用正常色散的双折射光纤所作的暗孤子开关的开关条件

在正常色散的双折射光纤中传输的暗孤子对之间由于耦合周期性交换能量，一个暗孤子可把能量完全转给另一暗孤子，因此双折射光纤可作光开关。本文讨论了椭圆角为３５°的双折射光纤的开关条件，发现脉冲只有以特定的极化角入射才有开关现象产生，而且建立了光纤长度与孤子对相差、初始能量差的解释关系     

孤子色散管理传输及其在常规光纤通信中的可行性研究

从描述光纤中孤子脉冲传输的非线性薛定谔（NLS）方程出发，利用对称分步傅里叶方法对方程进行数值求解．研究了色散管理孤子（DMS）在常规光纤中的传输演化特性，分析了色散管理孤子在常规光纤通信系统中的可行性．结果表明，孤子在通过密集周期性搭配具有相反色散系数的光纤中传输，可以降低孤子间的相互作用，使得孤子的传输演化特性得到改善．利用色散管理来对常规光纤中光孤子脉冲之间的相互作用加以抑制，从而提高信息传输的比特率，但必须具有特殊的光纤制造工艺．     

光纤的暗孤子传输特性研究

本文用行波法求解了光纤的暗孤子的NLS方程,由此孤子解讨论了暗孤子在光纤中的传输特性。     

光纤孤子通信

本文简述光纤孤子的基本概念、光纤孤子传输理论以及光纤孤子在光纤传输过程中存在的若干问题和解决的办法。最后介绍有代表性的光纤孤子通信试验系统。     

光孤子传输演化的分步傅里叶法研究

光孤子传输的数值仿真研究对其实用化及系统设计具有重要意义。本文详细介绍了分步傅里叶法的基本原理和仿真步骤，并用Matlab语言对光孤子在光纤中的传输演化进行了仿真。讨论了光纤损耗对光孤子传输的影响,并说明当光孤子对在光纤中传播时，距离太近将会产生强烈的相互作用，导致孤子形状发生畸变。最后对掺铒光纤放大器对孤子能量补偿作用做了探讨，指出光孤子通信中主要是色散受限，采用980 nm光源泵浦的EDFA具有较好的效果。     

随机双折射对光孤子传输影响的研究

利用对称分步傅里叶法,数值模拟了光孤子在双折射光纤中的传输特性,分析了孤子脉冲两正交偏振分量的群速度失配对孤子传输产生的影响.结果表明,当光纤的双折射较小时,两偏振分量的脉冲强度变化不大,孤子基本能够保形传输;当光纤的双折射较大时,两偏振分量脉冲很快展宽,强度迅速减小,孤子不能够保形传输;如果光纤的双折射具有随机性,孤子传输的两偏振分量脉冲强度会随着传输距离有强弱不规则的变化,但是两偏振分量的强度变化互相补充,合成强度没有太大的变化,孤子能够稳定的传输;孤子间没有相互作用影响的传输距离随着光纤随机双折射偏振分量群速失配的增大而变小;通过选择恰当的振幅比,传统的不等振幅法仍然能够有效地抑制孤子间的相互作用.     

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.     

随机双折射对光孤子传输影响的研究

利用对称分步傅里叶法,数值模拟了光孤子在双折射光纤中的传输特性,分析了孤子脉冲两正交偏振分量的群速度失配对孤子传输产生的影响.结果表明,当光纤的双折射较小时,两偏振分量的脉冲强度变化不大,孤子基本能够保形传输|当光纤的双折射较大时,两偏振分量脉冲很快展宽,强度迅速减小,孤子不能够保形传输|如果光纤的双折射具有随机性,孤子传输的两偏振分量脉冲强度会随着传输距离有强弱不规则的变化,但是两偏振分量的强度变化互相补充,合成强度没有太大的变化,孤子能够稳定的传输|孤子间没有相互作用影响的传输距离随着光纤随机双折射偏振分量群速失配的增大而变小|通过选择恰当的振幅比,传统的不等振幅法仍然能够有效地抑制孤子间的相互作用.     

非线性光纤方向耦合器孤子动力特性分析

利用变分方法,导出了双曲正割型光孤子在非线性光纤耦合器中传输时满足的动力学方程组,分析了该方程组的平衡点性态,讨论了光孤子的开关特性.指出参数|β|<2π.是能实现完全的开关操作的必要条件.     

