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.     

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.     

All-optical switching of solitons in an active nonlinear directional coupler

A numerical study of the all-optical switching properties of an active nonlinear directional coupler is presented. The switching power is reduced for both CW and soliton inputs because of the gain. The switching properties of the coupler are enhanced for solitons, which switch nearly completely. For ultrashort pulses, the effects of the bandwidth of the gain medium are considered by using a general form for the gain band. The gain spectrum of erbium is also considered as a specific example.     

Optical solitons switching in asymmetric dual-core nonlinear fiber couplers

With study on the switching characteristics in a asymmetric dual-core nonlinear fiber coupler, it is found the switch efficiencies when the dispersion values of two fibers have opposite signs are much higher than those when they have same signs. Meanwhile, when the dispersion values of two fibers have same signs, the switch efficiencies become much higher if the dispersion value of one core is decreased. In addition, the switch threshold power becomes lower than the one with the same sign if the nonlinearity coefficient of two fibers is opposite. The result shows that asymmetric coupler has much higher switch efficiencies and lower switch threshold power than symmetric coupler.     

Simulation of soliton propagation in a directional coupler

Soliton propagation in a directional fiber coupler is investigated. By using Fourier series analysis technique (FSAT), the effects of radii ratio and intermodal dispersion on soliton switching have been investigated.     

Study of ultra-fast optical pulse propagation in a nonlinear directional coupler

We showed that the application of a soliton in a nonlinear coupler does not show a better switching performance than a Gaussian pulse, unlike what the existing theory expected. Like the Gaussian pulse, a soliton could also suffer distortion, broadening, or narrowing in a nonlinear directional coupler. In addition, by using a new normalized format the linearly coupled nonlinear Schrödinger equations were investigated. For the first time, we found that both the coupling behavior and the switching performance of pulses in a nonlinear coupler depend on the product of the coupling coefficient and the dispersion length. We also showed that for a given nonlinear coupler with a Gaussian-like or soliton-like pulse input, switching performance and whether a pulse breaks up or not mainly depend on the input pulse width, not the pulse shape. PACS 42.65.Tg; 42.65.Wi; 42.81.Qb     

Soliton Properties of Light Pulses on the Surface of Ionic Crystals Generated by Strong Nonlinear Effects

In this paper, we theoretically discuss the soliton properties of light pulse transportation on the surface of an ionic crystal having strong nonlinear interactions between ions of unit cells. We analyze in detail the dark solitons when the nonlinear coefficient g is positive and negative, respectively. It is found that whether the nonlinear coefficient g is positive or negative, the dark solitons can be formed over the whole dispersion relation area of surface polaritons considering nonlinear effects. Attention should be paid to the fact that around ωTO, the light pulse can form advanced dark solitons, and there is a switching area from advanced dark soliton to retarded dark soliton near ωTO. We also discuss the effects of higher nonlinear dispersion on the solitons.     

Effect of dark soliton on the spectral evolution of bright soliton in a silicon-on-insulator waveguide

The spectral evolution of bright soliton in a silicon-on-insulator optical waveguide is numerically simulated using the split-step Fourier method. The power and input chirp of the dark soliton and the second-order dispersion are varied to investigate the effect of dark soliton on the spectrum of bright soliton. The simulations prove that the dark soliton modifies the spectral shape of the bright soliton. Further, the variation in the power of dark soliton affects the splitting of bright soliton. Furthermore, the chirped dark soliton can improve the spectral width and flatness. The variation in the dispersion of dark soliton modifies the phase matching of the bright soliton and the dispersive wave emission, thereby affecting the spectral evolution.     

Zeno effect and switching of solitons in nonlinear couplers

The Zeno effect is investigated for soliton type pulses in a nonlinear directional coupler with dissipation. The effect consists in increase of the coupler transparency with increase of the dissipative losses in one of the arms. It is shown that localized dissipation can lead to switching of solitons between the arms. Power losses accompanying the switching can be fully compensated by using a combination of dissipative and active (in particular, parity-time-symmetric) segments.     

超常介质中暗孤子的形成和传输特性研究

利用一种扩展的双曲函数级数方法求解超常介质中的传输方程，得到了各种不同情形下的暗孤子解，分析了可控自陡效应和二阶非线性色散效应对孤子形成和传输特性的影响.结果表明，超常介质中负的自陡效应使得暗孤子的中心位置随传输距离向脉冲前沿方向漂移，与常规介质中自陡效应(恒为正)的作用相反；特别是，由于二阶非线性色散的作用，使得在没有线性群速度色散的情形下同样可形成孤子，而且在反常线性色散情形也可形成暗孤子.     

Optical <Emphasis Type="Italic">Gaussons</Emphasis> and dark solitons in directional couplers with spatiotemporal dispersion

This paper study the dynamics of optical solitons for nonlinear directional couplers. This coupler system is considered with the group velocity dispersion and the cross-phase modulation of two components along with the spatiotemporal dispersion coefficients. The constraint conditions for the existence of optical Gaussons and dark solitons are listed under the log law and Kerr law nonlinearities, repectively. Additionally, a couple of other solutions known as singular periodic and combined dark-singular solitons, fall out as a by-product of this scheme. This scheme however fails to retrieve bright soliton solution.     

