多信道WDM系统非线性相位噪声的研究

利用在频率范围内的噪声传输函数研究当色散主导和非线性主导时非线性相位噪声传输,并基于多信道多光纤段的WDM系统,利用LEM-SSFM数值方法计算非线性光纤系统的SNR,从传输距离,信号功率和放大器的数量三个角度研究非线性相位噪声的传输及其对系统性能的影响。     

WDM系统中的非线①性研究及仿真实验

利用分离信道的分步傅立叶法对信道间距为0.8nm的8路10 Gbit/s波分复用色散补偿系统进行仿真实验，分析了在具有级联光放大器系统中光纤色散和各种非线性效应（自相位调制SPM、交叉相位调制XPM、四波混频FWM）对系统传输的影响。仿真结果表明，在色散补偿WDM通信系统中，SPW对系统传输造成的损伤最大。并且由于非线性效应、传输损耗及噪声的综合影响，应当选取合适的系统输入功率。     

基于高非线性光纤四波混频的全光纤波长变换

对光纤四波混频(FWM)效应的相位匹配条件进行了分析，并针对两种利用光纤FWM进行波长变换的具体方案进行了讨论，指出利用高非线性光纤的FWM是一种简单可行的波长变换技术，并对此项技术目前存在的难点问题进行了探讨。     

基于非线性分离模型的四波混频噪声分析

基于OptiSystem软件平台提出了一种关于FWM(四波混频)噪声对系统性能影响程度进行评估的非线性分离模型,同时提出了一种新型的色散图。利用该模型对同偏振态33信道DWDM(密集波分复用)系统的FWM噪声进行了仿真。仿真结果表明,在给定的系统条件下,所有信道都采用DPSK(差分相移键控)调制的纯DPSK系统比采用DPSK-OOK(开关键控)混合调制的系统有更好的非线性容限。对于新型色散管理系统,当单信道速率和入射光功率较大时,DPSK-OOK的混合调制系统与纯DPSK调制系统相比,FWM噪声对系统性能影响更大。     

WDM系统中色散的实时监测

简单地推导了相位调制下的单音频率在传输光纤中其功率与光纤色散、光纤距离之间的关系，并介绍了在DWDM系统中可以利用相位调制法进行实时监测色散。此方法对于40GHz系统的色散实时监测提供了很好的参考方法。仿真结果表明，在未考虑光纤非线性效应的情况下有很高的精确性，当考虑非线性效应时，其传输距离会由于传输速率的影响而受到限制。     

光纤系统中的普适弱调制传输矩阵及其在噪声演化分析中的应用

本文在总结文献中已有工作的基础上,给出了光纤传输系统中普适的频域弱强度/相位调制的传输矩阵 H ,包含了光纤中各阶色散、非线性和光纤损耗的影响.指出奇数阶色散仅对矩阵分量的幅频特性产生影响,而偶数阶色散仅对矩阵分量的相频特性产生影响.因此,对弱强度/相位调制(噪声)而言,只有奇数阶色散才起作用.基于 H 矩阵,定量计算了分别用于强度探测系统、相位探测系统和光谱仪测量的强度噪声谱、相位噪声谱和光场噪声谱.     

基于QPSK的CO-OFDM传输系统研究

在对CO-OFDM系统和恒定包络调制技术进行了深入研究之后,将QPSK恒定包络调制技术引入了CO-OFDM系统中,从而提高系统性能,减少光纤非线性效应、载波频率偏移以及相位噪声对系统性能的影响.本文基于Optysystem软件搭建了传输速率为112 Gbit/s的仿真系统,并对设计方案进行了仿真验证.     

