低噪声、高增益、高平坦度掺铒光纤放大器的分析与实验研究
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摘要
掺铒光纤放大器(EDFA)是光纤通信系统中的关键器件，它和密集波分复用(DWDM)技术的紧密结合是当前通信技术的发展主流。随着光纤通信向全光高速网络系统的深入发展，传统的C-band EDFA的增益带宽已经不能满足DWDM系统的要求，而且这种以均匀展宽为主的EDFA会随网络的动态重构引起进入EDFA的信道的增益不断变化从而影响系统的工作稳定性。开发新的L-band EDFA是十分必要的，然而传统的L-band EDFA由于工作在铒光纤增益谱的尾部，其存在增益低、工作转换效率低、噪声大等缺点，因此，分析和设计符合DWDM系统发展要求的具有优良性能(高增益、低噪声、动态增益均衡)的L-band EDFA是十分有意义的。
本论文本着科技创新、服务于生产实践的精神，以设计价格低廉，性能优越、结构合理简单的L-band EDFA为目标，依托浙江省科技厅重大科学基金资助项目(001101027)和浙江大学振兴教育计划资助的全光网络的搭建—《光通信技术》课程实验建设项目，展开了如下工作：
首先，介绍了掺铒光纤放大器的工作原理，归纳总结了基于速率方程基础的EDFA的各种理论模型，分析比较了各个模型的特点和适用场合，最终选择完善的Giles理论模型作为本论文分析设计EDFA的理论基础；针对实际实验条件提出了修正的EDFA模型的数值计算方法；创新地提出了增益—噪声系数全局分析法，直观有效地分析了EDFA的增益和噪声系数与掺铒光纤长度和泵浦功率的依赖关系，并对各种EDFA的性能作了全面的比较；
第二，介绍了掺铒光纤放大器特性参数的定义与测量方法，重点介绍了噪声系数和增益系数的测量方法及实验装置；介绍了组成掺铒光纤放大器各组件的特性测量方法，重点介绍了测量掺铒光纤(EDF)参数的方法和实验装置；
第三，针对WDM系统对L-band EDFA谱平坦、低噪声、高增益的要求，我们创新地提出了四种不同的L-band EDFA结构，按设计思路可以分为两大类：一类是基于单抽运二级泵浦法，这一类包括(a)在未泵浦掺铒光纤的输入端插入一根布拉格光纤光栅的两段L-band的EDFA的新结构；(b)基于前向ASE光作为二级泵浦源推动下一级EDF工作的泵浦分配、两段级联L-band的EDFA的新结构；(c)基于单根光纤光栅、泵浦分配、两段级联的EDFA；另一类则是基于同时应用前后向C-band ASE作二级泵浦源的双抽运法，如(d)基于前后向ASE光作为二级泵浦源的三段级联L-band的EDFA的新结构。文中从理论上系统分析设计了结构参数对各种EDFA性能的影响，最后通过实验验证；
第四，针对波分复用系统要求EDFA必须具备增益锁定功能，提出采用单根光纤光栅的方法来箝制L-band EDFA的增益。基于考虑自发辐射噪声(ASE)的Giles模型，建
浙江大学博士学位论文
立了这种EDFA的全光增益箱制理论模型;理论和实验分析了四种可能的光路结构、泵
浦波长、光纤光栅反射波长和反射率、泵浦功率以及掺饵光纤长度等参t对其箱制特性
的影响。最后给出一组使EDFA在箱制增益的同时可以保持增益谱平坦的最佳结构和放
大器参量;
最后，初步介绍了光纤的非线性效应的产生机理及其对光通信系统的影响;实验研
究了应用EDFA测t布里渊散射阐值的实验装置与方法。
总之，本论文围绕光纤通信领域的国际热点问题，从理论和实验上研究了高增益、
低噪声、谱平坦的掺饵光纤放大器的实现，关于EDFA的特性的研究成果，我们相信能
对科研生产起一定的指导作用。
Erbium doped fiber amplifier (EDFA) is a key part in an optical fiber communication system. Combined with the dense wavelength division multiplexing (DWDM) technology, optical fiber amplifier is the current trend of optical fiber communication. With the rapid growth of all-optical and high-speed networks, the gain bandwidth of a conventional C-band EDFA cannot satisfy the requirement of a DWDM system. Furthermore, the gain of each channel will change dynamically with the network reconfiguration for a uniformly broadened EDFA, which will finally influence the stability of the communication system. It is thus of importance to develop an L-band EDFA. However, a conventional L-band EDFA is relatively inefficient and has low gain and high noise figure since they are operated at the tail of the erbium gain band. Therefore, it is very important to design and analyze a high performance L-band EDFA with simultaneously high gain, low noise and low gain ripple for a DWDM system.
