【作者】 李诺晗；

【导师】 潘炜；

【作者基本信息】 西南交通大学 ， 通信与信息系统， 2005， 硕士

【摘要】 随着通信新业务的发展,语音、图像、数据等信息量呈现快速增长趋势,这对网络传输容量和传输距离等提出了更高的要求。波分复用(WDM)或副载波复用(SCM)与掺铒光纤放大器(EDFA)的结合应用是充分挖掘光纤带宽能力,实现大容量、长距离、高速率通信的有效手段,因此研究复用信号放大过程的动态行为有着重要的理论和实践意义。 本文以复用信号放大过程的物理方程为基础,不同于以往的处理方法,采用电子元件刻画基于受激辐射机制的光信号放大行为,并引入传输线宏模型表征掺铒光纤延迟的影响,在国内首次分别构建出波分复用信号放大和含啁啾效应的副载波复用信号放大的等效电路模型,将电路级仿真方法扩展到复用信号放大特性的研究中。 借助所构建的等效电路模型,利用电路仿真软件PSPICE,分别实施了直流、瞬态和交流输入信号情形下的动态仿真,模拟了WDM信号放大过程中通道数目对瞬态效应的影响、多通道放大输出功率谱以及信号间串话特性。并进一步对SCM信号放大情形进行了研究,分析了系统的互调失真(IM2)和输出功率谱特性。仿真结果表明,调整泵浦功率值可抑制瞬态效应,提高调制频率可使串话减弱,减小激光器的频率啁啾或增大EDFA的输入光功率都可改善IM2。这些分析与结果对实际系统的设计和优化有一定参考价值,也表明了基于等效电路模型的电路级仿真是研究光电系统相关问题的一种有效途径。更多还原

【Abstract】 With the development of new communication services, the contents of information including voice, image and data increase quickly which bring a higher requirement for network’s transmission capacity and distance. The technology of wavelength division multiplexing (WDM) system or subcarrier multiplexing (SCM) system combined with erbium-doped fiber amplifier (EDFA) is an effective method to realize high capacity, long haul, high speed communications, and can take fully advantage of the optical fiber’s bandwidth. Therefore, studying on the dynamic behaviors of multiplexed signals in the amplification process has significant theoretical and practical meaning.In this paper, according to the basic physical equations of multiplexed signals in the amplification process, different from the traditional calculation methods, the electronic elements are adopted to describe the amplified behaviors of optical signals based on stimulated emission and the macro-model of transmission line is introduced to describe the time delay from the erbium-doped fiber. The equivalent circuit models of WDM signals and SCM signals including the chirping effect are established for the first time. Circuit-level simulation method is applied to investigate the amplified characteristics of multiplexed signals.Based on the equivalent circuit model, the dynamic simulations are implemented by performing the dc analysis, transient analysis and ac analysis through PSPICE. Typical characteristics are analyzed, including transient modulation, multi-channel output power spectrum and cross modulations of an eight-channel WDM. The intermodulation distortion and output power spectrum in an amplitude modulation SCM are demonstrated. The simulation results indicate that adjusting pump power properly can control transient effect, and increasing modulation frequency can weaken cross modulation, and decreasing frequency chirp of LD or enhancing the input power of signals can improve intermodulation distortion. These results will be useful for designing and optimizing the practical system and show that the method of circuit-level simulation based on circuit model is one of the effective methods in optoelectronic system simulations.更多还原