非自治拉曼多色孤子的管理和传输

以变系数的非自治非线性薛定谔方程为模型,考虑了一种色散、非线性和自发拉曼散射效应管理下的非自治系统,通过简单变换显式给出了该系统的精确非自治拉曼多色孤子解。基于精确孤子解,解析研究了该拉曼多色孤子在非自治管理系统中的演化特性,发现孤子的中心位置、波数与色散和非线性以及拉曼效应有关,而孤子频移仅与拉曼效应的参数决定,拉曼效应主导了非自治孤子的自频移,引起了孤子的频移在传输过程中不断的发生变化,导致了孤子的多色性。另外,我们数值讨论了该非自治孤子的传输稳定性,结果表明:该非自治拉曼多色孤子在有限的扰动下具有较好的稳定性。     

具有周期非均匀扰动的色散管理系统中的孤子传输

在准理想的色散管理系统中建立了非均匀扰动模型,研究了它们对孤子传输和相互作用的影响.这些扰动导致孤子崩塌,加剧了孤子间相互作用.它们影响的大小与周期长度和扰动强度有关,并且存在最坏周期长度和扰动共振现像.最后,引入非线性增益和滤波器来有效控制这些扰动的影响.     

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.     

具有随机色散的光时分复用系统中色散管理孤子相互作用

本文采用变分法和数值方法研究了具有随机色散的光时分复用系统中色散管理孤子相互作用.发现随机色散增强了孤子间相互作用, 产生了导致孤子淹没的振幅和间隔涨落.相互作用距离与初始间隔、初始相对相位、脉宽和初始相对振幅有关.     

自散焦非局域非线性材料中的光学涡旋孤子

通过数值模拟的方法对非局域非线性自散焦材料中的光学 涡旋孤子的传输特性以及相互作用特性进行了研究. 研究表明, 拓扑荷|m|=1的非局域涡旋孤子是稳定的, 而拓扑荷|m|>1的非局域涡旋孤子均具有拓扑不稳定性. 在微扰存在的情况下以及在近距离相互作用的过程中, |m|>1的涡旋孤子会分裂成一系列的|m|=1的涡旋孤子. 非局域涡旋孤子与局域涡旋孤子具有相同的长距离相互作用模式, 即点涡旋相互作用模式. 但两者的短距离相互作用存在一些差别, 在相同的距离下, 两涡旋间的相互绕转的周期随着材料的非局域响应长度增大而增大. 关键词： 非局域非线性薛定谔方程 自散焦 涡旋孤子     

热非局域非线性高阶界面孤子的多种孤子解

讨论了是光束在(1+1)维的热致非局域介质中的传输, 此介质在中心处被分为两部分, 两部分的线性折射率是不同的. 发现在中心处的界面附近存在多阶稳定的界面孤子. 本文研究的是五阶和六阶界面孤子, 它们都存在三种不同的孤子解. 三种孤子解的波形、束宽、光束重心、存在和稳定区间都是不相同的. 五阶孤子的三种解都存在稳定区间, 并且其中两个解存在共同稳定区域. 然而六阶孤子只有其中一种解存在稳定区间.     

差分相移键控色散管理孤子多扰动系统的相位抖动

差分相移键控(DPSK)调制方式和色散管理孤子传输方式的结合能抵制噪声和非线性损伤,在高速(40 Gbit/s以上)多信道系统中具有突出的优点。采用变分法分析了多波长信道的放大自发辐射(ASE)噪声、信号间的非线性串扰(ISI)等多种扰动因素引起差分相移键控色散管理孤子系统的均方根相位抖动,给出了扰动的作用区域以及各扰动的大小。研究发现,放大自发辐射引起的抖动与传输距离成三次方的关系,而交叉相位调制(XPM)引起的抖动与距离近似成线性关系。通过优化选择色散管理图强度范围1.5~3.5,各种扰动得到了抑制,而以放大自发辐射扰动抑制为最大,此时要远低于交叉相位调制引起的抖动,然后分别是交叉相位调制-放大自发辐射扰动和交叉相位调制,从而波分复用系统主要来自于增加信道数这一客观限制。     

双折射光纤中色散管理孤子研究

研究色散管理孤子在双折射光纤中的传输特性.应用变分法分析并给出了双折射光纤中色散管理孤子参量演化的常微分方程.数值分析双折射对孤子参量的影响,分析发现在双折射光纤中色散管理孤子的宽度和啁啾不再是严格周期性变化.在色散管理的同时进行周期性偏振补偿可以消除走离效应,可以产生管理孤子.     