空间激光通信网络中的全光相位再生技术

围绕空间激光通信网络中高速数据多跳传输应用需求,针对相位调制激光链路经过空间长距离传输后信号质量劣化的问题,研究了基于相位敏感四波混频参量效应实现二进制相位调制高速激光信号的全光相位再生技术。利用Matlab软件数值分析了全光相位再生系统的影响因素,并基于OptiSystem仿真平台搭建了全光相位再生系统。结合高轨-地面站空间激光通信系统链路预算,对速率为10 Gbit/s的DPSK信号光经背靠背、相位噪声劣化以及劣化后全光相位再生处理三种传输场景进了对比分析。模拟仿真结果与数值分析结果均表明,与劣化后未经再生处理的系统相比,全光相位再生处理后的系统误码率平均优化4个数量级,信噪比提升约3 dB,表明该空间激光通信全光相位再生技术可实现相位调制信号的全光相位再生,能够有效提升空间相干激光通信系统的性能,可以应用于空间高速激光通信网络中继节点处的全光数据中继等方向。     

一种基于改进DD-RLS的非线性相位噪声追踪算法

在相干光纤通信系统中,为了提高接收端的相位追踪算法性能,提出了一种相位追踪算法——基于改进的判决导向递归最小二乘(DD-RLS)算法,将改进的DD-RLS算法和非线性前补算法结合应用于WDM相干光纤系统中抑制交叉相位调制(XPM)。传输仿真结果表明:该算法能够有效抑制系统中的XPM效应,在1000 km的11个信道的波分复用(WDM)系统传输中,相比传统DD-RLS算法,该算法能够更好地追踪相干WDM系统中的非线性相位噪声,信号Q~2值提高了0.8 dB。     

NOLM全光波长变换输出脉冲波形特性研究

本文分析了在利用非线性光学环形镜的开关效应和光纤内交叉相位调制效应实现全光波长变换系统中,色散位移光纤长度、砂浦脉冲峰值功率、泵浦脉冲宽度以及泵浦脉冲和连续探测波之间群速度失配参量对输出脉冲波形特性的影响。通过优化系统各项参数,可以在实现最高转换效率的同时,降低波长变换脉冲扶真程度,使波长变换脉冲无展宽,从而适用于超高速率通信系统。     

Multicanonical Monte Carlo Modeling of Wavelength Division Multiplexed Differential Phase Shift Keying Systems

Differential phase shift keying (DPSK) modulation is being considered as a possible candidate for future optical wavelength division multiplexed (WDM) transmission systems. In a single channel link, the balanced interferometric DPSK receiver exhibits increased tolerance against amplified spontaneous emitting (ASE) noise and fiber nonlinear effects. In this paper, a model is presented that can be used to estimate the performance of a multichannel DPSK system taking into account the influence of interchannel phenomena, namely cross-phase modulation (XPM) and four wave mixing (FWM), in the phase noise statistics. The model is based on an approximate solution of the fiber propagation equation and the multicanonical Monte Carlo (MCMC) method. It provides an efficient tool that can be used to investigate the influence of many link design parameters such as channel spacing, launch power, and fiber dispersion. The model is illustrated in the comparison of the performance of multichannel DPSK to on-off keying (OOK) systems. It is verified that, even in the presence of interchannel effects, DPSK modulation greatly enhances the system performance compared to OOK.     

Self-Pumping Wavelength Conversion for DPSK Signals and DQPSK Generation Through Four-Wave Mixing in Highly Nonlinear Optical Fiber

A novel scheme is proposed to achieve self-pumping wavelength conversion for two differential phase-shift keying (DPSK) signals at different wavelengths through four-wave mixing (FWM) effect in a highly nonlinear optical fiber. By changing the phase modulation depths to pi/2 for both of the DPSK signals, the two signals can be multiplexed to generate a differential quadrature phase-shift keying signal. The simulations and experimental results demonstrate the feasibility of phase manipulations for phase-shift keying signals through the FWM process     

RZ-DPSK传输系统相位噪声的比较分析

建立了单信道40Gbit／s归零-差分相移键控码（RZ-DPSK）传输系统模型，详细地分析并比较了线性相位噪声和非线性相位噪声对系统性能的影响。结果表明，由放大器自发辐射（ASE）噪声带来的线性相位噪声对传输系统的性能影响最大，ASE与自相位调制（SPM）相互作用引起的Gordon-Mollenauer（G-M）相移次之，带内四波混频（IFWM）的影响最小。在最优输入功率的条件下，由ASE带来的线性相位噪声引起的系统差分相位Q值代价大于204dB，由G-M相移引起的系统差分相位Q值代价小于7．5dB。仿真结果表明，对于采用掺铒光纤放大器（EDFA）级联放大的单信道40Gbit／s RZ-DPSK传输系统，ASE噪声是限制系统无中继传输距离的最主要因素。     

