信号的高线性度、低损耗传输是光纤传输系统中的关键技术之一。由于模拟信号在光纤传输中受到非线性损耗的影响较大,现有的方法中主要有两种方法用于减小其对系统性能的影响：一是简单地通过增加光学器件、改变传输系统自身结构来降低非线性损耗,但是这种方法只能在一定程度上降低非线性效应,未能提高信号增益；二是在光电相位调制的基础上,应用负反馈调节机制提高系统线性化程度。由于该方法是基于相位调制的传输方法,传输系统受相位影响很大,从而造成系统的不稳定。因此,为了克服这些缺陷,本论文围绕高线性、低损耗的光纤通信方法展开深入的分析。首先,系统的分析和总结了现有模拟信号光电通信技术的技术背景、调制和解调技术的基本概念、系统框架,以及光电传输技术的特点。基于现有的调制和解调方法：论文研究了一种调制器低偏置角度的光电传输方法。在传统强度调制的基础上,对调制器的最佳偏置角度进行推导和验证。推导得到的最佳偏置角度能够使得系统非线性程度最低,即：调制器工作在所推导的最佳偏置角度时,系统的动态杂散范围(SFDR, Spurious Free Dynamic Range)的数值达到最大,同时噪声指数(NF, Noise Figure)最小。相比传统正交偏置的强度调制而言,系统性能得到最大优化。同时,该方案给出了确保系统有效性的条件,即相对强度噪声(RIN, Relative Intensity Noise)必须大于17倍的传输激光器热噪声(Thermal Noise)。此外,论文针对基于相位调制的相干解调技术进行了深入的研究。针对该传输系统,进行了时域和频域的分析,推导得到了信号项和三阶互交调项的解析表达式,并通过数值仿真验证了其正确性。最后,在此基础上,论文首次提出了一种基于强度调制和负反馈解调的光纤通信方法。该方法在发送端,使用强度调制方式对载波光信号进行调制,而在接收端,使用光-电探测器实现对已调信号的解调,从而有效地解决了传统相位-相干解调系统中已调信号相位受温度影响较大的问题,即当温度变化较大时,已调信号的相位受外部环境影响而改变导致信号不稳定。因此在传统强度调制的链路基础上增加负反馈回路减少链路受环境影响的同时提高了传输信号质量,此外该方法克服了传统系统传输增益较低的缺陷。论文经过一系列的数学推导,得到了关于该系统传输性能的解析表达式,并通过与数值仿真结果相比较,验证了该解析表达式的准确性和该传输系统的性能优越性。
[Abstract]:Optical fiber communication technology is one of the hot technologies in the communication industry and even the whole information industry. At the same time, it is also the main direction of the future development of communication technology. In order to adapt to the development of high speed, large capacity and low loss in the direction of modern communication technology, fiber communication has a very high status and development in the fields of Commerce, military and other fields. In the optical fiber, the transmission of analog signals makes full use of the advantages of low loss and high transmission rate. Therefore, the realization of high linearity and low loss transmission of analog signals is one of the key technologies in the optical fiber transmission system. The simulation signal is greatly influenced by the nonlinear loss in the optical fiber transmission. In the existing methods, there are two main methods to reduce the effect on the performance of the system. One is to reduce the nonlinear loss by simply increasing the optical device and changing the structure of the transmission system, but this method can only reduce the nonlinear effect to a certain extent, and can not raise the high signal gain; two is in the photoelectric phase modulation. On the basis of this, the negative feedback regulation mechanism is applied to improve the degree of linearization of the system. Because the method is based on the phase modulation transmission method, the transmission system is affected by the phase greatly and thus causes the system instability. Therefore, in order to overcome these defects, this paper focuses on the high linear, low loss fiber communication methods. First, the method of optical fiber communication is analyzed. This paper analyzes and summarizes the technical background of the existing analog signal optical communication technology, the basic concepts of modulation and demodulation technology, the system framework and the characteristics of the photoelectric transmission technology. Based on the existing modulation and demodulation methods, the paper studies a photoelectric transmission method of low bias angle of the modulator. The optimal bias angle of the modulator is derived and verified. The obtained optimal bias angle can make the system minimum nonlinear, that is, the dynamic stray range (SFDR, Spurious Free Dynamic Range) of the system reaches the maximum when the modulator works at the optimal bias angle, and the noise index (NF, No) is at the same time. ISE Figure) is minimal. Compared with the traditional orthogonal bias intensity modulation, the system performance is optimized. At the same time, the scheme gives the condition to ensure the effectiveness of the system, that is, the relative intensity noise (RIN, Relative Intensity Noise) must be greater than 17 times the thermal noise of the transmission laser (Thermal Noise). Furthermore, the thesis is aimed at the phase based modulation. The coherent demodulation technology is deeply studied. The analysis of the time domain and frequency domain is carried out for the transmission system. The analytical expressions of the signal term and the three order cross modulation are derived, and the correctness is verified by the numerical simulation. Finally, on this basis, the paper first proposes a kind of intensity modulation and negative feedback demodulation. The method of optical fiber communication. This method uses the intensity modulation mode to modulate the carrier wave signal at the sending end, and the demodulation of the modulated signal is realized by the light electric detector at the receiving end. Thus, the problem that the phase of the modulated signal in the traditional phase coherent demodulation system is greatly affected by the temperature is effectively solved, that is, when the temperature varies greatly. When the phase of the modulated signal is affected by the external environment, the signal is unstable. Therefore, the negative feedback loop is added to the traditional intensity modulated link to reduce the link affected by the environment and improve the transmission signal quality. In addition, the method overcomes the shortcomings of the traditional system with low transmission gain. The analytical expression of the transmission performance of the system is obtained, and the accuracy of the analytical expression and the performance superiority of the transmission system are verified by comparison with the numerical simulation results.
【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN929.1

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