一种基于幅度统计矩的MQAM信号分类方法

针对加性高斯白噪声(AWGN)环境下M进制正交幅度调制(MQAM)信号的调制分类,提出了一种基于幅度统计矩的MQAM信号分类法,推导出了用于区分MQAM信号的特征参数表达式。计算机仿真结果与理论分析一致,仿真结果表明,在信噪比不低于5 dB时,该方法的正确识别率可保持在97%以上,证明了该方法的有效性。     

灵活高阶正交幅度调制矢量光信号的产生与传输分析

灵活光发射机可根据不同应用场景需求软定义信号的调制格式,从而进一步优化光信号的传输性能。本文提出了一种基于双平行马赫-曾德尔调制器（MZM）和单MZM级联的灵活高阶正交幅度调制（QAM）光发射机方案,理论分析了圆形16QAM、4幅4相16QAM、圆形32QAM以及4幅8相32QAM光信号产生与自适应切换的原理与方法。在虚路径标识符（VPI）仿真环境下,分别验证了上述4种信号在5 Gbaud和10 Gbaud调制速率下的产生和传输性能。结果表明,通过灵活配置发射机的驱动信号（二进制或四进制）与直流偏置电压,可实现8/16/32QAM信号间的自由切换,同时,生成的上述4种信号经一定长度单模光纤传输后具有良好的信噪比。     

光DQPSK调制在不同色散补偿系统中的性能

分析了光非归零-差分正交相移键控(NRZ-DQPSK)、33%归零-差分正交相移键控(33%RZ-DQPSK)和载波抑制归零-差分正交相移键控(CSRZ-DQPSK)三种调制格式的频域特性。并数字仿真了40Gbit/s的单信道光纤系统中三种调制格式在对色散(CD)进行后补偿、预补偿和对称补偿等三种补偿方式及考虑偏振模色散(PMD)和非线性效应情况下的传输性能。仿真结果表明,33%RZ-DQPSK对自相位调制(SPM)有最好的容忍度,但缓解PMD和CD的能力较弱;CSRZ-DQPSK在色散后补偿方式中对PMD和非线性效应具有最好的抑制能力。     

高速光通信偏振模色散补偿前馈信号提取方法

为了得到高阶偏振模色散的前馈信息,采用数值模拟的方法,通过一种实时提取1阶和2阶偏振模色散的模型,直接得到了偏振模色散的大小和方向。将模拟得到的偏振模色散大小与从琼斯矩阵理论中计算的结果进行比较,结果表明,采用该模型的模拟结果与理论计算值在差分群时延为一个比特周期内符合较好。从得到的偏振模色散矢量的大小和方向信息可以为高阶偏振模色散补偿提供前馈信息。这一结果对偏振模色散的前馈补偿系统的设计具有参考价值。     

一种高速光纤通信高阶偏振模色散补偿的前馈信号提取方法

建立了一种实时提取一阶和二阶偏振模色散的模型,可以直接得到偏振模色散的大小和方向。通过数值模拟将得到的偏振模色散大小与从琼斯矩阵理论中计算的结果进行比较,我们模拟结果与理论计算值在差分群时延为一个比特周期内较好相符。从得到的偏振模色散矢量的大小和方向信息可以为高阶阶偏振模色散补偿提供前馈信息     

WDM系统中同步幅度调制技术对PMD的抑制

引入了随机扰动双折射单模光纤模型,导出了双波长的光波在随机双折射光纤中的非线性脉冲传输方程;在此基础上,研究了偏振模色散对2×10Gb／sWDM系统中脉冲序列传输的影响,并采用同步幅度调制控制技术有效地降低了偏振模色散的影响。     

色散和非线性对异步光码分多址系统的影响

为了研究色散和非线性对异步光码分多址系统性能的影响,基于非线性薛定谔方程,采用数值模拟的方法,取得了异步光码分多址系统误比特率与传输距离的关系曲线和与用户数关系曲线.结果表明,光纤中的群速度色散、3阶色散和非线性效应都会引起异步光码分多址系统性能劣化,其中以群速度色散效应的影响最为严重;系统传输媒质可以采用色散位移光纤...     

一种重要抽样仿真方法的研究及应用

介绍了蒙特-卡洛仿真原理,分析了改进型的蒙特-卡洛仿真即重要抽样(IS)的原理及其在通信中的应用,特别是在高速光纤通信的偏振模色散(PMD)仿真中的应用价值.实验证明,采用重要抽样的仿真方法可以得到大差分群时延(DGD)值的小概率事件,并且系统配置比用蒙特-卡洛的仿真方法简单得多.     

基于色散器件的光真延时线中的色散限制

利用强度-频率混合调制模型研究了基于色散器件的光真延时线中色散导致的延时误差的变化规律.基于对延时误差的分析,研究了色散对系统性能的限制,为光真延时线的设计提供了理论参考.     