补偿色散和非线性相位噪声的新型光谱反演器

设计了一种新型光谱反演器,并演示了该器件在光纤传输系统中对于色散和非线性相位噪声的补偿作用。该补偿作用可以使得光纤传输系统的有效传输距离得到显著的提高,对于未来光传输系统的发展有着重大的作用。     

缓冲器输出端相位噪声模型分析

相位噪声是振荡器的重要性能指标。近年来,研究人员在振荡器相位噪声表征方面已经做了大量的工作,在这些过程中开发出了很多不同类型的振荡器相位噪声模型。但是在这些模型中,都没有分析缓冲器噪声对振荡器相位噪声的影响。而在研究课题中,首先要对缓冲器噪声的功率谱密度函数进行数学建模,并易于将这个模型嵌入到相位噪声的非线性扰动分析模型,这样就得到了含有缓冲器噪声的振荡器相位噪声模型。     

Experimental Demonstrations of All-Optical Phase-Multiplexing Using FWM-Based Phase Interleaving in Silica and Bismuth-Oxide HNLFs

We propose an all-optical phase-interleaving technology based on dual-pump four-wave mixing (FWM) in highly nonlinear fiber (HNLF). The proposed all-optical phase-interleaving technology is applied in an all-optical phase-multiplexing scheme to successfully phase-multiplex 2x or 3$,times,$10-Gb/s DPSK-WDM signals to a 20- or 30-Gb/s DPSK in non-return-to-zero (NRZ) formats. The proposed all-optical phase multiplexing scheme is demonstrated using dual-pump FWM in highly nonlinear silica and bismuth fibers. In contrast with optical time-division multiplexing technology, the proposed all-optical phase-multiplexing technology does not require pulse-carving, thus offering a high spectral-efficiency. Differential precoder for each input tributary is operated independently, and no additional encoder or postcoder is required to recover the original data after demodulation on the receiver side.      

光纤CATV中调相法抑制相位干涉噪声的研究

本文从理论上研究了附加相位调制抑制相位干涉噪声的方法 ,研究表明 :在光纤AM CATV外调制传输系统中 ,对传输光载波信号引入附加相位调制 ,当相位调制信号的频率为CATV频带的两倍以上时 ,可以有效地抑制相位干涉噪声的发生 ,抑制程度与相位调制度有关。     

基于随机非线性微分方程的振荡器相位噪声研究

根据振荡器电路的时变非线性特性 ,运用一种通用的相位噪声理论 ,通过对噪声源随机过程建模 ,求解具有严格数学意义的随机非线性微分方程 ,得到一个常数 c来描述时间抖动和频谱扩散。分别用基于随机非线性微分方程和线性时变的方法求解 ,结果表明线性时变得到的相位噪声频谱在基频附近分布的能量之和超过载波能量 ,在物理意义上有一定不足 ;而文中的相位噪声分析结果表明相位噪声只改变能量的分布并不能使能量显著增加 ,得到的结果为设计电路时减少相位噪声影响提供了思路。     

Performance improvement of phase-shift-keying signal transmission by means of optical limiters using four-wave mixing in fibers

Improvement of transmission performance of phase-shift-keying signals by the use of ultrafast optical limiters (amplitude regenerators) based on four-wave mixing (FWM) in fibers is theoretically and numerically studied. Theoretical analysis focuses on the nonlinear phase noise (the Gordon-Mollenauer effect) and its reduction by the limiters. It is shown that the cubic growth of the phase variance as the distance extends can be suppressed by the limiters that are periodically inserted in the system, although some additional phase noise is introduced by them. Numerical simulation is performed for nonreturn-to-zero (NRZ) differential phase-shift-keying (DPSK) transmission in a quasi-linear highly dispersed-pulse system with and without limiters. The results show that the maximum transmission distance is extended by the limiters. A clear indication of nonlinear phase-noise reduction at the high-signal-power regime, however, is not seen. This is attributed to the existence of intrachannel-FWM-induced phase fluctuation, which cannot be effectively suppressed by the amplitude limiter.