高性能三端口全光纤开关

提出采用２×２和３×３单模光纤耦合器组合成的马赫－陈德尔干涉仪来制作全光纤开关。解决了在连续熔融拉伸两个耦合器组成马赫－陈德尔干涉仪的过程中，由于干涉的作用而无法监视光功率来控制第二个耦合器的分束比的问题。并且由于是连续熔融拉伸，保证了两条单模光纤干涉臂长度的一致，从而提高了单模光纤马赫－陈德尔干涉仪的性能，使得用其做成的三端口压电陶瓷电控全光纤开关具有宽频带的特性，其最小交调达到３０ｄＢ，附加损耗为０．２３ｄＢ。     

复合型变耦合系数定向耦合器开关特性的研究

研究了高斯—常数—高斯平滑连接的复合型变耦合系数定向耦合器的开关特性曲线。研究了耦合器各分段长度对开关曲线的影响。数值模拟发现,耦合器各组成部分的参量对耦合器开关曲线尾部的振荡及开关功率的大小均有影响,且呈现出一定的规律性。高斯型波导部分的相对长度以及直波导部分所占份额共同决定了耦合器开关曲线尾部的振荡大小,且开关曲线的振荡与耦合函数的傅里叶变换的振荡密切相关。     

可调抛光型光纤耦合器对位公差的分析

本文导出可调抛光型光纤耦合器在上、下石英基块出现纵向或横向位移及立体交角时的耦合功率公式,从而给出各种可调抛光型光纤耦合器的对位公差和设计依据.     

三芯非线性光纤耦合器中的短脉冲光开关

利用变分法研究三芯非线性光纤耦合器中的短脉冲光开关,解析分析线性三耦合非线性Schr?dinger方程的结果与数值模拟符合得很好.并且得到在非线性光纤耦合器中孤子的耦合长度和开关阈值,与连续波情况和两芯光纤耦合器的结果不同. 关键词： 光纤耦合器 光开关 耦合长度 开关阈值     

具有高阶耦合色散系数三芯光纤耦合器非线性光开关特性的研究

利用两种方法研究了高速光脉冲在具有交叉相位调制的等边三角形排列结构的非线性三芯光纤耦合器中传输和开关特性.首先利用变分原理得到三纤芯中传输转移系数随距离变化的方程,然后利用分裂步长傅里叶方法求得了光脉冲的数值解.变分法和数值模拟的结果表明：当一阶模间色散系数较小时,光脉冲仍能在三芯之间周期性耦合传输,并且表现出良好的开关特性,但是随着一阶模间色散系数的增大,脉冲耦合传输的周期性和陡峭的开关特性都遭到破坏,光脉冲在传输中发生分裂;二阶耦合色散系数和初始啁啾都能使光脉冲传输时的耦合长度变短、光脉冲在三纤芯之间 关键词： 三芯光纤耦合器 模间色散系数 耦合长度 开关阈值功率     

基于非对称三芯光子晶体光纤的宽带定向耦合器研究

提出了一种基于三芯光子晶体光纤的定向耦合器。通过增大纤芯两侧空气孔直径来引入非对称纤芯,该方法有效地实现了1×3分束的目的。数值分析表明,该三芯光子晶体光纤定向耦合器的工作带宽可达113.9nm(具体为波长从1530.9～1644.8nm)且均匀性小于0.4dB、偏振相关损耗低于0.2dB。此外,这种结构能够有较大的制作容差,具体表现为器件长度在光纤长度(20.9mm)的±4%范围内变化都能保证工作带宽不小于80nm。     

拉曼增益对孤子传输特性的影响

利用考虑拉曼增益效应的非线性薛定谔方程, 在忽略光纤损耗的情况下, 采用基于MATLAB的分步傅里叶数值算法, 得出线性算符和非线性算符具体的表达式, 分步作用于光孤子脉冲传输方程, 仿真模拟了光孤子在光纤中传输时的演变. 与不考虑拉曼增益的光孤子在光纤中传输相对比, 探析了拉曼增益对孤子传输特性的影响.拉曼增益会破坏孤子的传输周期, 导致孤子在光纤中传输时快速衰减, 并且影响程度和输入孤子的脉冲峰值功率大小有关, 拉曼增益对基态孤子和高阶孤子的影响也不相同. 关键词： 拉曼增益 孤子 对称分步傅里叶法 非线性薛定谔方程     

