脉冲啁啾对相位共轭通信系统性能的影响

数值模拟了线性啁啾高斯脉冲在光纤中的传输演化过程,分析了线性啁啾高斯脉冲的传输特性。结果表明,脉冲啁啾不会影响中置相位共轭系统对色散和非线性效应导致的信号失真的完全补偿;单模光纤中啁啾将导致脉冲信号产生初期窄化和末期窄化过程,这种传输特性可用来优化相位共轭系统的总体结构设计,进一步改善和提高系统的补偿性能。     

两种相位共轭技术对光纤中超短光脉冲传输失真的补偿比较

通过理论分析和数值计算,比较了时域相位共轭技术和频域相位共轭技术对光纤中由于色散和非线性引起的超短光脉冲传输失真的补偿效果。结果表明,在仅考虑群速度色散和自相位调制效应时,时域相位共轭技术与频域相位共轭技术的补偿效果一致;当需要考虑三阶色散时,频域相位共轭技术的补偿效果优于时域相位共轭技术;当需要考虑脉冲内拉曼散射时,时域相位共轭技术的补偿效果优于频域相位共轭技术;当上述四种效应同时考虑时,频域相位共轭技术的补偿效果略优于时域相位共轭技术。同时还对上述两种补偿技术的应用进行了讨论。     

相位共轭技术对光纤中互相位调制效应的补偿研究

针对两束波长不同的信号脉冲的传输情况,通过理论分析和数值计算,研究了采用频域相位共轭技术和时域相位共轭技术分别对互相位调制效应的补偿情况.结果表明:时域相位共轭技术无法补偿互相位调制引起的信号失真,频域相位共轭技术则能完全补偿.对于高斯脉冲,经频域相位共轭技术补偿的输出与输入信号脉冲完全相同;对于不同啁啾值的高斯脉冲,...     

高阶效应对微结构光纤中超连续谱产生的影响

采用分布傅立叶方法求解了广义非线性薛定谔方程（GNSE）,数值模拟了飞秒激光脉冲在微结构光纤中的非线性传输和超连续谱的产生,详细分析了脉冲拉曼散射、自陡峭效应以及三阶色散对超连续光谱产生的影响。分析结果表明：超短脉冲在微结构光纤中传输时出现孤子自频移现象,同时也发现脉冲内拉曼散射和自相位调制的联合作用导致高阶孤子分裂,光谱得到极大展宽,在时域中出现两个滞后的拉曼孤子,三阶色散和自陡效应对光谱的形状影响较小,起着与脉冲内拉曼散射相反的作用,自陡效应比三阶色散效应对光脉冲的影响大一些。     

高速光纤传输系统中三阶色散效应影响研究

利用OptiSystem软件,对高速光纤传输系统中三阶色散(TOD)导致的脉冲失真进行了仿真研究。分析了光脉冲信号通过光纤传输系统传输2000 km,不同的速率、占空比、脉冲形状和光纤类型对三阶色散的影响,同时比较了高斯脉冲和超高斯脉冲经过2000 km传输后的品质因数,发现高斯脉冲的品质因数优于超高斯脉冲的品质因数。通过仿真分析得出:当同时考虑群速度色散(GVD)和三阶色散的时候,标准单模光纤(SSMF)和啁啾光纤布拉格光栅(CFBG)组成的高速光纤传输系统性能表现较好。     

离散效应对光子晶体光纤中飞秒脉冲压缩影响

为了研究离散效应对光子晶体光纤中飞秒信号脉冲压缩的影响,采用分步傅里叶方法数值求解耦合的非线性薛定谔方程,模拟了双飞秒脉冲在光子晶体光纤中的非线性传输过程;计算和分析了离散效应和非同步耦合对信号脉冲压缩的影响。结果表明,当抽运脉冲在反常色散区进行抽运,而信号脉冲在正常色散区入射时,在群速度色散、3阶色散,自相位调制及交叉相位调制联合作用下,信号脉冲在传输过程中不仅被压缩且存在最佳光纤长度;离散效应导致信号脉冲压缩因子减小,所需最佳光纤长度增加以及压缩后的脉冲频谱呈现不对称,采用非同步耦合有利于改善信号脉冲的压缩质量。     

