【作者】 齐海兵；

【导师】 余永林；

【作者基本信息】 华中科技大学 ， 电子科学与技术， 2011， 博士

【摘要】 可调谐滤波器是实现动态DWDM网络的关键器件之一,它不仅可以为接收机提供所要求的波长以建立完整的通信链路,而且可以与其他元件组合成智能、高效和稳定的功能模块,对提高动态DWDM网络的灵活性、改善网络性能和降低网络成本都具有重要意义。可调谐光纤法布里-珀罗(FFP)滤波器因具有带宽窄、调谐范围大和调谐速度快等优良特性而受到广泛地关注和研究。本论文围绕可调谐FFP滤波器的传输特性、调谐特性及波长跟踪锁定应用等方面展开了深入地研究,具体研究内容如下：(1)根据FP干涉仪中多光束干涉的基础理论,分析了插入损耗与峰值透射率和精细度的关系。并模拟分析了可调谐FFP滤波器的峰值透射率、线性直流电压驱动FP干涉仪的输出特性和交流正弦电压驱动洛仑兹谱线型滤波器的输出特性,为研究可调谐FFP滤波器奠定了理论基础。(2)理论研究了可调谐FFP滤波器的插入损耗。在无限镜面尺寸和有限镜面尺寸两种情况下,对空气隙腔型可调谐FFP滤波器中开腔的衍射损耗、镀膜镜面与单模光纤的模场耦合损耗进行了分析,结合开腔与单模光纤的模式失配损耗,完善了任意镜面尺寸时可调谐FFP滤波器的插入损耗分析理论。(3)提出了一种可调谐FFP滤波器的优化设计方案。在研究空气隙腔型可调谐FFP滤波器的峰值透射率与镜面尺寸对应关系的基础上,利用双向光束传输法模拟计算了不同条件下可调谐FFP滤波器的反射和透射谱特性,研究结果表明当镀膜镜面半径为光纤芯层半径的2～3倍时,插入损耗最小。因此提出了一种减小可调谐FFP滤波器插入损耗的结构设计方案。此外,还分析了波导空气隙腔混合型可调谐FFP滤波器中有限镜面尺寸对插入损耗和设计工艺的影响。(4)实验研究了可调谐FFP滤波器的静态调谐特性。在分析双峰测量、单峰测量、综合测量等三种测量方法的基础上,实验研究了静态调谐时可调谐FFP滤波器的腔长变化与线性驱动电压的关系。另外还探讨了可调谐FFP滤波器对动态相位调制信号的单边带和高次谐波的抑制作用。(5)利用信号处理领域的冲激响应不变法和傅里叶变换研究了可调谐FFP滤波器在调谐时的动态光谱和时域特性。仿真和测试结果表明：采用该方法得到的动态调谐特性不仅能通过可调谐FFP滤波器的光输出信号也能通过电输出信号确定动态响应与交流驱动信号参数的具体关系。(6)实验研究了可调谐FFP滤波器的动态调谐特性。通过在动态时域特性中引入PZT的延迟因子,提出了一种用于精确测量可调谐FFP滤波器相频特性的方法。实际测量了一种可调谐FFP滤波器的频域特性和谐振频率,给出了滤波器的工作频率范围。实验研究了不同幅度的阶跃函数激励下滤波器的阶跃响应,给出了滤波器透射信号不失真时的最大改变电压值。(7)针对波长扫描和自动跟踪锁定应用,研制了可调谐FFP滤波器的控制系统。通过分析开环系统中PZT的延迟时间和功率放大电路的控制时间以及闭环系统中积分滤波器的时间,提出了一种利用锁定时探测信号的理论时间分量与实际时间分量之差,计算波长锁定精度的方法。之后,采用单片机对控制系统进行了数字化改进设计。最后提出了一种基于FPGA和自适应滤波算法的数字控制系统设计方案。更多还原