多芯光纤对角芯反射耦合器

提出一种多芯光纤对角芯反射耦合器,可实现多芯光纤对称纤芯的光路低损耗串联。首先,采用纤端精密研磨的方法制备出45°圆台,得到平均插入损耗为2.14 dB的器件;其次,通过研磨制备出多角度圆台,并采用电弧平滑优化的方法实现了圆台的弧形优化,使得平均插入损耗降低至1.39 dB。对2种圆台型器件的制备容差进行了对比分析,结果表明,优化后的弧形圆台相较于优化前具有更好的制备容差和性能。     

超高斯型光脉冲在零色散区传输特性的研究

根据超短脉冲在光纤中传输所遵从的高阶非线性薛定谔方程,采用分步傅里叶方法模拟了超高斯型超短脉冲在光纤中的传输演化.在零色散区对损耗、高阶色散、高阶非线性、啁啾等因素对光脉冲传输的影响进行分析并得出了一些结论:损耗对传输脉冲的形状影响比较小基本上可以忽略,对脉冲的幅度影响比较大.一阶孤子传输一段距离后稳定时的幅度和脉宽在传输时基本不变,是进行光孤子通信的理想载体,而高阶孤子在开始传输和传输过程中的幅度和脉宽变化较大.当这些因素共同作用时,对脉冲的传输特性有较大的影响.但通过合理的选择各个影响因素的参量,能得到一个比较适于信息传输的高阶孤子脉冲.这对通过提高入射光脉冲功率使光脉冲在光纤中形成高阶孤子来提高两光中继器之间的中继距离的研究有一定的参考意义.     

磁光光纤中光脉冲的非线性传播特性研究

根据光纤中磁光效应与非线性效应的微扰理论,推导了磁光光纤中光脉冲的非线性耦合模方程,比较了修正的分步傅里叶算法中磁光效应的时域和频域处理方案,表明了在步长足够小的情况下,两种方案的结果一致.分析了磁光效应、光纤非线性以及色散对光脉冲传输特性的影响,通过改变磁光耦合强度,不但可以灵活控制脉冲形状,还可以改变非线性引起的频率啁啾大小,有助于实现基于光脉冲展宽的动态整形功能.本文给出的理论分析方法,有助于开发可用于光纤通信、光纤传感等领域的基于非线性磁光光纤的新型磁光信息处理器件.     

Phase-induced switching in fiber nonlinear directional coupler

A numerical study of soliton switching characteristics and the maximum output coupling by the relative phase change of a control pulse is carried out for input powers, coupled coefficient and input soliton width. It is shown that input powers ratio, coupled coefficient and input soliton width play important roles in this mode of soliton switching and that these effects may lead to useful soliton switching if the relative phase of the control pulse is monitored judiciously.     

Soliton switching and propagation in two-core nonlinear fiber coupler with high order coupling coefficient

We use the variational approach (VA) and the split-step Fourier transforms (SSFT) to study the transmission and switching characteristics inside the fiber nonlinear directional coupler (NDLC). The results, based on the VA, indicate that the second-order coupling coefficient dispersion and initiative chirp all reduce the coupling length, and the second-order coupling coefficient dispersion makes the switching characteristics become sharper and threshold power become bigger under the case of not having initiative chirp. The outcomes, based on the SSFT, indicate that the first order intermodal dispersion coefficient make optical pulses splitting in the propagation of fundamental solitons, and the second-order coupling coefficient dispersion reduces the coupling length, sharpens the switching characteristics and increases the switching threshold power, the results agrees well with those from the VA.     

Vector soliton switching in a fiber nonlinear directional coupler

This paper reports a detailed numerical study of soliton switching in a high as well as low birefringent nonlinear coupler. It is shown that by controlling the polarization angle one can have nearly 100% transmission with excellent switching characteristics. It is shown that soliton remains stable during its propagation inside the coupler. However it is observed that high birefringent coupler exhibits relatively better soliton stability. We show that the coupler could be used as a soliton switch even at an input peak power less than the critical power, the power at which 50-50 power sharing takes place between the two cores, just by a judicious choice of the polarization angle.     