基于OPC的高速PDM-CO-OFDM系统研究

通过理论分析和数值仿真,搭建了100Gbit/s的PDM(偏振复用)-CO-OFDM(相干光正交频分复用)系统,并使用OPC(光学相位共轭)技术对100Gbit/s的PDM-CO-OFDM系统的传输性能进行了补偿。研究表明,相位共轭技术不仅能够补偿系统的各阶色散,还能补偿非线性效应,使用OPC技术能使系统的传输距离达到1 200km,在最佳补偿距离上,使用OPC的系统Q值比使用传统的DCF(色散补偿光纤)的系统Q值大6.3dB。     

光子晶体光纤中双脉冲非线性传输的数值分析

采用分布傅立叶方法数值求解耦合的非线性薛定谔方程,模拟了双脉冲在光子晶体光纤中的非线性传输过程,计算和分析了离散效应和脉冲内拉曼散射对信号脉冲传输和压缩的影响。结果表明,当中心波长为800nm的泵浦脉冲在反常色散区进行泵浦,而中心波长为740nm的信号脉冲在正常色散区入射,在群速度色散,自相位调制及交叉相位调制联合作用下,信号脉冲在传输过程中不仅被压缩且存在最佳光纤长度。离散效应不仅导致脉冲压缩比的减小和压缩后峰值功率的降低,而且导致脉冲所需最佳光纤长度的增加以及压缩后的脉冲呈现不对称,还发现,脉冲内拉曼散射有利于改善脉冲压缩质量。     

三阶色散对光纤中基孤子脉冲传输的影响

通过数值求解非线性薛定谔方程,研究了三阶色散效应对基孤子脉冲在单模光纤中传输的影响.结果表明,在三阶色散作用下,基孤子脉冲在传输过程中被展宽,峰值能量逐渐减小,脉冲形状发生畸变,脉冲的中心偏向一侧,并形成非对称的拖尾振荡结构;当与二阶色散共同作用时,三阶色散引起的脉冲振荡会变缓.考虑非线性效应后,在一定程度上补偿了由于色散效应导致的峰值功率的减小,同时抑制了非对称拖尾结构的产生.     

色散补偿系统中自相位调制效应的影响

分析了自相位调制效应对正、负色散光纤中光脉冲传输的影响 ,并用数值仿真的方法研究了自相位调制效应对采用色散补偿光纤的高速率光纤通信系统性能的影响 ,获得了一些对实际色散补偿系统有参考价值的结论。     

Compensation for the self-steepening effects in optical fiber communication system using midway optical phase conjugation

Effects of self-steepening (SS) of chirped Gaussian pulses on optical fiber communication system using midway optical phase conjugation (OPC) are analyzed. Dynamic evolution of the ultrashort pulses is simulated numerically. It is found that OPC cannot compensate for pulse waveform distortion due to SS.The initial chirp of pulses and dispersion can counteract SS and improve the compensation performance for the distortion.     

啁啾光脉冲在高阶色散控制光纤链中的稳定传输

基于一种二阶和三阶色散补偿的光纤级联系统模型 ,用数值法对啁啾皮秒光脉冲作了传输模拟。结果表明 ,完全补偿的高阶色散控制系统消除了三阶色散所引起的脉冲边沿部的振荡 ,减弱了脉冲峰的时间移动 ;另外 ,在确定的配置下 ,给输入脉冲附加一最佳的频率啁啾 ,可使得色散控制孤子稳定传输。脉冲宽度和啁啾以及光强度都围绕在初始值附近波动 ,在每个补偿周期末端 ,基本恢复到初始值 ;最佳啁啾的选取与二阶色散的配置有关 ,与三阶色散的配置无关 ;文中画出了 10 0Gbit/s码率的 64位随机高斯光脉冲序列在完全补偿系统中传输 10 0 0 0km后的眼图。由清晰的眼图可知 ,这种完全补偿系统减弱了脉冲之间的相互作用     

Optical phase conjugation of multiwavelength signals in adispersion-shifted fiber

Optical phase conjugation (OPC) of multiwavelength signals in a dispersion-shifted fiber (DSF), which can be used for dispersion compensation in the wavelength division multiplexing communication system, is theoretically studied. The multiwavelength phase-conjugate signals are generated by four-wave mixing (FWM) in the dispersion-shifted fiber. There are the pulse-shape distortion and the induced frequency chirping in the phase-conjugate signals owing to pump depletion and the cross-phase modulation among the signals and phase-conjugate signals, respectively. The FWM among the pump wave, signals, and phase-conjugate signals causes unequal conversion efficiencies for the multiwavelength signals and enhances the induced frequency chirping in the phase-conjugate signals. The induced frequency chirping may deteriorate the restoration of the pulse shape. Both the pulse-shape distortion and induced frequency chirping increase with the signal and pump powers. The formula for the induced frequency chirping that is only caused by the signals through cross-phase modulation is derived. The requirement of the signal power in the dispersion-shifted fiber for the restoration of the pulse shape by the optical phase conjugation is estimated and numerically verified     