With the support of a major research grant of Zhejiang Province (No. 001101027) and the Plan of Promoting Education of Excellence of Zhejiang University in the 21st Century, this dissertation is devoted to address the above problems and fabricate an L-band EDFA with low cost, high performance and technological innovation.
First the mechanism of an erbium doped fiber amplifier is introduced. Various theoretical models based on classical rate propagation equations are summarized and compared for their applications. We use a modified numerical model based on the Giles model, which agrees with the experimental results well. This serves as the theoretical base for the whole thesis and will be used to optimize the characteristics of EDFAs. A novel method based on a map of noise figure and gain is proposed to analyze efficiently the dependence of the noise figure and gain for EDFAs on the EDF length and the pump power. The characteristics of various EDFAs are studied and compared.
Secondly, some important parameters are introduced to describe the characteristics of EDFAs. The methods and the experimental setups for measuring the gain and noise figure of an EDFA are emphasized. We introduce how to measure the characteristics of each component of an EDFA, especially the gain and absorption coefficient of an erbium doped fiber (EDF).
Thirdly, four types of simple and novel L-band EDFA structures with low noise, high gain and low gain ripple are proposed to satisfy the requirement of a DWDM system. They can be classified into two categories. In the first category, a single ASE pumping is served as
a secondary pump. This category includes the following three types. Type (a): a new construction using a fiber Bragg grating (FBG) in an unpumped EDF section at the input side. Type (b): a new structure of L-Band EDFA with two-stage pumps, which utilizes the forward ASE as a second pump. Type (c): a new two-stage, pump-allocated L-band EDFA structure with a single fiber grating. The second category is to use double ASE pumps. For example, Type (d): a novel three-stage L-band EDFA with very large and flat gam and very low noise presented in this thesis. It uses the forward ASE from the first section of the EDF and the backward ASE from the third section of the EDF (both serve as the secondary pump) to pump the second EDF. Note that all these structures are numerically simulated firstly and then verified by the experiments.
Fourthly, in accordance with the need of gain control in a wavelength division multiplexed system, a gain-clamped L-band EDFA using a single fiber Bragg grating (FBG) is proposed. Based on the Giles Model with ASE, numerical simulation for the all-optical gain-clamped EDFA is carried out. The influence of the configuration, the pump wavelength, the Bragg wavelength, the reflectivity, the pump power and the length of EDF to the gain-clamped characteristics is studied. An optimal L-band gain-clamped EDFA configuration with appropriate parameters of the amplifier, which can also provide a flat-gain band, are given.
Finally, the mechan
本论文本着科技创新、服务于生产实践的精神，以设计价格低廉，性能优越、结构合理简单的L-band EDFA为目标，依托浙江省科技厅重大科学基金资助项目(001101027)和浙江大学振兴教育计划资助的全光网络的搭建—《光通信技术》课程实验建设项目，展开了如下工作：
首先，介绍了掺铒光纤放大器的工作原理，归纳总结了基于速率方程基础的EDFA的各种理论模型，分析比较了各个模型的特点和适用场合，最终选择完善的Giles理论模型作为本论文分析设计EDFA的理论基础；针对实际实验条件提出了修正的EDFA模型的数值计算方法；创新地提出了增益—噪声系数全局分析法，直观有效地分析了EDFA的增益和噪声系数与掺铒光纤长度和泵浦功率的依赖关系，并对各种EDFA的性能作了全面的比较；
第二，介绍了掺铒光纤放大器特性参数的定义与测量方法，重点介绍了噪声系数和增益系数的测量方法及实验装置；介绍了组成掺铒光纤放大器各组件的特性测量方法，重点介绍了测量掺铒光纤(EDF)参数的方法和实验装置；
第三，针对WDM系统对L-band EDFA谱平坦、低噪声、高增益的要求，我们创新地提出了四种不同的L-band EDFA结构，按设计思路可以分为两大类：一类是基于单抽运二级泵浦法，这一类包括(a)在未泵浦掺铒光纤的输入端插入一根布拉格光纤光栅的两段L-band的EDFA的新结构；(b)基于前向ASE光作为二级泵浦源推动下一级EDF工作的泵浦分配、两段级联L-band的EDFA的新结构；(c)基于单根光纤光栅、泵浦分配、两段级联的EDFA；另一类则是基于同时应用前后向C-band ASE作二级泵浦源的双抽运法，如(d)基于前后向ASE光作为二级泵浦源的三段级联L-band的EDFA的新结构。文中从理论上系统分析设计了结构参数对各种EDFA性能的影响，最后通过实验验证；
第四，针对波分复用系统要求EDFA必须具备增益锁定功能，提出采用单根光纤光栅的方法来箝制L-band EDFA的增益。基于考虑自发辐射噪声(ASE)的Giles模型，建
浙江大学博士学位论文
立了这种EDFA的全光增益箱制理论模型;理论和实验分析了四种可能的光路结构、泵
浦波长、光纤光栅反射波长和反射率、泵浦功率以及掺饵光纤长度等参t对其箱制特性
的影响。最后给出一组使EDFA在箱制增益的同时可以保持增益谱平坦的最佳结构和放
大器参量;
最后，初步介绍了光纤的非线性效应的产生机理及其对光通信系统的影响;实验研
究了应用EDFA测t布里渊散射阐值的实验装置与方法。
总之，本论文围绕光纤通信领域的国际热点问题，从理论和实验上研究了高增益、
低噪声、谱平坦的掺饵光纤放大器的实现，关于EDFA的特性的研究成果，我们相信能