改进的16进制正交幅度调制码的相位估计算法

相干光通信系统中的相位恢复是克服信号收发端和传输过程中产生的相位噪声的必要步骤。为获得低的运算复杂度和良好的相位估计效果,本文对传统的四次方相位估计算法进行了改进,使之具有自适应的数据块长度控制功能。通过理论分析以及Matlab数值仿真方法验证改进的效果。对于16进制正交幅度调制码（16QAM）,改进后的算法在几乎不增...     

光纤色散测量概述

介绍了三种最为成熟的光纤色散测量方法:时延法、相移法和干涉法,并从色散测量原理、测量装置、适用范围以及优缺点等几方面进行了论述.时延法测量精度不高,目前较少采用;相移法测量精度高,但测量仪器价格昂贵,测量成本高;干涉法既能满足一定的测量精度要求(时间分辨率可达1ps),又控制了测量成本,是普遍采用的测量方法.     

Chromatic dispersion monitoring technique using optical asynchronous sampling and double sideband filtering

This paper introduces a new chromatic dispersion monitoring technique using optical asynchronous sampling and double sideband filtering. We present simulation results that relate chromatic dispersion with the ratio between the maximum amplitude of the signal and the average optical output power, yielding in a method which is power transparent. We also show theoretical investigation and theoretical results that prove the approach used in this paper.     

Chromatic dispersion allocable compensator for optical fibre communications systems

In this work we perform a study about the temperature implications on the optical fibers chromatic dispersion and the implications on the quality of transported information. To solve this constrain we suggest two approaches to dynamically compensate chromatic dispersion, one based on chirped fiber Bragg gratings and other based on dispersion compensation fibers. With the dispersion compensation fibers, we obtain a first and second order tuning coefficients of 3.472 ps nm-1 ºC-1 and -2.7 × 10 -3 ps nm-2 ºC-1, respectively. With the compensator based on chirped fiber Bragg gratings we obtain dispersion values between -113.2 ps nm-1 and 143.1 ps nm-1, for temperature gradients of 40ºC.     

Chromatic dispersion measurement by white-light interferometry on metre-length single-mode optical fibres

Chromatic dispersion near 0.8 ?m in a short (~1 m) single-mode optical fibre is determined by a white-light interferometric technique. In particular, the wavelength-dependent group delay of the fibre is obtained directly from the spectra of the output light from a Mach-Zehnder interferometer illuminated by a GaAlAs LED. Its application in single-mode fibre studies in the 1.3 ?m wavelength region is discussed.     

Chromatic dispersion modeling of single-mode optical fibers: adetailed analysis

We present here an efficient method for single-mode fiber modeling. This paper deals mainly with chromatic dispersion computation but the analysis can be extended to other single-mode characteristics. This synthesis shows that key-parameters have to be correctly chosen in order to insure an accurate modeling of chromatic dispersion. Finally, the results we obtained with this method are presented. The agreement between theoretical calculations and measurements is also explained     

Chromatic dispersion measurement of optical components usinglightwave synthesized frequency sweeper

We propose a chromatic dispersion (CD) measurement method that uses a lightwave synthesized frequency sweeper (LSFS), which generates a frequency swept output with very good linearity. With the LSFS, we can measure the CD of optical components in a very short time. Moreover, the employment of a lock-in detection with phase diversity technique makes it possible to fully utilize the good wavelength resolution and accuracy of the LSFS. We describe the principle of the method and analyze the noises that are intrinsic to it. We also report an experimental result that confirmed the method's feasibility     

An chromatic dispersion monitoring method based on spectral-shift of SOA

A remnant dispersion monitoring method based on spectral-shift of SOA in high speed optical communication system with CSRZ format and single channel speed of 40 Gbit/s is proposed. The system performance can be optimized by careful choosing bandwidth and center wavelength of the optical fiber grating filter. The dynamical monitoring range is ±60 ps/nm and the monitoring precision is about 5 ps/nm. This method can be suitable for the application in dynamical dispersion compensation of high speed optical communication systems.     

Improved all optical chromatic dispersion monitoring method for WDM systems

In this paper we propose an improved all optical chromatic dispersion (CD) monitoring method applicable to wavelength division multiplexing (WDM) systems with intensity or phase modulation format. This method can operate over a much larger bandwidth and CD monitoring range and is insensitive to optical signal-to-noise ratio (OSNR) and polarization mode dispersion (PMD). These improvements are achieved by utilizing a wavelength tunable laser as the probe to maintain the appropriate phase-matching condition and a loop-back controlled tunable CD compensator to discriminate CD distortions from PMD and OSNR influences. Numerical simulations show that by this method the operational bandwidth and CD monitoring range can be expanded to cover C + L bands and ±1600 ps/nm, respectively, for different modulation formats and the sensitivity is higher than the other methods proposed before.     

Chromatic dispersion dependence of asynchronous amplitude histogram evaluation of NRZ signal

This paper presents the chromatic dispersion dependence of the averaged Q-factor method based on an evaluation of an asynchronous amplitude histogram. We analyze nonreturn-to-zero optical signals using a numerical simulation based on several parameters for signal quality monitoring. The results are compared with the optical signal-to-noise ratio dependence of the method and the possibility of distinguishing the origins of the bit-error-rate distortion is discussed.