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     

A comparative numerical study of soliton switching in a nonlinear directional coupler with saturating nonlinearity

A detailed numerical study of soliton switching in a nonlinear directional coupler with saturating nonlinearity is carried out. All commonly used models have been studied. Relevant physical characteristics for switching have been determined, compared and discussed.     

A variational analysis of soliton switching in an NLDC with saturating non-linearity

A comparative analysis of soliton switching in a non-linear directional coupler with saturating non-linearity is carried out by a variational method. Two models of fractional non-linearity, one the usual unaveraged and the other obtained after averaging over the fibre cross-section, are considered. It is shown that the switching characteristics differ (for the same set of fibre parameters), qualitatively as well as quantitatively, for these models. The soliton switching characteristics in both the models are obtained, compared and discussed.     

一种基于非线性光纤环镜开关特性的超短光孤子产生方法

提出了一种利用非线性光纤环镜的开关特性将连续波同时转化为亮孤子和暗孤子的新方法 ,即让连续波和另一波长的调制脉冲串共同耦合入光纤环镜 ,交叉相位调制使得一部分连续波被环镜透射 ,其余部分被反射 ;再让透射波和反射波分别在反常色散光纤和正常色散光纤中传输 ,自相位调制和群速度色散之间的相互作用使得透射波和反射波分别演化为亮、暗孤子。数值计算表明 ,该方法不仅可产生脉宽比调制脉冲窄、重复频率比调制脉冲高的亮孤子和暗孤子 ,而且几乎可将全部的连续波能量转化为孤子能量。     

Soliton switching study using new normalized nonlinear Schrödinger equations

Soliton switching in a nonlinear directional coupler (NLDC) is studied by using new normalized nonlinear Schrödinger equations (NLSE). The resulted equations have one parameter κL_D only, this feature greatly simplifies the numerical study of soliton coupling in a NLDC, and it enables us to derive the soliton switching conditions based on numerical analysis. Numerical results show that most of the input soliton energy remains in the launched waveguide when input soliton normalized peak power is bigger than 2.5. It is contrary to the existing theoretical expectations which were derived using variational approach. The fundamental soliton switching conditions is also expressed in terms of input soliton pulse width. In addition, it is found that frequency chirp degrades soliton switching performance in a NLDC.     

SOI无间距定向耦合光开关模型分析及设计

提出了一种简便可行的ＳＯＩ无间距定向耦合光开关（ＢＯＡ型－Ｂｉｆｕｒｃａｔｉｏｎ Ｏｐｔｉｑｕｅ Ａｃｔｉｖｅ）模型分析方法，采用等离子体色散效应这种光开关的电学调制机理；而用ｐｎ结大注入效应分析开拳电学性质；并根据大截面单模ＳＯＩ脊形波导理论和上棕分析，设计了利用双模干淑机制工作的这种器件的结构参数和电学参数。     

非均匀光纤中暗孤子传输特性研究

由于变系数非线性Schrödinger方程的增益、色散和非线性项都是变化的, 根据方程这一特点可以研究光脉冲在非均匀光纤中的传输特性. 本文利用Hirota方法, 得到非线性Schrödinger方程的解析暗孤子解. 然后根据暗孤子解对暗孤子的传输特性进行讨论, 并且分析各个物理参量对暗孤子传输的影响. 经研究发现, 通过调节光纤的损耗、色散和非线性效应都能有效的控制暗孤子的传输, 从而提高非均匀光纤中的光脉冲传输质量. 此外, 本文还得到了所求解方程的解析双暗孤子解, 最后对两个暗孤子相互作用进行了探讨. 本文得到的结论有利于研究非均匀光纤中的孤子控制技术.     

The effect of relative phase on the stability of temporal dark soliton in $${{\mathcal {}}}$$-symmetric nonlinear directional fiber coupler

In this paper, we numerically investigate the effect of relative phase on the stability of dark solitons in \({\mathcal {PT}}\)-Symmetric nonlinear directional coupler (NLDC), by considering gain in the bar and loss in the cross in the range of \(\theta =0^\circ\) to \(180^\circ\). The \({\mathcal {PT}}\)-Symmetric perturbed eigenfunctions are used to study the soliton stability. The results of simulations are shown that in the first half region of the relative phase the soliton is unstable while in the second one, is stable. In the stable region gain and loss cancel each other and also the perturbed eigenfunctions have no effect on solitons while in the unstable region solitons are amplified in the bar and attenuated in the cross except for some small intervals which the roles are changed. The behavior of such perturbation can be interpreted as self all-optical phase soliton switching and optical logic gates.     

Ge_xSi_（1－x）／Si异质结无间距定向耦合光开关模型分析

提出一种简便可行的ＧｅｘＳｉ１－ｘ异质结无间距定向耦合光开关（ＢＯＡ型－ＢｉｆｕｒｃａｔｉｏｎＯｐｔｉｃａｌＡｃｔｉｖｅ）模型分析方法。该方法采用等离子体包散效应分析了这种光开关的电学调制机理；采用异质结超注原理分析了开关的电学性质；并根据典单模脊形波导理论和上述分析，设计了利用双模干涉机制工作的Ｇｅ０．０５ＳＩ０．９５／Ｓｉ异质结ＢＯＡ型光开关的结构参数和电学参数。