双折射光纤中偏振模色散的抑制

利用双折射光纤中孤子自捕获现象可以抑制偏振模色散,但这种抑制技术对传输参量有严格的限制.本文提出在双折射光纤中周期性地改变快慢轴的方法来抑制偏振模色散. 研究发现,这种方法在一定程度上能有效地抑制偏振模色散,并且光纤间偏振轴的夹角偏差有利于对偏振模色散的进一步抑制.     

偏振模色散影响色散控制孤子传输的理论研究

采用变分法分析高速色散控制孤子在双折射光纤中的传输规律。首先建立了色散控制孤子在双折射光纤中的扰动传输模型 ,然后解析了偏振模色散影响下色散控制孤子各参量的传输演化规律 ,最后对解析结果进行了计算。研究结果表明 ,偏振模色散参量对色散控制孤子能量、脉宽的演化影响很大 ,当偏振模色散很大时 ,如Dp>0 .3ps/km1/ 2 时 ,必须考虑采用某些在线控制手段来有效抑制偏振模色散对传输系统的影响 ,然而 ,当Dp≤ 0 .1ps/km1/ 2 时 ,系统几乎不受影响 ,同时本文还证明了色散控制孤子抗偏振模色散扰动的能力强的这一特点。为研究偏振模色散对高速非线性传输系统、特别是色散控制孤子传输系统的影响提供了理论依据和研究方法。     

强双折射光纤中超短光脉冲压缩效应研究

研究了强双折射光纤中沿偏振主轴入射的超短光脉冲压缩效应。当考虑三阶色散效应时，三阶色散与光纤非线相互作用能增强一偏振光脉冲的压缩而抑制另一偏振光脉冲的压缩。正三阶和的强慢孤子压缩，负三阶色散增强快孤子压缩，三阶色散参量越大，脉冲压缩效果越明显。     

色散缓变光纤中的调制不稳定性分析

研究了色散缓变光纤中调制不稳定效应,得到了增益谱与光纤纵向色散参量的一般关系式.结果表明,色散缓变光纤较常规光纤具有较宽的增益谱.选取色散级变光纤的色散参量可以获得较大的增益带宽.数值模拟显示,利用色散缓变光纤中的调制不稳定性可以产生高重复率的基本孤子脉冲串.     

强双折射光纤中暗孤子的传输特性研究

从光纤双折射参量、背景光宽度、孤子脉冲宽度三方面探讨暗孤子在双折射光纤中远距离传输特性研究表明:相对于亮孤子,暗孤子对光纤双折射的自适应能力较弱;背景光宽度越大,暗脉冲与背景光对比度越好,暗孤子越能保持原来黑孤子状态;暗孤子脉冲宽度越大,偏振脉冲之间的差分群时延越大,诱导的灰孤子震荡结构越明显,越不利于暗孤子远距离传输.     

全正色散多波长被动锁模耗散孤子掺镱光纤激光器

报道了一种带有周期性双折射光纤滤波器的全正色散多波长被动锁模耗散孤子掺镱光纤激光器. 通过数值模拟发现加入滤波器后激光器能输出多波长耗散孤子脉冲, 调节滤波器带宽大小可以得到不同波长个数和波长间隔的多波长锁模耗散孤子脉冲. 在激光器产生的四波长和五波长耗散孤子脉冲中观察到了耗散孤子分子, 并且通过调节滤波器参数和饱和功率可以改变多波长脉冲中耗散孤子分子的个数和波长. 这是在被动锁模光纤激光器中首次实现包含有耗散孤子分子的多波长脉冲. 另外还在实验上实现了全正色散双波长被动锁模耗散孤子的产生. 关键词： 全正色散 耗散孤子 多波长脉冲 孤子分子     

双折射色散阶跃光纤中拉曼效应和参量放大增益谱

在拉曼效应和参量放大共同作用下,当激光脉冲在双折射光纤中传输时,根据所遵循的耦合模方程,通过引入平行拉曼增益的洛伦兹模型,导出了当输入泵浦波偏振方向同双折射轴成45°角时,在双折射色散阶跃光纤中拉曼效应和参量放大共同作用所导致的增益,讨论并分析了在不同色散区增益谱随相关参量的变化。结果表明:由于拉曼效应、参量放大、双折射和色散的相互作用,导致增益谱的斯托克斯波与反斯托克斯波彼此不对称;在反常色散区,产生的增益以反斯托克斯波为主,在正常色散区则以斯托克斯波为主;当表征距离的级数m发生变化时,增益谱也随之发生变化,可以利用色散阶跃光纤在适当的级数m位置提取T频率脉冲。     

反常色散平坦光纤产生平坦宽带超连续谱的数值研究

通过数值计算，对反常色散平坦光纤中高阶孤子压缩效应产生超连续谱进行了系统、深入的研究. 结果表明，反常色散平坦光纤的色散参量二阶微分常量、峰值色散参量及抽运脉冲的脉宽、孤子阶数对该种光纤中平坦超连续谱的形成及所需光纤长度的选取都有着非常重要的影响；进一步研究表明，超连续谱的展宽机理主要来自脉冲的自相位调制效应和群速度色散的共同作用,高阶非线性效应对超连续谱的产生不起决定性作用，在计算中完全可以忽略. 关键词： 反常色散平坦光纤 超连续谱 自相位调制效应 群速度色散     