Generation of optical phase-conjugate waves and compensation forpulse shape distortion in a single-mode fiber

The generation of optical phase-conjugate waves and the application of optical phase conjugation (OPC) to optical communication systems is described. The method of pulse shape distortion compensation by OPC is outlined including distortion due to both fiber dispersion and the optical Kerr effect. The generation of a forward-going phase-conjugate wave in a third-order nonlinear medium is discussed and that by a nondegenerate forward four-wave mixing in a zero-dispersion single-mode fiber (SMF) is investigated. Suppressing the stimulated Brillouin scattering (SBS) of a pump wave in the fiber prevents saturation of the generation efficiency of the phase-conjugate wave even when the pump power exceeds the SBS threshold. In transmission experiments through a 200-km standard SMF with a 16-Gb/s intensity-modulated signal and a 5-Gb/s continuous-phase FSK (CPFSK) modulated signal, it is shown the applicability of OPC is modulation independent and that OPC effectively compensates for both chromatic dispersion and the optical Kerr effect     

色散对光纤中高斯光脉冲传播特性的影响

从麦克斯韦方程组出发,建立了光脉冲在光纤中传播的理论模型。在只考虑色散效应的情况下,对该理论模型进行进一步的研究,数值模拟出高斯光脉冲在光纤中的传输状态,并讨论了色散对光脉冲传播特性的影响。结果表明,群速度色散会增加光脉冲的宽度而波形保持不变;三阶色散会引起光脉冲的畸变。该结论对光纤的色散补偿具有一定的理论参考价值。     

Limitations on peak pulse power, pulse width, and coding maskmisalignment in a fiber-optic code-division multiple-access system

The authors analyze the effects of fiber dispersion and optical nonlinearity on a code-division multiple-access (CDMA) communications system. They assume that each transmitter has a unique phase-encoding mask to scramble the pulses, and that the intended receiver has the complementary phase-decoding mask to unscramble the pulses. The necessary nonlinear pulse propagation equation is derived using a new and systematic approach. The authors then determine the minimum allowable pulse width and the maximum pulse width for the system. They next calculate the maximum optical power, which is limited by the fiber's self-phase modulation. This power is significantly larger than the minimum detectable optical power determined by the noise in the electrical receiver, so that in practice any distortion caused by the fiber's optical nonlinearity can be avoided. From their calculations estimates for all important optical parameters are provided. The deleterious effect of a slight relative misalignment between the encoding and decoding masks is also investigated     

Exact compensation for both chromatic dispersion and Kerr effect ina transmission fiber using optical phase conjugation

We propose a new method to compensate exactly for both chromatic dispersion and self-phase modulation in a transmission fiber, where the light intensity changes due to fiber loss and amplifier gain. This method utilizes optical phase conjugation (OPC). The pulse shape is precompensated before OPC by transmission through a fiber with large dispersion. A computer simulation demonstrates effective compensation for waveform distortion in a 40 Gb/s NRZ intensity-modulated light transmission     

Pulse propagation in fibers with polarization-mode dispersion

The propagation of pulses in optical fibers with polarization mode dispersion (PMD) is considered. The approach taken differs from those previously used, adapting Marcuse's perturbation method to analyze pulse dispersion rather than using Jones matrices or Stokes parameters. This allows the complex stochastic partial differential equations to be reduced to a simple propagation equation for the pulse power. This may be solved to obtain the transfer function of the fiber. The impact of PMD on optical fiber communications systems is considered, with the effect on pulsewidth and eye closure calculated. Finally, the statistical behavior of the phenomenon is considered to calculate the system outage probability due to PMD     

光纤波导中光脉冲演化方程的数值解及计算机仿真研究

在光纤通信中，光脉冲信号在光纤中传输的过程中会受到色散、损耗和非线性等作用的影响而不断地发生演化和畸变。脉冲演化的规律遵循非线性薛定谔方程（NLSE）。由于NSLE在一般情况下无法求得它的解析解，因此通常需采要用数值方法来求解。本文使用了分步傅里叶方法对NLSE进行了求解，并用利用这一结果对四种常见的光通信光脉冲在光纤中传输时的演化情况进行了计算机仿真研究，仿真结果分别模拟了几种常见光脉冲在光纤中传输时包络的演化情况。