非局域非线性耦合器中暗孤子的传输

研究了空间暗孤子在非局域非线性耦合器中的新解和传输稳定性.发现非局域非线性耦合器中存在稳定的基态暗孤子和多极暗孤子的束缚态.分析了非局域程度、非线性参数、传播常数和耦合系数变化对基态暗孤子的峰值、束宽和功率的影响.讨论了基态暗孤子和多极暗孤子的传输稳定性,发现基态暗孤子在其存在的区域总是稳定的,偶极以及多极暗孤子存在不稳定区间,稳定区间取决于传播常数和介质的非局域程度,并且多极暗孤子的稳定传输还受孤子间距的影响.     

基于系统非线性的红外焦平面非均匀性校正

采用系统非线性描述和分析方法,从基于红外参考辐射源的校正算法原理入手,提出了一种新的红外焦平面非均匀性校正方法.该算法将每个探测器单元视为一个非线性系统,因此,该算法原理既对基于红外参考辐射源的非均匀性校正算法成立,对基于场景的校正算法在一定条件下也有效,能够适应非均匀性随时间和环境改变而发生缓慢变化的情形,是一种自适应算法.     

Dynamics of Nonautonomous Dark Solitons

We solve a generalized nonautonomous nonlinear Schrdinger equation analytically by performing the Hirota's bilinearization method. The precise expression of a parameter , which provides a compatibility condition and dark soliton management, is obtained. Comparing with nonautonomous bright soliton, we find that the gain parameter affects both the background and the valley of dark soliton (∈2≠1) while it has no effects on the wave central position.Moreover, the precise expressions of a nonautonomous black soliton's (∈2≠1) width, background and the trajectory of its wave central, which describe the dynamic behavior of soliton's evolution, are investigated analytically. Finally, the stability of the dark soliton solution is demonstrated numerically. It is shown that the main characteristic of the dark solitons keeps unchanged under a slight perturbation in the compatibility condition.     

Nonautonomous Solitons in the(3+1)-Dimensional Inhomogeneous Cubic-Quintic Nonlinear Medium

We have constructed explicit nonautonomous soliton solutions of the generalized nonlinear Schrdinger equation in the(3+1)-dimensional inhomogeneous cubic-quintic nonlinear medium.The gain parameter has no effects on the motion of the soliton's phase or their velocities,and it affects just the evolution of their peaks.As two examples,we discuss the propagation of nonautonomous solitons in the periodic distributed amplification system and the exponential dispersion decreasing system.Results show that the presence of the chirp not only makes the intensity of solitons weaken more promptly,but also broadens their width.     

Nonautonomous Dark Solitons and Rogue Waves in a Graded-Index Grating Waveguide

We analytically present a family of nonautonomous dark solitons and rogue waves in a planar graded-index grating waveguide with an additional long-period grating.The dark solitons whose dynamics described by the explicit expressions such as the valley,background and wave central position are investigated.We find that dark soliton's depth and the long-period grating have effects on soliton's wave central position;the gain or loss term affects directly both the background and valley of the soliton.For rogue waves,it is reported that one can modulate the distribution of the light intensity by adjusting the parameters of the long-period grating.Additionally,more rogue waves with different evolution behaviors in this special waveguide are demonstrated clearly.     

