Dynamically Stable Solitons in Optical Fibers

The existence of a dynamically stable soliton in optical fibers is established by virtue of the multiple-scale perturbation technique applied in a new way to the perturbed nonlinear Schrodinger's equation. We show that, by introducing a proper definition of the phase of the soliton, one can obtain the corrections to the pulse where the standard soliton perturbation approach fails.     

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.     

Optical soliton perturbation with Raman scattering and saturable amplifiers

The method of multiple-scale perturbation is developed to study the propagation of solitons through an optical fiber described by the perturbed nonlinear Schrödinger's equation. We show that, by introducing a proper definition of the phase of the soliton, one can obtain the corrections to the pulse where the usual soliton perturbation approach fails. A comparison is made with results obtained by other methods as well as with numerical simulations.     

10 Gbps optical soliton transmission link using in-line SOA on standard SMF at 1.3 μm

In this paper, 10 Gbps optical soliton transmission link using in-line semiconductor optical amplifiers (SOAs) for already installed standard single mode fibers (SMF) at 1.3 μm wavelength has been reported. The pattern effect and the impact of chirp on pulse propagation after amplification have been investigated. The observations are based on modeling and simulation optical soliton transmission link. Optical soliton pulse transmission over distances of the order of several hundreds of kilometers has been shown with and without initial chirp.     

Collisions and turbulence in optical rogue wave formation

We discuss optical rogue wave generation in terms of collisions and turbulence processes. Simulations of picosecond pulse propagation in optical fibres show rogue soliton generation from either third-order dispersion or Raman scattering independently. Simulations of rogue soliton emergence with dispersive perturbation in the long-distance limit are also presented.     

Dark-in-the-Bright solitary wave solution of higher-order nonlinear Schrödinger equation with non-Kerr terms

We present new type of Dark-in-the-Bright solution also called dipole soliton for the higher order nonlinear Schrödinger (HNLS) equation with non-Kerr nonlinearity under some parametric conditions and subject to constraint relation among the parameters in optical context. This equation could be a model equation of pulse propagation beyond ultrashort range in optical communication systems. The solitary wave solution is composed of the product of bright and dark solitary waves. This type of pulse shape to be formed both the group velocity dispersion and third-order dispersion must be compensated. We also investigated the stability of the solitary wave solution under some initial perturbation on the parametric conditions. We have shown that the shape of pulse remains unchanged up to 20 normalized lengths even under some very small violation in parametric conditions.     

Propagation of bright femtosecond pulses in a nonlinear optical fibre with the third- and fourth-order dispersions

We solve the generalized nonlinear Schr\"{o}dinger equation describing the propagation of femtosecond pulses in a nonlinear optical fibre with higher-order dispersions by using the direct approach to perturbation for bright solitons, and discuss the combined effects of the third- and fourth-order dispersions on velocity, temporal intensity distribution and peak intensity of femtosecond pulses. It is noticeable that the combined effects of the third- and fourth-order dispersions on an initial propagated soliton can partially compensate each other, which seems to be significant for the stability controlling of soliton propagation features.     

Soliton formation in the propagation of phase-modulated femtosecond pulses through an optical fiber with a cubic nonlinearity

A way of soliton self-formation upon propagation of femtosecond light pulses through an optical fiber with a cubic nonlinearity is described with allowance for the dispersion of the nonlinear response of the medium. For soliton formation to occur, a low-frequency phase modulation of the initial pulse is necessary. Several solitons formed in this way differ in both maximal intensities and group velocities. The duration of an individual soliton may be several (up to ten) times smaller than the initial duration of the input pulse.     

Dynamics of solitons in periodic systems with different nonlinear media

To analyze pulse dynamics in an optical system consisting of a periodic sequence of nonlinear media, a composite model is used. It includes a model of the resonance interaction of an ultrashort light pulse with the energy transition of the medium with allowance made for an upper level pump and an almost integrable model that describes the propagation of the light field in the other medium with a cubic nonlinearity and dispersion. Additional allowance is made for losses and other kinds of interaction by introducing perturbation terms. On the bases of the inverse scattering transform and perturbation theory, a simple method for analyzing specific features of soliton evolution in periodic systems of this kind is developed. It is used to describe various modes of soliton evolution in such a system, including chaotic dynamics.     

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.     

中红外可调谐大能量飞秒脉冲激光产生

可调谐中红外飞秒光纤激光器具有非常普遍的应用,从而引起了人们的广泛关注。目前,非线性光纤中的拉曼孤子自频移效应是实现大范围可调谐飞秒脉冲激光的理想方法之一。然而,非线性光纤中其他高阶非线性效应的产生通常会限制拉曼孤子脉冲的能量提升。本文提出了利用有源掺杂光纤作为非线性介质和增益介质实现可调谐大能量中红外飞秒激光脉冲的方法。在理论上研究了有源掺杂非线性光纤中高阶孤子劈裂和孤子自频移效应的产生,以及线性增益对波长移动拉曼孤子能量、脉宽、光谱的影响。结果表明,通过为波长红移的低能量拉曼孤子提供线性增益,孤子脉冲的能量得到了显著提升且保持了其单脉冲特性,脉冲宽度为45 fs,且孤子脉冲的波长可通过所提供的增益进行大范围调谐。因此,利用有源掺杂光纤作为非线性介质是实现大能量可调谐中红外飞秒脉冲激光的一种有效方法。     

光纤中基于拉曼放大与脉冲压缩的超短光孤子产生

提出一种在单模光纤负群速色散枢由弱脉冲产生高强度超短光孤子的新方法。     

连续波微扰下飞秒光孤子的传输特性研究

给出了描述连续波扰动下飞秒光脉冲在光纤系统中传输的微扰高阶非线性薛定谔方程,通过矩法和微扰理论分析了飞秒亮孤子与连续波相互作用的特性,并利用龙格-库塔积分和分步傅里叶方法进行了数值模拟.结果表明,连续波微扰对光纤孤子通讯系统是十分有害的,在实际通讯过程中应当尽量避免连续波的渗入.     

