利用速率方程分析光纤激光器相干耦合系统的尝试

尝试采用稳态速率方程,分析了由一个光纤耦合器连接起来的、两个掺Er光纤激光器组成的相干耦合系统.考虑到设置在光纤耦合器的一个输出端口的公共反射镜还担负着实施两个激光器间的相互注入的功能,利用光纤耦合器的变换矩阵以及光场相干叠加的要求,可以确定激光器速率方程组满足的边界条件.在进行合理的近似处理后,把速率方程组转化为代数方程组.利用这些结果分析了系统的一些特性,比如耦合器的分光比和不同泵浦功率对输出功率的影响等.     

利用偏振控制器连续调节光纤环镜的反射率

研究了一种新型光纤环镜(FLM)的原理与特性，这种FLM由在普通光纤环镜中插入光纤型偏振控制器(PC)构成.通过等效光路分析建立了该FLM的理论模型，并对其反射特性进行了数值模拟.研究表明，通过改变PC的状态，即改变其双折射效应的快轴取向或强度，可连续调节FLM的反射率，反射率谱具有宽带特性，主要受光纤耦合器工作带宽的影响.此外，对FLM的反射特性还进行了实验研究.实验结果也证实，通过调节PC状态，FLM反射率可在其最大和最小值之间连续调节，实验测得FLM最大和最小反射率分别可达93%和2%.根据PC双折 关键词： 光纤环镜 偏振控制器 光纤耦合器 反射率     

Analysis of Coupling and Radiation Properties for an Improved Dielectric Waveguide Directional Coupler Utilizing a Tapering Left-Handed Slab Core

The coupling and radiation characteristics of an improved dielectric waveguide directional coupler with a tapering left-handed slab core located in the coupling region are analyzed by the staircase approximation method, which combines the building block approach and multi-mode network theory with a rigorous mode-matching procedure. Particular attentions are directed toward the radiation characteristics under different structural parameters of the coupler. Numerical results indicate that the proposed coupler is very promising by shortening the coupling length significantly while keeping the radiation loss at a low level.     

A numerical model of multimode fiber PON frequency response

Frequency response of passive optical network (PON) based on multimode fibers is investigated. The network comprises fibers, connectors and splitters/couplers. It is shown that due to mode filtering at splitters, the frequency response is different for different network nodes in otherwise symmetrical network.     

一种双频微波功率合成器的设计与实现

一种新型的双频微波功率合成器，通过阶跃阻抗低通滤波器和平行耦合线带通滤波器构成的微带电路实现。该微波功率合成器实现了915MHz和2．5GHz两个非相干频率微波信号的功率合成。同时通过附加工作在915MHz和2．5GHz的20dB微带定向耦合器，就可以构建实验系统进行微波功率合成的测量。实验测量结果与数值模拟结果吻合，双频微波功率合成器和定向耦合器的性能达到了要求，可用于注入式微波器件效应的研究。     

Characteristics of a Grating-Folded Optical Directional Coupler

We developed a new optical add/drop multiplexer composed only of a grating-folded directional coupler. We found that in this multiplexer, the power drop becomes maximal when the grating-coupling strength is equal to that of directional coupling. At this maximum power, both power transfer between the waveguides and power reflection take place simultaneously at the grating. The power drop approaches 1 when the grating length increases.     

Analysis of Ti:LiNbO3 zero-gap directional coupler for wavelength division multiplexer/demultiplexer

For the purpose of multichannel integrated-optical wavelength division MUX/DEMUX design, the wavelength tuning method of Ti:LiNbO₃ zero-gap directional coupler is analysed by effective-index based matrix method (EIMM). In this method, first, the 2D refractive index profile of the Ti:LiNbO₃ zero-gap directional coupler is transformed into lateral 1D effective-index profile by WKB method. Finally, matrix method is applied to this effective-index profile and the propagation constants are computed from the resonance peaks of the excitation efficiency versus propagation constant characteristics. It has been shown that the channel wavelength tuning can be achieved by varying the Y-branching angle at the input and output of the device or by a slight variation of two-mode-section length. The method of electro-optic fine tuning of the channel wavelength and channel separation of the device has also been investigated. A cascaded structure with proper parameters for four-channel application is also simulated and the results are presented.     

3dB带状线电桥的研究与设计

首先对90°电桥进行了分析。提出一种特殊结构的宽带3dB电桥的设计方案。该方案可使电桥方向性更好、制作工艺更加简便,其带宽可达到9～11GHz,可以承受较大的功率容量,体积小,新式结构使其实现了低插损、高方向性和宽频带,并且易生产、易调试。实测结果和仿真结果基本吻合,验证了研究结果的一致性。     

全光纤马赫-曾德尔干涉仪型不等带宽梳状滤波器

提出了由2个3×3和1个3×3单模光纤耦合器级联组成的全光纤Mach-Zehnder干涉仪(MZI)型不等带宽交错(梳状)滤波器。分析结果表明:两对光纤干涉臂长度差相等时,各耦合器的耦合系数选取适当值,器件实现了奇偶信道上不等带宽输出,分别用于10和40Gb/s传输,信道间隔为0.8nm,信道隔离度大于25dB。与其它不等带宽梳状滤波器相比,该器件基于MZI型梳状滤波器,且在实际制作时可以对每个耦合器的分光比进行准确监测和控制,大大降低了制作困难。实验所得结果与理论分析相吻合。     

布拉格光栅辅助型上下话路滤波器的实验制作

采用波长为248nm的紫外光,在由标准单模光纤和自制的高掺锗光敏光纤熔融拉锥制作的2×2光纤失配耦合器上写入光纤光栅,实现了全光纤布拉格光栅(FBG)辅助失配耦合器型上下话路滤波器,并测试了器件的传输特性,器件的插入损耗和回波损耗分别为6.74dB和-18.84dB。用10Gbps的光信号进行了传输实验,分别测试了下话路前、后信号的眼图。与输入信号相比,下话路信号的信噪比从10.04dB降低到了9.27dB,信号的消光比从8.89dB降低到了4.68dB。