【作者】 丁维银；

【导师】 蔡继光；

【作者基本信息】 华东师范大学 ， 光学， 2005， 硕士

【摘要】 在光纤通信中EDFA(掺铒光纤放大器)性能的某些缺陷会导致信号的失真。因此很有必要对EDFA进行增益均衡。本文提出了一种新颖的方法对EDFA的增益谱进行平坦:运用H-PDLC(聚合物分散液晶全息)光栅来平坦EDFA的增益谱,并利用光栅的电压可调特性实现动态增益均衡。文中首先由给定的EDFA的增益谱理论模拟出用于平坦的聚合物分散液晶全息光栅的参数,这一部分工作由Matlab语言编写程序利用遗传算法由计算机自动实现。光栅参数求得后可用于指导实验制作光栅,并可理论模拟由电压控制光栅的折射率调制度来实现EDFA的动态增益均衡。H-PDLC光栅作为动态增益均衡具有体积小、成本低、响应时间短、低功耗和平坦效果较好(增益平坦度小)等优点,是一种新颖的容易实现的方法,因此研究它具有很高的实用价值。理论模拟结果显示:运用该方法可在C-Band(1530-1560nm)内温度在0-65℃内变化增益平坦度达0. 2dBp-p。;波长在1525-1 565nm内温度在0-65℃内变化增益平坦度达0. 45dBp-p;波长在1 520-1 570nm内温度在0℃-65℃内变化增益平坦度达0. 5dBp-p。我们还进一步研究了厚光栅的耦合波理论,得到了H-PDLC光栅衍射效率的具体计算公式;实现了光栅衍射特性的基于Matlab语言的理论模拟;在实验方面研究了H-PDLC光栅在632. 8nm和1550nm光入射下的衍射特性;实验研究结果与理论比较后表明运用耦合波理论来解释光栅的衍射特性是恰当的。更多还原

【Abstract】 In fiber communications the shortcomings of EDFA (Erbium Doped Fiber Amplifier) maybe lead to the distortion. So it is necessary to equalize the gain spectrum. In the paper a novel method is presented that using the H-PDLC(Holographical- Polymer Dispersed Liquid Crystal) grating to flatten the gain spectrum and using the electro-optical properties of the H-PDLC grating to implement the dynamic equalization from to 0℃ to 65℃ have been successful in theory. Firstly the programs of Matlab language have been coded used GA to get the parameters of the grating to equalize the EDFA, then the parameters can guide the manufacture.The dynamic equalizer has much merit such as small volume, low cost, quick response, little power loss and good flatness. So the novel method that is easy to achieve has great practical value to study it. The results of the simulation have been got that on 1530~1560nm band-width from 0 ℃ to 65 ℃ the gain flatness has attained 0.2dBp-p, on 1525~1565nm band-width from 0℃ to 65℃the gain flatness has attained 0.45dBp_p and on 1520~1570nm band-width from 0℃ to 65℃ the gain flatness has attained 0.50dBp.p.On H-PDLC gratings, firstly the coupled-wave theory of the thick grating has been study, the formula to calculate the diffraction efficiency of the grating has been deduced and the characters of the grating have been simulated theoretically by Matlab language. Secondly the diffractive character of the grating incidence with the light of 632.8nm wavelength and 1550nm wavelength have been studied experimentally. Thirdly the electro-optical properties of the H-PDLC grating has been included.Finally the results of theory and experiment have been compared and the conclusion has been drawn that it is suitable to use the coupled-wave theory to explain the diffractive character of the grating.更多还原