光折变屏蔽光伏亮孤子相互作用研究

为了得到两个或多个光折变屏蔽光伏亮孤子之间相互作用结果,采用数值方法分析了两个或多个屏蔽光伏亮孤子之间的相互作用。两同相孤子作用时表现为相互吸引,并伴有融合现象,且孤子融合发生时的作用距离随着孤子初始间距的增大而增大;两反向孤子相互排斥,且排斥作用随孤子初始间距的减小而增强;当两孤子的相位差位于区间(0,π)和(-π,0)中时,其相互作用过程中伴有能量的转移,两区间中能量转移方向相反。多个同向孤子相互作用时,不同于两个孤子周期的融合和分开,而是在整体吸引过程中发生孤子的逐步融合作用。当中间孤子与两边孤子的相位差是π/2时,多个孤子之间存在能量转换。而邻近相互反相的多个孤子相互作用时,能保持很好的稳定性传播。结果表明,这种相对相位控制下的两孤子问相互作用的变化有望用于光开关器件。多个孤子作用结果对形成孤子阵列及阵列波导具有指导意义。     

光诱导光学晶格中高斯型孤子的开关行为

讨论了高斯型空间光孤子在光折变介质光学晶格的传输行为,运用分步傅里叶变换法对传输方程进行数值分析.研究表明:单个斜入射高斯型光孤子在周期性光学晶格中会局限于入射波导传输或在合适振幅的情况下穿过若干波导再自陷于某个波导;而当同时存在正入射和斜入射孤子时,两者相遇后会发生反射或透射,并可通过斜入射光孤子的振幅选择反射或透射.     

Light that acts like `natural bits' [solitons]

Solitons, ultrastable light pulses that could revolutionize long-haul, fiber-optic communications and perhaps even optical switching, are discussed. Two classes of solitons are described. Temporal solitons, pulses of light that resist a medium's chromatic dispersion, or tendency to broaden them in time, have been known for a while. They offer the possibility of all-optical communication systems transmitting signals thousands of kilometers. Erbium-doped fiber amplifiers provide an all-optical form of soliton amplification that brings such lightwave systems closer to reality. Spatial solitons, which are actually light beams that travel through a planar waveguide without self-focusing or spreading, were observed for the first time last year and might eventually prove useful for optical switching     

Solitons in optical communications

In this paper we have calculated the effects of loss on the propagation of soliton solutions of the nonlinear Schrodinger equation. Since we are interested in the application of these results to optical communications, it is necessary to go beyond perturbative results. This is due to the fact that propagation distances in optical fibers are significantly greater than the decay length of the energy in the pulses. Some conclusions are drawn about the application of solitons in long-distance communications.     

Detection and estimation of multiplexed soliton signals

Solitons are eigenfunction solutions to certain nonlinear wave equations that arise in a variety of natural and man-made systems. Their rich properties and tractability make them an intriguing component of such systems, often describing the large-scale or long-term behavior of natural systems, or the information content in certain communication or signal processing systems. However, it is often difficult to detect or estimate the parameters of solitons in such systems due to the presence of strong nonsoliton components or the nonlinear interaction of multiple solitons. The objective of this paper is to develop and investigate the detection and estimation of soliton signals. As a framework for this study, we consider using these nonlinear systems as both signal generators and signal processors in a form of multiplexed soliton communication. In contrast to more conventional uses of solitons in a communications context, our communication system uses soliton systems for signal generation and multiplexing for transmission over traditional linear channels. In addition to their mathematical tractability and the simplicity of the analog circuits used to generate and process them, we show that the soliton signal dynamics may also provide a mechanism for decreasing transmitted signal energy while enhancing signal detection and parameter estimation performance     

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     

三阶孤子传输和相互作用的数值研究

用分步富里叶变换法求解三阶孤子传输的NLS方程,得到了在此条件下孤子传输的数值图形,发现三阶孤子在传输中被压缩和裂变,三阶孤子的相互作用加速了孤子的裂变。通过增加二阶色散系数可抑制孤子的裂变和孤子在传输中的相互作用。     