双环、三纤互耦全光纤熔锥滤波器用正常色散的双折射光纤所作的暗孤子开关的开关条件

通过将熔锥结构中强、弱耦合段的总幅度耦合系数与滤波网络方程中的幅度耦合系数等效的方法,定量分析了双环、三纤互耦滤波器的频谱特性。实验滤波器通带特性的测试结果与理论分析基本吻合。所测滤波器的中心波长、抑制度、半功率带宽及插入损耗分别为1.27 μm,>13 dB、72 μm及3.9 dB。在正常色散的双折射光纤中传输的暗孤子对之间由于耦合周期性交换能量,一个暗孤子可把能量完全转给另一暗孤子,因此双折射光纤可作光开关。本文讨论了椭圆角为35°的双折射光纤的开关条件,发现脉冲只有以特定的极化角入射才有开关现象产生,而且建立了光纤长度与孤子对相差、初始能量差的解释关系。     

Influence of the Magnetoelastic Mechanism on the Switching-field Fluctuations of Fe-based Amorphous Microwires

Experimental switching-field fluctuations on Fe-rich amorphous microwires have been studied at different temperatures. Two processes have been identified to be responsible for the temperature dependence of the switching field: Magnetostrictive volume domain-wall pinning and relaxation effects due to structural rearrangements A simple model accounting for two energy contributions to the switching-field has been used to fit experimental data. The switching field distribution and its unusual temperature dependence is solved in terms of a thermoactivated model. The distribution width is found to be proportional to the switching field.     

Switching characters of asymmetric ferroelectric films

The switching property of asymmetric ferroelectric films has been studied from Landau free energy and the Khalanikov mation. The polarization response and switching current under a step electric field and pulsed field have been investigated. Watching times, for both the up-switching and down-switching process, have been obtained and discussed.     

Current induced exchange switching of magnetic junctions with cubic anisotropy of a free layer

The stability of equilibrium configurations of magnetic junctions with a free layer of cubic anisotropy with two axes in the layer plane has been analyzed. Variants of switching between different configurations have been considered. It has been demonstrated that the possibility exists of considerably decreasing the threshold current density necessary for switching. Numerical simulation of the dynamics of switching between different configurations has been performed.     

Influence of fatigue processes on the switching currents in lead titanate and lead zirconate-titanate films

The processes of polarization fatigue in PbTiO₃ and Pb(Zr_0.5Ti_0.5)O₃ films on silicon substrates have been studied by the method of switching in rectangular pulsed fields. Dependences of the switchable polarization, the maximum switching current i _max, and the switching time ??s on the number of switching cycles have been obtained from the data on the switching currents. It has been shown that the mobility of domain walls is retained in the fatigue processes and the observed fatigue is connected with switching off a fraction of the switchable volume due to pinning of reverse domain nuclei by charged defects.     

Switching characteristics of silver-silicon monoxide superlattices

Layer structures of successive silver and silicon monoxide layer pairs were made using evaporating techniques. Small angle X-ray diffraction and multiple reflection interferometric techniques have been used to establish the identity periods of the samples. these samples were found to have switching characteristics. Slow and fast switching was observed and the application of voltage would induce switching into higher as well as into lower resistance states. Sequential switching through multiple resistance states has also been observed.     

Iron-yttrium garnet films with magnetic vortices

Submicron iron-yttrium garnet films have been studied. The effect of the switching of nonreciprocal resonance absorption, which is caused by the switching of the polarization of vortices, has been revealed.     

A comparative numerical study of soliton switching in a nonlinear directional coupler with saturating nonlinearity

A detailed numerical study of soliton switching in a nonlinear directional coupler with saturating nonlinearity is carried out. All commonly used models have been studied. Relevant physical characteristics for switching have been determined, compared and discussed.     

Picosecond GaP switches

Laser-activated GaP switching devices have been shown to provide voltage pulses ～5 kV with picosecond response and recovery times ～60–500 ps. Single and two-phonon photoconductivity processes have been inferred to explain the nature of the switching characteristics.     

Photoinduced semiconductor-metal phase transition and switching wave in the vanadium dioxide film

A switching wave has been studied in the VO₂ film during the photoinduced semiconductor-metal phase transition. The dependences of the critical radiation intensities corresponding to the direct and reverse phase transitions on the ambient temperature have been obtained in the framework of the thermal model. The profile and velocity of the switching wave have been calculated. The calculated data are compared with the experimental data.     

Polarization switching in perforated ferroelectric films

The polarization switching in ferroelectric films of barium strontium titanate with a planar structure of interdigitated electrodes has been studied experimentally. The local polarization distribution in an interelectrode gap of these films in an applied electric field has been investigated using nonlinear optical microscopy. The polarization switching parameters of unperforated and perforated films have been compared.