光学孤子在单模光纤中的非线性传输方程

人们熟知,由非线性薛定谔(NLS)方程描述的光学孤子可以在单模光纤中稳定地传输。本文在准单色近似和慢变包络近似条件下,利拥泰勒级数展开推出了这一非线性传输方程。由于推出的方程包含着高阶线性色散和光纤损耗项,因而可以用来研究短光脉冲(皮秒量级)在单模光纤传输过程中相关的非线性光学孤子效应,比如光学孤子分裂和光学孤子损耗等。     

光孤子高阶色散部分的函数级数近似

本文用函数级数法导出合高阶色散的非线性薛定谔方程的解析近似解；研究了高阶色散对光孤子传输的影响。分析与研究表明，近似解中高阶项对传输影响很小，可略去不计．     

高非线性光子晶体光纤中飞秒脉冲压缩(特邀)

采用全矢量有限元法和分步傅里叶法模拟计算了高非线性光子晶体光纤在近红外光谱区（特别是在850 nm）的飞秒脉冲孤子效应压缩,提出了一种新的反常群速度色散（2=-50.698 ps2/km）、小高阶色散和高非线性（=268.419 1 W-1/km）二氧化硅芯光子晶体光纤结构,建立了包含高阶色散和拉曼散射的非线性薛定谔方程,研究了高斯脉冲在此光纤中传输时,光纤长度和孤子阶数对脉冲压缩的影响,分析了光纤中2~5阶色散,研究表明:孤子阶数为8时,品质因子和压缩因子均达到最大,初始脉冲的峰值功率P0=3 357.8 W,压缩效果最好;优化光纤几何和光学参数,可以得到了高品质因数、小底座的超短光脉冲。     

高阶色散效应对孤子和孤子对传输的影响

用数值法求解含高阶色散效应的光孤子NLS方程,数值求解发现三阶色散效应使孤子脉座单边振荡和四阶色散效应使孤子脉座的双边振荡,导致临近的脉冲相互重叠和脉冲形状畸变,在孤子对间激起次脉冲,从而造成系统误码,提出重点应对三阶色散进行补偿以减小系统误码。     

修正高阶非线性薛定谔方程的显式行波解

利用扩展的双曲正切函数法,并借助于符号计算软件Map le,研究了考虑自陡峭效应、 自频移效应后的修正高阶非线性薛定谔方程,获得了多组显示精确行波解,主要包括亮孤子解、暗孤子解和一种新形式的复合孤子解。讨论了这3种飞秒孤子解存在的参量条件,并指出了飞秒亮孤子解存在于负三阶色散区域,而飞秒暗孤子解则存在于正三阶色散区域。     

利用色散缓变管理孤子消除孤子分裂与变形的方法

提出了色散缓变管理孤子概念，研究了孤子在该系统中的传输特性。结果表明，色散缓变光纤使孤子脉宽变短效应能有效地抵消孤子脉冲的展宽，只要恰当选择色散强度值，就能获得脉宽、峰值功率和波形都很稳定的孤子传输。     

A novel approach to solving the nonlinear Schrodinger equation bythe coupled amplitude-phase formulation

A novel approach for solving the nonlinear Schrodinger equation (NLSE) analytically is presented in this paper. Fundamental soliton solutions have been obtained for both anomalous dispersion regimes (β₂<0) and normal dispersion regimes (β₂ >0) without using inverse scattering or the Backlund transform. By considering the amplitude and the phase of the complex solution separately, a set of amplitude-phase coupled nonlinear equations is derived from the NLSE. The characteristic equation satisfied by the envelope amplitude is obtained for the fundamental soliton and soliton-modulated wave. The conditions to be satisfied by the phase propagation constant and soliton power give rise to useful criteria for the design of optical soliton communication systems. Numerical simulations agree well with theoretical results     

Nonlinear dynamics of femtosecond optical solitary wave propagationat the zero dispersion point

A perturbed nonlinear Schrodinger equation, describing nonlinear pulse propagation of femtosecond duration in optical fibers at the zero dispersion point, is considered. This equation is reduced to an ordinary differential equation, which is treated by means of Hamiltonian dynamics techniques. Conditions for solitary wave formation, as well as the solutions themselves, namely, a bright soliton, a rarefaction soliton, and a pair of dark solitons, are derived analytically. The shifts of the solitary wave velocity, the angular frequency, and the wavenumber, as well as the peak power required to launch a bright soliton are also obtained. The connection among the point initial conditions of the pulse and the type of solitary wave that can be excited is finally presented     

光纤中高阶项对光孤子传输的影响

本文从修正的高阶非线性薛定谔方程出发,分别讨论了光纤中高阶项,诸如线性高阶色散效应、非线性高阶色散效应和自感应喇曼效应对光孤子传输的影响,并介绍了这些高阶项对光纤孤子传输综合影响的结果和光纤孤子通信的应用前景。     

Optical Delay Lines Based on Soliton Propagation in Photonic Crystal Coupled Resonator Optical Waveguides

In this paper, a study of optical delay lines based on soliton propagation in coupled resonator optical waveguides is performed. For a given bit rate and required delay, design equations are given that relate the soliton peak power and collision period to the soliton width. To study the influence of higher order linear and nonlinear dispersion, a continuous wave propagation model incorporating these effects is also derived. Using this model, the soliton stability in the presence of higher order dispersion, optical loss and adjacent soliton pulses is numerically verified. It is also shown that soliton-based delay lines can achieve nanosecond delay at a propagation length of a few millimeters due to the high slow down factors that can be obtained.     