类明孤子在光纤中传输特性的变分研究

应用变分法,研究了微扰对类明孤子在光纤巾非线性传输特性的影响,导出了类明孤子脉冲参量演化的动力学方程。它统一了在单模光纤、色散缓变光纤或色散控制光纤中类明孤子脉冲参量演化的动力学方程。在此基础上,计算了色散缓变光纤中的线性高阶色散微扰。结果表明：线性高阶色散对类明孤子脉冲的位置和相位有影响,而对振幅、宽度和啁啾没有影响;光纤色散缓变对类明孤子脉冲的所有参量均有影响。     

色散缓变光纤中宽带调制不稳定性谱的产生

本文报道色散缓变光纤中调制不稳定性效应研究.从非线性Schrodinger方程出发,获得了增益谱与纵向色散变化参量和光纤传输距离的一般关系.研究发现,色散缓变光纤中调制不稳定性的增益谱较常规光纤中的宽得多.调节光纤色散纵向变化参量,可以得到较宽的增益谱.该文的研究结果为光纤中利用调制不稳定性产生超短孤子脉冲提供了理论根据.     

Higher-order Gabitov–Turitsyn equation for solitons in optical fibers

The higher-order multiple-scale asymptotic analysis is carried out for the Gabitov–Turitsyn equation that governs the propagation of dispersion-managed solitons through optical fibers. The averaged equation, with the consideration of higher-order terms, provides an in-depth understanding of the soliton propagation through an optical fiber. The polarization preserving fibers as well as birefringent fibers are considered in this paper. Finally, the study is extended to the case of multiple channels, namely dispersion-flattened fibers.     

Perturbation of Super-Sech Solitons in Dispersion-Managed Optical Fibers

The dynamics of super-sech solitons in dispersion-managed optical fibers is obtained in this paper. The dynamical system of soliton parameters is obtained for such pulses for dispersion-managed fibers, in presence of various perturbation terms. The perturbation terms studied are Hamiltonian, as well as non-Hamiltonian along with non-local types.     

Simulative demonstration of soliton pulse stability over the nonlinear regime in a birefringent optical fiber

In this paper, the results of numerical analysis are demonstrated for sech pulse (soliton) propagation in a birefringent optical fiber using computer modeling and simulation. Here, the initial pulse is polarized linearly and guided into the fiber at an angle of 45° to its polarization axes. The birefringence-induced time delay of 200 and 440 ps between X and Y polarization components has been reported at a fiber length of 631.72 km (10 soliton periods) by considering linear and nonlinear regimes, respectively. The Kerr nonlinearity, which stabilizes solitons against spreading due to GVD, also stabilizes them against splitting due to birefringence. A similar fact is true for the birefringent walk-off. Above a certain soliton order (N_th), the evolution scenario is qualitatively different and two orthogonally polarized components of the soliton move with a common group velocity despite their different modal indices or polarization mode dispersion (PMD) at a fiber length of 631.72 km (10 soliton periods) and 1264.344 km (20 soliton periods) over a nonlinear regime at θ≠45°. The physical effect responsible for this type of behavior is the cross-phase modulation (XPM) between the two polarization components.     

Dispersion-managed soliton in optical fibers with zero average dispersion

A dispersion-managed optical system with stepwise periodic variation of dispersion is studied in the framework of a path-averaged Gabitov-Turitsyn equation. The soliton solution is obtained by means of iterating the path-averaged equation. The dependence of soliton parameters on dispersion map strength is investigated, together with the oscillating tails of the soliton.     

Dispersion-managed soliton in a strong dispersion map limit

A dispersion-managed optical system with stepwise periodic variation of dispersion is studied in a strong dispersion map limit in the framework of the path-averaged Gabitov-Turitsyn equation. The soliton solution is obtained by analytical and numerical iteration of the path-averaged equation. An efficient numerical algorithm for finding a DM soliton shape is developed. The envelope of soliton oscillating tails is found to decay exponentially in time, and the oscillations are described by a quadratic law.     

Phase jitter in periodically dispersion-managed optical transmission systems

We investigate the phase jitter in long-haul optical transmission systems with periodic dispersion management and amplification. We compare different dispersion-managed soliton systems and a conventional soliton system having the same pulse width and path-averaged dispersion. Using the variational method, we derive the ordinary differential equations for the pulse parameters perturbed by amplifier noise and hence calculate the phase jitter. We verify the analytical results by numerically solving the nonlinear Schrödinger equation using split-step Fourier algorithm. The results suggest that the reduction of nonlinear phase noise in dispersion-managed soliton systems is possible compared to a conventional soliton system. It is also revealed that the phase noise is enhanced in stronger dispersion-managed systems. We also explore the phase noise effect in dispersion-managed quasi-linear systems and find that phase jitter is mitigated in highly dispersive fibers.     

Persistent oscillations of scalar and vector dispersion-managed solitons

We show that both orthogonal and parallel internal modes exist on the background of a dispersion-managed (DM) soliton in randomly birefringent fibers. The orthogonal modes exist for arbitrarily small values of the dispersion map strength, while the parallel modes exist only when the map strength exceeds a certain threshold value. We demonstrate that initial perturbations of a DM soliton's profile that consist of one or more internal modes, exhibit nearly stable oscillations over very long propagation distances, before decaying into radiation. (c) 2000 American Institute of Physics.     

High-speed soliton transmission in dense periodic fibers

An 80-Gbit/s soliton can be transmitted over a cross-Pacific distance in a dense periodic fiber, even in the presence of higher-order effects. Such a dense dispersion-managed soliton is generally more stable and faces fewer mutual interactions than a conventional dispersion-managed soliton.