【Abstract】 Optical tunable filters have been considered as one of critical components in dynamic dense wavelength division multiplexing (DWDM) networks. They can provide the required wavelength for the receiver to establish the communication links. Also they can be combined into intelligent, efficient and stable optical modules with other components. Therefore, they are helpful for the flexibility, efficiency and cost of the dynamic DWDM networks. Due to the advantages of narrow bandwidth, large tuning range and high tuning speed, tunable fiber Fabry-Perot (FFP) filters have attracted much attention. In this dissertation, optical transfer properties, tuning characteristics, wavelength tracking and locking applications of the tunable FFP filters have been investigated thoroughly. The main contents are as follows:(1) The relationship between the insertion loss and the peak transmission as well as the finesse of Fabry-Perot (FP) interferometer is analyzed based on the basic theories of the multiple beam interference. The peak transmissions of tunable FFP filters, the transfer property of FP interferometer driven by linear voltage, and the time domain response of the filter with Lorentizan spectrum driven by alternating voltage are derived are analyzed simulatedly. These can be considered as the theoretical basis to investigate e tunable FFP filters in the following chapters.(2) In the cases of infinite mirror size and finite mirror size of air gap type tunable FFP filter, the insertion losses (IL) including the diffraction loss and the mode field coupling loss between the fiber-mirror and the mode of single-mode fiber (SMF) are studied systematically. Combining with the mode mismatch loss between the air gap resonant mode and the mode of SMF regardless of the mirror optical boundary, the theory of IL of tunable FFP filer with arbitrary mirror size is supplemented.(3) A novel design of the tunable FFP filter is proposed. Based on analysis of the diffraction loss and the mode coupling loss between the mirror mode field and the mode of SMF, the optimum mirror size corresponding to the maximum peak transmission is obtained. The spectral properties of reflection and transmission are simulated by using a bi-directional beam propagation method for different situations of tunable FFP filters. And the results demonstrate that the IL of the FFP filter can be improved by selecting the fiber-mirror radius to be about 2-3 times of fiber-core radius. Therefore, a novel design for reducing the IL of the tunalble FFP filter is presented. Meanwhile, the effect of finite mirror size on the IL and practical factors of waveguide mixed air gap type tunable FFP filter are also simulated and analyzed.(4) Static tuning characteristics of a tunable FFP filter are investigated experimentally. The three methods of measuring the cavity length-voltage are compared including the peak-to-peak method, the two adjacent peaks method and the synthesis method. Static tuning characteristics of a tunable FFP filter are measured with the synthesis method. The effects of a tunable FFP filter on the side band and high frequency harmonics have been also investigated experimentally.(5) An impulse response method and Fourier transformation is proposed to theoretically analyze the dynamic characteristics of tunable FFP filter. The dynamic optical spectrum and time domain characteristic of a FFP tunable filter modulated by an alternating current (AC) dithering signal are derived. The simulated and experimental results show that the method can be used to determine the relation between the ac signal parameters and dynamic response through either the output optical signal or the output electrical signal.(6) Dynamic tuning characteristics of a tunable FFP filter are investigated experimentally. The phase frequency characteristics of tunable FFP filter is described by the dynamic time domain model by introducing a factor of PZT delay time, and a simple and accurate measuring method is propsed to measure the phase frequency of tunable FFP filter. And the frequency response including the phase frequency response and amplitude frequency response is measured. The resonant frequency and the working frequency range of the tunable FFP filter are determined. Instantaneous responses of tunable FFP filter with different amplitudes of step function are also measued and discussed.(7) For applications of wavelength scanning and locking, a controller of tunable FFP filter is designed. Through analysis of the time delay of open loop circuit and PZT, and the time constant of the closed-loop system, a wavelength measurement method utilizing the time difference between the theory time and measured time of the output signal is presented. The experimental results show that relative error of wavelength measurement is lower than the resolution ratio of optical spectrum analyzer at the scanning mode, and the preferable locking precision is obtained under the short-time stability with the designed wavelength controller. A digital controller based on MCU (Microcomputer Unit) for improvement is also designed. Finally we propose a design based on FPGA and adaptive filter algorithem.更多还原