非线性光孤子传输方程的研究

本文在从描述光孤子在单模光纤中的非线性传输方程（ＮＬＳ，即非线性薛定谔方程）出发，利用Ｍａｘｗｅｌｌ方程和慢变包络近似性，导出ｐｓ量级光孤子高阶修正的非线性薛定谔方程（ＨＭＮＬＳ）可进一步研究色散，损耗等高价效应对孤子传输造成的影响。     

非线性光孤子传输方程

本文基于麦克斯韦方程和利用太勒级数展开严格地建立了描述光孤子传输的非线性薜定谔方程,可以用来分析损耗、高阶线性色散和高阶非线性色散效应对光孤子传输的影响。     

光纤非线性孤立子通信

在单模光纤异常色散区,当非线性与色散平衡时,初始注入的光脉冲演化形成光孤立子。利用光孤立子可实现无畸变传输,大大提高光纤通信系统的容量和中继距离。本文简述了光孤立子产生的机理,用一种简明通用的方法求得了多种形式的光纤非线性传输方程,给出了无损耗非线性传输方程基态孤立子解完整的一般表示式,同时对孤立子系统设计进行了讨论。     

Polarization mode dispersion, decorrelation, and diffusion inoptical fibers with randomly varying birefringence

Polarization mode dispersion and the polarization decorrelation and diffusion lengths are calculated in fibers with randomly varying birefringence. Two different physical models in which the birefringence orientation varies arbitrarily are studied and are shown to yield nearly identical results. These models are appropriate for communication fibers. We show that both the length scales for polarization mode dispersion and polarization decorrelation measured with respect to the local axes of birefringence are equal to the fiber autocorrelation length. We also show that the coupled nonlinear Schrodinger equation which describes wave evolution over long length along a communication fiber can be reduced to the Manakov equation. The appropriate averaging length for the linear polarization mode dispersion is just the fiber autocorrelation length but the appropriate averaging length for the nonlinear terms is the diffusion length in the azimuthal direction along the Poincare sphere which can be different, The implications for the nonlinear evolution are discussed     

高阶色散和非线性效应下三阶孤子对传输的研究

高阶色散及高阶非线性效应是制约光孤子稳定传输的重要因素。基于光孤子传输的非线性薛定谔方程,综合考虑三阶色散和五阶非线性的影响,采用分步傅里叶算法,数值研究了三阶孤子对间的相互作用。结果表明：三阶色散导致三阶孤子对无规则地裂变,裂变后的光脉冲形状发生畸变,脉冲中心位置出现偏移;考虑负五阶非线性作用后,在一定程度上抑制了孤子裂变,但是光脉冲在传播过程中伴有能量转移。而正五阶非线性作用使三阶孤子对传输图形进一步恶化。适当地选取负五阶非线性参数值,可以完全消除三阶孤子对的裂变和相互作用,改善了脉冲中心位置的线性偏移。     

普通单模光纤中光孤子传输问题的研究

在使用普通单模光纤的光孤子传输系统中,放大器自发辐射（ASE）噪声和色散波逸出是限制光孤子传输的两个主要因素,它们将引起孤子能量科动和定时抖动,从而导致系统误码。本文分别研究了带限光滤波器对ASE噪声的抑制和非线性增益对色散波的抑制以及对孤子传输系统的稳定作用,并设计了使用普通单模光纤的光孤子传输系统。     

高阶色散对光孤子及孤子对传输的影响分析

为了研究高阶色散对光孤子及孤子对传输的影响,采用分步傅里叶变换方法,对含高阶色散效应与不考虑高阶色散情况下的光孤子非线性薛定谔方程进行了数值求解,得到了孤子脉冲形状与色散阶数有着相关性这一结果.结果表明,奇数阶色散效应会使孤子及孤子对脉冲发生单边振荡,产生能量损耗,并在振荡侧产生次脉冲,而偶数阶色散效应会使孤子及孤子对脉冲发生明显的脉宽展宽,高阶色散效应对孤子脉冲的影响随阶数的增加而减弱.     

Elimination of Split and Deformation for Optical Soliton in TIRPCF Using CSDDMS

The concept of the concentrated slowly decreasing dispersion management soliton（CSDDMS） is explained, and the nonlinear Shroedinger equation （NSE） of the soliton propagation in the total internal reflective photonic crystal fiber （TIRPCF） under the multi-photon nonlinear Compton scattering is given. Through solving of this equation using the Fourier transform by step, it is found that under certain conditions, the soliton couple becomes into the quasi-solitons, whose amplitudes and widths are slowly and periodically changed, but there is any collision. A new method to eliminate the split and deformation of the optical soliton in the TIRPCF using the CSDDMS is proposed.     

非线性双折射阶跃光纤中的极化调制不稳定性

利用光脉冲在光纤中传播时所遵守的相干非线性薛定谔耦合方程,研究了线偏振光在 弱双折射阶跃光纤中的传输特性。结果表明,由于线性双折射和色散的相互作用,导致光的偏振态发生变化,产生交叉相位调制(XPM) ,从而导致相位匹配参量的四波混频。这一过程不仅在反常色散区产生,在正常色散区也能产生,并且当表征距离的级数m发生变化时,也随之发生变化。     

Magnetostatic-wave envelope soliton in microstrip line usingYIG-film substrate

In this paper, a dispersion relation of the microstrip line on a yttrium-iron-garnet (YIG)-film substrate has been derived under the approximation of a two-dimensional analysis. The dispersion curve shows the mixed state of quasi-TEM mode and magnetostatic forward volume wave (MSFVW) mode, and these two modes are coupled with each other at gyromagnetic frequency where MSFVW solitons are excited efficiently. Based on the numerical parameters of the calculated dispersion curve, simulation of the soliton form has been carried out by numerically solving the nonlinear Schrodinger equation. The results are compared with the experimental results of MSFVW envelope bright soliton in a microstrip line on YIG-film-gadolinium-gallium-garnet substrate