对科研生产起一定的指导作用。
Erbium doped fiber amplifier (EDFA) is a key part in an optical fiber communication system. Combined with the dense wavelength division multiplexing (DWDM) technology, optical fiber amplifier is the current trend of optical fiber communication. With the rapid growth of all-optical and high-speed networks, the gain bandwidth of a conventional C-band EDFA cannot satisfy the requirement of a DWDM system. Furthermore, the gain of each channel will change dynamically with the network reconfiguration for a uniformly broadened EDFA, which will finally influence the stability of the communication system. It is thus of importance to develop an L-band EDFA. However, a conventional L-band EDFA is relatively inefficient and has low gain and high noise figure since they are operated at the tail of the erbium gain band. Therefore, it is very important to design and analyze a high performance L-band EDFA with simultaneously high gain, low noise and low gain ripple for a DWDM system.
With the support of a major research grant of Zhejiang Province (No. 001101027) and the Plan of Promoting Education of Excellence of Zhejiang University in the 21st Century, this dissertation is devoted to address the above problems and fabricate an L-band EDFA with low cost, high performance and technological innovation.
First the mechanism of an erbium doped fiber amplifier is introduced. Various theoretical models based on classical rate propagation equations are summarized and compared for their applications. We use a modified numerical model based on the Giles model, which agrees with the experimental results well. This serves as the theoretical base for the whole thesis and will be used to optimize the characteristics of EDFAs. A novel method based on a map of noise figure and gain is proposed to analyze efficiently the dependence of the noise figure and gain for EDFAs on the EDF length and the pump power. The characteristics of various EDFAs are studied and compared.
Secondly, some important parameters are introduced to describe the characteristics of EDFAs. The methods and the experimental setups for measuring the gain and noise figure of an EDFA are emphasized. We introduce how to measure the characteristics of each component of an EDFA, especially the gain and absorption coefficient of an erbium doped fiber (EDF).
Thirdly, four types of simple and novel L-band EDFA structures with low noise, high gain and low gain ripple are proposed to satisfy the requirement of a DWDM system. They can be classified into two categories. In the first category, a single ASE pumping is served as
a secondary pump. This category includes the following three types. Type (a): a new construction using a fiber Bragg grating (FBG) in an unpumped EDF section at the input side. Type (b): a new structure of L-Band EDFA with two-stage pumps, which utilizes the forward ASE as a second pump. Type (c): a new two-stage, pump-allocated L-band EDFA structure with a single fiber grating. The second category is to use double ASE pumps. For example, Type (d): a novel three-stage L-band EDFA with very large and flat gam and very low noise presented in this thesis. It uses the forward ASE from the first section of the EDF and the backward ASE from the third section of the EDF (both serve as the secondary pump) to pump the second EDF. Note that all these structures are numerically simulated firstly and then verified by the experiments.
Fourthly, in accordance with the need of gain control in a wavelength division multiplexed system, a gain-clamped L-band EDFA using a single fiber Bragg grating (FBG) is proposed. Based on the Giles Model with ASE, numerical simulation for the all-optical gain-clamped EDFA is carried out. The influence of the configuration, the pump wavelength, the Bragg wavelength, the reflectivity, the pump power and the length of EDF to the gain-clamped characteristics is studied. An optimal L-band gain-clamped EDFA configuration with appropriate parameters of the amplifier, which can also provide a flat-gain band, are given.
Finally, the mechan
引文
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[2] 吴凤修．光扩容技术[J]．现代通信，1997，1：6-7．
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