Double Wronskian Solutions for a Generalized Nonautonomous Nonlinear Equation in a Nonlinear Inhomogeneous Fiber

A generalized nonautonomous nonlinear equation, which describes the ultrashort optical pulse propagating in a nonlinear inhomogeneous fiber, is investigated. N-soliton solutions for such an equation are constructed and verified with the Wronskian technique. Collisions among the three solitons are discussed and illustrated, and effects of the coefficients σ₁(x, t), σ₂(x, t), σ₃(x, t) and v(x, t) on the collisions are graphically analyzed, where σ₁(x, t), σ₂(x, t), σ₃(x, t) and v(x, t) are the first-, second-, third-order dispersion parameters and an inhomogeneous parameter related to the phase modulation and gain(loss), respectively. The head-on collisions among the three solitons are observed, where the collisions are elastc. When σ₁(x, t) is chosen as the function of x, amplitudes of the solitons do not alter, but the speed of one of the solitons changes. σ₂(x, t) is found to affect the amplitudes and speeds of the two of the solitons. It reveals that the collision features of the solitons alter with σ₃(x, t)=-1.8x. Additionally, traveling directions of the three solitons are observed to be parallel when we change the value of v(x, t).     

Transport of Nonautonomous Solitons in Two‐Dimensional Disordered Media

Transport of localized nonlinear excitations in disordered media is an interesting and important topic in modern physics. Investigated in this work is transport of two‐dimensional (2D) solitons for a nonlinear Schrödinger equation with inhomogeneous nonlocality and disorder. We use the variational method to show that, the shape (size) of solitons can be manipulated through adjusting the nonlocality, which, in turn, affects the soliton mobility. Direct numerical simulations reveal that the influence of disorder on the soliton transport accords with our analysis by the variational method. Besides, we have demonstrated an anisotropic transport of the 2D nonautonomous solitons as well. Our study is expected to shed light on modulating solitons through material properties for specifying their transport in disordered media.     

Self—Steepening and Thired—Order Dispersion Induced Optical Solitons in Fiber

Usually,one considers only the group velocity dispersion(GVD)-and self-phase modulation(SPM)-induced solitons in optic soliton communication while other higher order effects such as the third-order dispersion(TOD),self-steepening(SS),and stimulated Raman scattering are considered only perturbatively,In this paper,we study the existence of the TOD-and SS-induced soliton solutions.The existence conditions of the TOD-and SS-induced bright and dark solitons are quite different from those of the GVD-and SPM-induced solitons.     

Optical Solitons with Time-Dependent Dispersion, Nonlinearity and Attenuation in a Kerr-Law Media

This paper obtains the 1-soliton solution of the nonlinear Schr?dinger’s equation with Kerr law nonlinearity and time-dependent dispersion, nonlinearity and attenuation. The solitary wave ansatze is used to obtain this solution. The constraint relation between these time-dependent coefficients is also obtained for the solitons to exist. The variation of the soliton velocity also falls out by this method.     

色散补偿光纤通信系统中孤子之间的相互作用

采用变分原理与位力定理研究了非线性光通信系统色散补偿方案中,相邻孤子之间的相互作用对孤子传输特性的影响。结果表明:在相位匹配与等幅孤子注入时,在普通单模光纤中这两个孤子先相互吸引,而后又相互排斥,显现周期性碰撞的变化规律,形成束缚孤子态,而在色散补偿光纤中传输的孤子之间不发生碰撞;对相位不匹配与等幅孤子注入,孤子之间发生分离;对相位匹配和不等幅孤子注入,在色散补偿光纤中传输的孤子,如果初始间隔φ0越小,应注入较大的初始幅值差η0,以利于孤子的传输。     

Dispersion-Managed Optical Solitons with Higher-Order Nonlinearity

In this paper we have investigated the propagation characteristics of optical solitons in dispersion managed optical communication systems taking into account of the effect of quintic nonlinearity. Using variational formalism, several ordinary differential equations have been established for pulse parameters. These equations have been solved numerically to investigate the propagation characteristics. It has been noticed that stable periodic pulse propagation is possible over long distance. Numerical simulation has been undertaken to show that parabolic nonlinearity reduces collision distance between neighbouring pulses of the same channel.