相干泵浦微腔光孤子基础与双光梳应用（特邀）

光学孤子是指一种通过非线性折射率势阱维持脉冲形状不变的光波,它广泛存在于光纤、飞秒激光器、参量振荡器等系统中。近年来,人们在相干泵浦下的高Q值微腔中也观测到了光孤子,这为研究光孤子性质提供了新的实验平台。又因为微腔光孤子在频域上对应高重频的光学频率梳,微腔光孤子的诞生也极大地推动了小型化光学频率梳的发展。微腔光孤子频率梳已经可以实现自参考锁定;这使得片上集成的光频合成器、光原子钟、波分复用光源、微腔光谱仪、微腔激光雷达等众多应用成为了可能。文中介绍了微腔光孤子的产生基础,特别是光孤子相互作用相关的研究,还讨论了基于微腔的双光梳测量在高速成像与中红外气体光谱分析上的应用。     

横向非周期性调制Kerr介质中的空间光孤子

数值方法研究了横向非周期调制Kerr介质中所支持的空间光孤子。数值模拟结果显示研究模型存在三种类型空间光孤子：低功率下的双峰孤子、高功率下的基本孤子和稳定传输的双极孤子。应用线性稳定性分析方法研究了三种类型空间光孤子的稳定传输的稳定谱,总结出三种类型光孤子稳定传输的条件。     

Solitons in communications

Communications of tens of gigabits per second of data over distances of many thousands of kilometres using optical-fibre solitons has been predicted and demonstrated experimentally. This paper reviews the history, physics and engineering of optical-fibre solitons and assesses the problems encountered in realising the concept for high-capacity transatlantic telecommunications. The possibilities of communications inherent in the transmission of pulses which do not suffer dispersion were recognised almost immediately after the mathematical clarification of the soliton, and in 1973 a proposal was initiated by Hasegawa and Tappert for the use of this phenomenon for high-capacity digital communications along optical fibres. The technical issues involved in a proper understanding of this idea are discussed and the impact on technology that has followed the proposal is considered     

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。     

Nonlinear pulse propagation in a monomode dielectric guide

We derive the nonlinear wave equation for an envelope of an electromagnetic wave in a monomode dielectric waveguide. Concrete examples are given for a single-mode optical fiber where the coefficients of resultant nonlinear Schrödinger equation with higher-order dispersion and dissipation (both linear and nonlinear) are given in terms of properties of the eigenfunction of the guided wave as well as of the material nonlinearity and dispersion. Using a newly-developed perturbation method, we show that the higher-order dispersions (linear and nonlinear) perserve the profile of a single soliton but to split up a boundNsoliton (N geq 2) into individual solitons with different heights which propagate at different velocities. We also show that the higher-order nonlinear dissipation due to the induced Raman effect downshifts the carrier frequency of a single soliton in proportion to the distance of propagation and to the fourth power of the soliton amplitude.     

自傅立叶光孤子的相互作用特性

用分步傅立叶变换方法数值求解非线性薛定谔方程,研究了一阶自傅立叶光孤子信号在光纤传输中的相互作用特性。证明了算法内部不存在理论误差。数值模拟结果表明：（1）一阶自傅立叶孤子对中的相互作用表现不同于一阶标准孤子对,它类似于二阶或准二阶孤子之间的相互作用特性。两孤子经历一段周期性的相互吸引后,出现强烈的相互排斥;（2）孤子相互作用特性不足以用孤子的阶去区分或分类,在同一阶的孤子中,不同的脉宽对孤子的相互作用有显著不同的影响;（3）微弱的三阶色散效应有利于抑制一阶自傅立叶孤子间的相互作用。     

Soliton transmission using periodic dispersion compensation

We examine the behavior of solitons in optical fibers where the dispersion is alternated between the normal and anomalous regimes. The periodic nature of the system strongly modifies the shape of the stable soliton (solitary wave) pulses, and increases their energy when compared with solitons in equivalent uniform fibers. Power enhancement factors of up to 70 are numerically observed. This leads to both an increased signal-to-noise ratio (SNR) at the receiver and reduced Gordon-Haus timing jitter. The interaction between pairs of isolated pulses is examined. We also examine implementations including periodic amplification, and show that the energy scalings introduced by the amplification and the dispersion management are independent provided that the periods of the two processes are dissimilar. We show that there is an optimum dispersion compensation ratio which minimizes the received Gordon-Haus jitter. A diagrammatic technique is presented for estimating the performance of dispersion compensated soliton transmission systems     