Evolution of optical pulses in the presence of third-order dispersion

We model the propagation of femtosecond pulses through optical fibres by a nonlinear Schrödinger (NLS) equation involving a perturbing term arising due to third-order dispersion in the medium. The perturbative effect of this higher-order dispersion causes the usual NLS soliton to emit a radiation field. As a result, the given initial pulse propagating through the fibre exhibits nonsolitonic behaviour. We make use of a variational method to demonstrate how an initial pulse by the interaction with the emitted radiation can evolve into a soliton. We also demonstrate that the effect of interaction between the initial pulse and radiation field can be accounted for by including, in the evolution equation, terms associated with self-steepening and stimulated Raman scattering that characterize the optical medium.     

Evolution of Hyperbolic-Secant Pulses Towards Cross-Phase Modulation Induced Optical Wave Breaking and Soliton or Soliton Trains Generation in Quintic Nonlinear Fibers

The approximate analytical frequency chirps and the critical distances for cross-phase modulation induced optical wave breaking(OWB) of the initial hyperbolic-secant optical pulses propagating in optical fibers with quintic nonlinearity(QN) are presented. The pulse evolutions in terms of the frequency chirps, shapes and spectra are numerically calculated in the normal dispersion regime. The results reveal that, depending on different QN parameters, the traditional OWB or soliton or soliton pulse trains may occur. The approximate analytical critical distances are found to be in good agreement with the numerical ones only for the traditional OWB whereas the approximate analytical frequency chirps accords well with the numerical ones at the initial evolution stages of the pulses.     

影响光孤子传输的因素分析和可能的解决方案

从光孤子传输所满足的非线性薛定谔方程出发,通过对方程中参数的分析和选择,对影响孤子传输的各种因素采用单独分析和综合分析对比方法得到了两个新的结论:(1)二阶色散参数在不太大的范围内变化只会影响脉冲的幅值,对脉冲形状影响不大,而输入脉冲的啁啾则是使脉冲发生畸变的主要原因;(2)在啁啾、三阶色散和五阶非线性同时存在的情况下,它们对脉冲都会产生很大的影响,且存在相互影响和制约关系,三者在某一参数值附近,对脉冲却存在着增益效应和"整容"作用。针对分析结果从理论上提出了改进光孤子传输特性的解决方案,这对光孤子通信的实践过程是有一定实际意义的。     

Evolution of Hyperbolic-Secant Pulses Towards Cross-Phase Modulation Induced Optical Wave Breaking and Soliton or Soliton Trains Generation in Quintic Nonlinear Fibers

The approximate analytical frequency chirps and the critical distances for cross-phase modulation induced optical wave breaking (OWB) of the initial hyperbolic-secant optical pulses propagating in optical fibers with quintic nonlinearity (QN) are presented. The pulse evolutions in terms of the frequency chirps, shapes and spectra are numerically calculated in the normal dispersion regime. The results reveal that, depending on different QN parameters, the traditional OWB or soliton or soliton pulse trains may occur. The approximate analytical critical distances are found to be in good agreement with the numerical ones only for the traditional OWB whereas the approximate analytical frequency chirps accords well with the numerical ones at the initial evolution stages of the pulses.     

Soliton compression in quadratic media: high-energy few-cycle pulses with a frequency-doubling crystal

We present a soliton effect pulse compression technique that uses self-defocusing cascaded-quadratic nonlinearities, with no fundamental limit to its scalability to high pulse energies and the capability of generating few-cycle pulses with only a frequency-doubling crystal. The conditions for which group-velocity mismatch causes an acceptable perturbation to soliton compression are analyzed and underlie optimization of the compressor. Calculations predict compression to near-single-cycle durations, with compression ratios as high as 100. Initial experiments closely agree with calculations, demonstrating compression to durations under three optical cycles (12 fs) and generation of 600 nm bandwidths.     

有限宽度背景中的啁啾灰孤子

基于在正常色散区的变系数非线性薛定谔方程,考虑一个带有微扰的参数渐减光纤系统,并利用数值模拟方法,对超高斯型有限宽度背景波和有限宽度背景中啁啾灰孤子的传输进行详细地研究.结果表明,超高斯背景波可以在带有微扰的参数渐减光纤系统中不受负载啁啾灰孤子的影响而稳定传输.当取背景波脉宽与啁啾孤子的初始脉宽比例大于或等于50时,有限宽度背景中啁啾灰孤子的数值结果基本与精确解相吻合.即使选取的背景波脉宽不宽,有限宽度背景中的啁啾灰脉冲仍可以很好的保持其孤子性质.     

Dark soliton interaction in optical time division multiplexed system with randomly varying birefringence and random dispersion map

Correlated perturbations caused by both randomly varying birefringence and random dispersion map are considered in optical time division multiplexed dispersion-managed dark soliton system, and their effects on soliton interaction are investigated numerically. These perturbations enhance soliton interaction, and their effects relate to the strength of perturbation, separation, and pulse width. The correlation plays an important role and reinforces these effects. Moreover, there is a stochastic limit between two perturbations in the system, where the effect is the largest and the corresponding interaction distance is the shortest.