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基于平行排列3x3耦合器的双环全光缓存器的研究
Dual Loop Optical Buffer Based on Collinear 3x3 Fiber Coupler
【作者】 刘爱明；
【导师】 吴重庆；
【作者基本信息】 北京交通大学 ， 通信与信息系统， 2005， 博士
【摘要】 全光网是未来光纤通信网络的发展方向，全光包交换是全光网的一种优选技术，全光缓存器是全光包交换的重要基础元件。本文对基于平行排列3x3耦合器的各种缓存效应进行了研究，提出了两种基于平行排列3x3耦合器的全光缓存器方案，并对两种方案进行了理论和实验研究。研究结果表明横‘8’字型结构的双环全光缓存器(DLOB)具有更佳的稳定性，论文重点对两种不同非线性元件的DLOB进行了理论和实验研究，并就两种DLOB中的一些关键问题进行了深入的研究。论文取得的多项成果对于全光信息处理和全光包交换具有重要的理论价值和现实意义。 本文的主要创新工作包括下述几个方面： 1．分析了平行排列3x3耦合器不对称耦合情况下的输入输出特性，研究了它的偏振态演化和带宽特性，得出：不管从中间端口输入光的偏振态如何，经过这种耦合器后其演化比较小而且两侧输出端口的偏振态相同；分光比在40nm的波长范围内变化不超过5％。成功制作出了性能良好的国内首个平行排列3x3耦合器，测试结果验证了上述理论成果。 2．提出了～种基于平行排列3x3耦合器的正‘8’字型双环全光缓存器并对其稳定性进行了理论和实验研究，提出了一种反馈补偿方案来稳定正‘8’字型双环缓存器的输出。 3．提出了一种基于平行排列3x3耦合器的1x3三端口全光开关，它输出端口的其中两个具有相同的幅度和偏振态，可以用来构成DLOB。 4．提出了以SOA为非线性元件的DLOB，研究了它的缓存原理，设计和搭建了以SOA作为非线性元件的DLOB实验系统，首次得到了这种结构缓存器在信号速率为100Mb／s和2.5Gb／s下单个脉冲和16位数据帧的40m短环缓存实验结果。 5．提出了一种用来分析以SOA为非线性元件DLOB的噪声简化模型，在此模型的基础上研究了DLOB的背景噪声，首次得到了DLOB的背景噪声随着环路损耗的减小而急剧增大的公式与理论曲线以及实验结果。研究了DLOB输出信噪比随缓存圈数变化的关系，首次得到了不同条件下DLOB的输出信噪比随着缓存圈数变化的理论曲线，结果表明大信号输入和SOA处在低小信号增益时缓存器的噪声水平要低。提出了将控制光脉冲加上直流基座有效地抑制DLOB中噪声的技术方案。
【Abstract】 In the longer term, fiber communication network will go towards all-optical network and the bandwidth efficiency associated with optical packet switching will be required to ensure economic use of network resources. Optical buffer is one of most important element in optical packet switching network.This thesis reveals all kinds of buffering effects based on a collinear 3x3 fiber coupler, bringing forward two structures of optical buffer: recumbent ’8’ structure and upright ’8’ structure, called as Dual Loop Optical Buffer (DLOB). Theoretically and experimentally studies show, that DLOB with upright ’8’ structure is more stable than other. Two DLOBs with different nonlinear element are proposed, and especially key issues in them are inverstigated. A lot of results from this thesis are useful for all optical signal processing and all optical switching.The innovations of this thesis are as follows:1、 Studies on the collinear 3x3 fiber coupler which is the fundamental element of DLOB. Discovers how unsymmetricalness affect split ratio of the coupler and its broad-band and polarization maintained characteristics. Fabricates a collinear 3x3 fiber coupler with special split ratio.2、 Brings forward upright ’8’ structure buffer in which two loops are arranged like an upright digital number ’8’ and discusses its output stability. Designs feedback compensation method to stabilize the buffer’s output and examines its effect through experiment.3、 Brings forward a 3-port optical switch that is used as read/write control for DLOB and is the base of DLOB with two same-state ports.4、 Brings forward a DLOB in which SOA is used as the nonlinear element and studies the buffering principle in it. Devises its experiment system and carries out buffering experiment with a single pulse and a planed frame pattern at different bit rates. 5、 Brings forward a simple noise model and studies background noise in DLOB based on it. Studies the relationship between signal to noise ratio and loop circulations and get its theoretical curves. Brings forward a technical scheme to suppress the noise in DLOB by adding base onto control light pulse.