Measurement of fiber propagation constants using a prism-fiber coupler

We report on the use of a prism-fiber coupler to determine the propagation constants for the scalar modes in an optical fiber by measuring, respectively, the incident angle, θ_i, and the position of the m-lines coupled out of the fiber by the prism coupler. The position is related to the value of the corresponding propagation constant. The degeneracy of the modes is shown on the m-line photographs. Good agreement is obtained between measured and calculated values of the propagation constants.     

All-optical amplification via the interaction among guided and leaky propagation modes in lithium niobate waveguides exploiting the cascaded second-order nonlinearity

The aim of this paper consists of performing a theoretical investigation of an all-optical amplifier and discussing the problems for a realistic implementation. An original periodically poled lithium niobate channel waveguide, having the optical c-axis opportunely oriented on the xz plane was considered. The waveguiding structure, designed to operate in the second communication window of optical fibers, shows versatile properties as was theoretically demonstrated. In fact, it enables both the selection and the coupling strength of four different propagation modes, two guided and two leaky, interacting via the cascaded second-order nonlinearity. The coupling among guided and leaky modes is obtained by means of two different techniques: (i) birefringence phase-matching (BPM) via a suitable orientation of the optical c-axis crystal on the xz plane and (ii) quasi-phase-matching by periodical inversion of the lithium niobate ferroelectric domains. A strong diffusion of magnesium in the region external to the periodically poled waveguiding channel is needed in order to achieve the suitable BPM and to maximize the bounding of the electromagnetic field and, thus, the overlapping integrals. Finally, a powerful refinement of device operation via the use of the seeded second harmonic waves is proposed. Gains of the order of 20 dB are achieved with reduced bias powers. The order of magnitude of the bias power decreases, with respect to the unseeded second harmonic operation, from 145 to 32 W.     

基于高非线性光纤中非线性偏振旋转效应的全光逻辑门研究

提出了一种新型的基于高非线性光纤(HNLF)中非线性 偏振旋转(NPR)效应的全光逻辑门实现方案. 将两路非归零码数据信号A和B以及一路直流光同时注入HNLF, 光功率变化导致的非线性双折射在两个偏振分量上引入非线性相对相移, 从而导致光信号的偏振态旋转. 在HNLF输出端, 通过波分解复用器和偏振分束器同时滤出数据信号和直流光的正交偏振态, 从而同时实现多种基础组合逻辑, 并可以在同一段HNLF中实现较为复杂的半加器、半减器逻辑功能. 理论分析了信号光在HNLF中的偏振态演化, 以及利用HNLF中的NPR效应同时实现多种全光逻辑门的原理. 并在实验中得到了10 Gbit/s全光信号"与”、"非”、"或”、"同或”、"异或”、"A· B”、"A·B”、半加器、半减器等逻辑功能, 验证了方案的可行性.     

A comparative study of soliton switching in a two- and three-core coupler with TOD and IMD

A numerical study of soliton switching in a two- and three-core coupler is carried out taking into account the effect of intermodal dispersion and third-order dispersion. A two and three-core coupler with linear and triangular configuration is considered. It is found that the three-core coupler with linear configuration shows the best switching characteristics.     

单模光纤中三阶色散对超短光脉冲传输的影响

基于超短光脉冲在单模光纤中传输时高阶非线性效应的影响。应用非线性薛定谔方程(HONLS)理论,考虑光纤色散三阶效应,推导出无啁啾的高斯脉冲沿光纤传输时脉冲变化的表达式,并对理论结果进行了数值模拟与分析。结果表明,三阶色散会引起光脉冲形状发生畸变,会在其前沿或后沿附近形成非对称的振荡结构。     

八角光子晶体光纤传输特性与非线性特性研究

基于有限元法对一种全内反射型八角光子晶体光纤的传输特性和非线性特性进行了研究,并改变该光子晶体光纤空气孔结构参数得出了其特性与光波长的曲线关系图. 最终得到一种新结构光子晶体光纤,在入射光波长为1.55 μm低损耗窗口处具有非常优越的传输特性和较平坦非线性特性. 关键词： 光子晶体光纤 色散 损耗 非线性系数