o偏振光对光折变屏蔽光伏空间孤子的影响

为了得到o偏振光对光折变屏蔽光伏空间孤子影响的结果,基于单光子光折变效应理论模型,建立了有分压电阻和o偏振均匀背景光辐照的光伏光折变晶体中的屏蔽光伏空间孤子理论。结果表明,当外加电场和光伏场的取值使晶体中形成暗孤子时,仅改变o背景光与孤子光的有效glass系数之比即可在晶体中获得明孤子;孤子的强度半峰全宽随o背景光强度与暗辐射强度比值的增大而增大,随o背景光与孤子光电离截面的比值的增大而增大。这从理论上为实现光折变晶体中暗孤子到明孤子的转换提供了一种全新的思路。     

有偏压光伏光折变晶体中低振幅非相干耦合孤子对

从理论上研究了有偏压的光伏光折变晶体中低振幅屏蔽光伏孤子对的特性，给出了明一明、暗一暗屏蔽光伏孤子对的单孤子解。它们起源于对外电场的非均匀空间屏蔽和光伏效应，不同于起源于对外电场非均匀空间屏蔽孤子和起源于光伏效应的光伏孤子，具有有趣的特性。当光伏效应可忽略时，它们的非线性波动方程就转化为低振幅屏蔽孤子对的非线性波动方程，它们就转化为低振幅屏蔽孤子对；当外偏压为零时，它们的非线性波动方程就转化为低振幅闭路和开路光伏孤子对的非线性波动方程，它们就转化为低振幅闭路和开路光伏孤子对。如果载体光束具有相同的偏振和波长以及互不相干时，这些孤子对就能得到，相关的例子在光伏光折变晶体铌酸锂(LiNbO3)中给出。     

脉冲内拉曼散射效应影响下高阶孤子之间的相互作用及其控制

在脉冲内拉曼散射效应影响下,研究了同相和反相相邻高阶孤子脉冲之间的相互作用,分析了孤子之间的相互作用对定时抖动的影响和脉冲内拉曼散射效应所引起的孤子脉冲频移.研究结果表明;在脉冲内拉曼散射效应的影响下,同相和反相高阶孤子脉冲对都发生了分裂,分裂出的两个较强的孤子脉冲在传输过程中发生碰撞,碰撞后两脉冲迅速分离;二者的不同之处在于反相孤子脉冲对分裂出来的两个较强脉冲之间的相互作用较弱,其碰撞距离明显远于同相孤子脉冲对.引入非线性增益可以有效控制孤子之间的相互作用,抑制孤子自频移效应,稳定孤子传输.     

Optical Solitons with Power Law Nonlinearity and Hamiltonian Perturbations: An Exact Solution

This paper studies the optical solitons with power law nonlinearity in presence of Hamiltonian perturbation terms. The perturbation terms that are taken into account are inter-modal dispersion, third order dispersion, self-steepening term and nonlinear dispersion. An exact 1-soliton solution is obtained by the solitary wave ansatz. Both bright and dark optical soliton solutions are obtained. The domain restrictions have also been identified in the process.     

Three-wave envelope solitons: possibility of controlling the speedof light in fiber

Theory predicts that three-wave envelope solitons (TWES) can he generated in dual-mode optical fibers by simultaneous injection of two copropagating optical modes. The mechanism of the three-wave interaction is the recently observed intermodal forward stimulated Brillouin scattering (FSBS). The dynamics of soliton generation depends on the duration of the injected pulses, the pump power, and the attenuation time constant. For the adiabatic modulation of injected optical waves, a new type of generation has been analyzed: an acoustical wave structure that scatters the incident pump into the Stokes wave is formed in the fiber prior to and after the soliton generation. This structure appears as a result of FSBS and serves as a TWES “launcher.” We identify this type of generation in earlier soliton experiments in stimulated Raman scattering. The TWES velocity depends on the pump power. For a typical dual-mode fiber, the speed of TWES can be adjusted over four orders of magnitude by adjusting the pump power between 0.01 and 200 mW. The duration of the soliton is <3 ms due to the acoustic attenuation. The length of the fiber can be shorter than the length of the soliton while preserving the same TWES characteristics. Both Ar⁺ and Nd:YAG lasers are suitable for TWES generation     

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。