【作者】 张宝荣；

【导师】 郑德忠；

【作者基本信息】 燕山大学 ， 精密仪器及机械， 2010， 博士

【摘要】 在光纤性能测试以及各种应用中,经常需要测量微弱的光信号,如何有效精确地测量微弱的光信号也是许多光学系统所要解决的重要问题,研究新的检测方法是解决问题的关键。本文在现有文献的基础之上,将伪随机序列(PNs)应用到光学测量系统,利用伪随机序列的良好的随机性来检测淹没在噪声和干扰中的微弱光信号。论文对这种相关测量方法作了系统、深入的研究,主要工作如下:本文分析比较了各种伪随机序列的特性,讨论了各种序列的构造方法,改进了产生m序列的本原多项式的搜索算法,为产生不同周期的伪随机序列提供了理论基础。伪随机序列可以用来辨识系统的脉冲响应,将这种方法应用于光学测量系统,利用伪随机序列与系统输出之间的互相关峰值,可以测量出淹没在噪声与干扰中的信号的强度。使用理论分析与仿真的方法,分析了伪随机序列参数与测量性能之间的关系,结果表明测量系统的线性、测量误差以及信噪比增益都与伪随机序列的周期有关。为了消除各种干扰的影响,讨论了加权平均法的作用。为进一步测量输入信号的时域波形,论文讨论了扩频通信原理在微弱光信号测量系统中的应用。在频域上讨论了信号的扩频与解扩过程中信号以及噪声和干扰的频谱变化,用梳妆滤波器对伪随机序列进行滤波,然后再用其解扩,这种方法可以有效地消除各种频率的干扰信号,仿真检验了这种方法的测量精度。论文最后论述了基于伪随机序列的微弱信号测量系统的实验装置,完成了系统各部分的电路设计与调试并设计了信号处理程序。用这个实验系统测量了两类微弱信号,测量结果与理论分析结果基本符合,验证了基于伪随机序列的微弱光信号测量方法的有效性。伪随机序列用于微弱信号测量的研究内容十分广泛,在理论和实验两个方面都有深入研究的必要。在理论方面,需要进一步研究相关辨识理论和扩频原理的内在关系,使二者更加协调地联系起来,形成一个统一的相关测量理论。在实验方面,信号的产生与调制,信号的硬件处理都需要进一步完善和提高。更多还原

【Abstract】 It is a crucial problem that how to detect weak light signals accurately in the measurement of optical fiber performance and its applications or other optical systems. The key of the solution to this problem is to find some new detection methods. In this paper, on a base of many references, pseudo random sequences (PNs) were used in the optical measurement, weak light signals under strong interferences and noise background could be detected effectively using the nice randomness of pseudo random sequences. This correlation detection method was investigated in detail, studied systematically. The research works are as follows:In this paper, we have analyzed the characteristics of various pseudo random sequences, discussed all kinds of generation methods and improved on searching algorithm for primitive polynomials of m sequences. All above works provided a theoretical foundation for the generation of pseudo random sequences.The unit impulse response of a linear system could be distinguished by pseudo random sequences using correlation identification method. We applied this method to the optical measurement system. Through theoretical analysis and simulation, the relation between the performance of measurement and the parameters of PNs was shown that the linearity of system, mean square error and improvement factor of signal-to-noise ratio all were determined by the period of PNs. In order to eliminate various interferences, weighted average method was used.For detecting the time domain waveform of input signals, the principle of spread spectrum communication found its applications for an optical weak signal measurement system. All the varied spectrum of signals, interferences and noise were shown in the process of spreading and despreading. A pseudo random sequence after a comb filter for despreading removed the spectrum of interference from the range of signals, and therefore avoided harmonic interference. A simulation experiment verified the measurement accuracy using this method.Finally, the experimental devices of weak light signal measurement system based on pseudo random sequence were discussed at the end of this paper. We have finished the design and debug of all circuits and software in the system. Experimental results testing with two types of signals showed that the measurement accuracy was accordant to the theoretical analysis and this method was a valid method for the detection of weak light signals.There are many research works which need to be explored on the application of PNs to the detection of weak optical signals either in theory or on experiment. In theory, it is necessary to study the inherent relation between correlation identification and the principle of spread spectrum and to find a uniform correlative detection theory on weak signals. For experiments, there is a need for the improvement on signal generators modulation and the processing by hardware.更多还原