基于混合调制的WDM-RoF-PON系统仿真研究

在介绍光载无线系统原理的基础上,设计了基于混合调制WDM-RoF-PON系统架构,采用仿真软件来搭建系统验证该混合调制系统结构的合理性;并提出了一种混合调制方案,在下行数据流中采用IRZ码型,具有更好的消光比和色散容限,降低了用户接收端设备成本,提高了系统传输质量.仿真实验表明混合调制WDM-RoF-PON网络架构方案合理且具有一定的实用价值.     

通过恒包络调制提高相干光OFDM系统的光纤非线性容限

相干光正交频分复用(CO-OFDM)对光纤链路中 的色度色散(CD)和偏振模色散(PMD)具有较强的容忍性,但 是OFDM信号高峰均功率比(PAPR)的特点使其对光纤非线性效应 非常敏感,严重影响了系统传输性能。 本文提出了基于恒包络(CE)调制的方法使得系统中光信号PAPR降低为0dB,从而提高了CO-OFDM系统的非 线性传输性能。仿真结果表明,子载波采用16QAM调制的40Gbit/s单信道CE调制CO -OFDM系统,在经800km无色散补偿、欠色散补偿和周期全色散补偿 标准单模光纤(SSMF)链 路传输后,虽然较传统CO-OFDM存在约1.8dB的代价,但是系统最大 发射光功率分别提高 了6.2、9.3dB。并且,将本文方案应 用 到CO-OFDM和10Gbit/s NRZ-OOK混合传输WDM系统中,信道最大发 射光功率仍获得了5.2dB的提高。因此,本文提出的CE调制方法能有 效地提高CO-OFDM系统在不同传输环境中的光纤非线性容限。     

40Gb/s光DQPSK传输系统性能分析

介绍了光差分正交相移键控(DQPSK)的调制和解调方式,对非归零码(NRZ),归零码(RZ)和载波抑制归零码(CSRZ)进行调制,研究40Gb/s高速传输系统中不同类型的光信号.使用色散补偿方式进行200km的模拟仿真,比较不同码型的传输特性.分析表明CS-RZ-DQPSK调制格式,具有更强的抗色散和偏振模色散能力,在较宽的入纤功率范围内取得最小的眼图张开代价.     

16×40Gbit/s DWDM系统色散补偿和调制方式研究

对传输容量为16×40Gbit/s、传输距离为500～2 000km的DWDM(密集波分复用)系统进行了研究。分析了不同调制方式(CSRZ(载波抑制归零)码、DRZ(双二进制归零)码和MDRZ(改进的双二进制归零)码)、不同色散补偿方案(前置、后置和中间色散补偿)对系统传输性能的影响。仿真结果表明,当传输距离超过1 500km后,MDRZ码能够很好地抑制FWM(四波混频)效应,提高系统性能;中间色散补偿方案比前置色散补偿和后置色散补偿有更好的补偿效果。     

光纤传输系统中基于相位预调制的信号整型

利用相位预调制技术解决高速长距离光纤传输系统中面临的接收灵敏度降低和色散容限问题。通过在发射端对非归零(NRZ)的光信号进行比特同步相位预调制,使非归零码在传输过程中得到波形重整,演变为归零(RZ)的波形,从而提高眼图开启度。实验观测了普通非归零码和相位预调制的非归零码在不同相位调制深度和色散下的光谱、眼图和功率代价。10Gb/s的传输结果表明,链路色散绝对值小于1000ps/nm时,施加相位预调制的非归零信号功率代价小于1dB,比普通非归零信号具有更高的接收灵敏度和更低的色散功率代价。因此,基于相位预调制的信号整型技术可减轻系统对光信噪比和色散管理的要求,延长传输距离。     

数字电视传输中的关键技术（第六讲）M-QAM调制

数字电视调制可分两大类：数字电视下行(正向)传输采用的调制和数字电视上行(反向)传输采用的调制。不同的传输方式采用的调制方式不同。正向传输指的是从前端向用户端传输。反向传输指的是用户端向前端传输。在双向传输网络中才有反向传输。此处仅介绍下行M-QAM数字调制技术。     

基于窄带光纤光栅的微波载波单边带调制

利用窄带光纤光栅简单而有效地实现了RoF系统中单边带调制,克服长距离传输时的色散损耗.分析了RoF系统中双边带调制对系统带来的影响,以及单边带滤波对窄带光纤光栅反射光谱和反射率的要求.研究了采用基于窄带光纤光栅的单边带调制后,对不同调制方式、不同调制速率、不同传输距离的RoF传输系统性能的改善情况.实验研究表明,光纤光栅单边带调制在以16QAM调制的15GHz RoF系统中传输25km后,信噪比与双边带调制相比可提高约4dB.     

毫米波RoF光通信系统中外调制技术的研究

从理论和仿真两个角度分析了毫米波的两种光外调制生成方式DSB和SSB.通过眼图分析表明,受光纤色散的影响,DSB调制方式导致毫米波信号功率随传输距离的增大呈现周期性衰减,不适于长距离传输.SSB调制方式能够有效的抑制色散导致的毫米波功率损耗,适于长距离传输.最后针对采用SSB方式传输的不足之处提出了相应的改进方案.     

光纤通信系统中的非线性数字补偿调制研究

为了分析不同调制方式下的光纤通信系统非线性数字补偿效果,文中以具有标准单模光纤(SSMF)传输链路的间隔波分复用(WDM)光纤通信系统为基础,通过建立信号之间、信号与噪声之间相互作用引起的非线性失真数学模型,利用互信息(MI)与可达信息速率(AIR)作为多信道数字反向传播(MC-DBP)计算复杂度指标,研究了理想Nyquist间隔光纤通信系统中调制方式与MC-DBP性能的关系。实验结果表明,最大信道DBP系统的非线性失真与调制方式无关,而电子色散补偿(EDC)和部分信道DBP的非线性失真取决于调制方式。     

调制格式对再调制WDM-PON系统性能的影响

比较和分析了使用1.25Gb/s,2.5Gb/s and 5Gb/s的曼彻斯特编码和NRZ编码下行信号,1.25Gb/s NRZ编码上行信号的基于反射式半导体光放大器(RSOA)的波长重用波分复用无源光网络(WDM-PON)系统的性能.实验结果表明,相对于NRZ调制格式,曼彻斯特编码可获得更好的功率余量,尤其是在上下行信号速率非对称的网络中,曼彻斯特编码具有更加明显的优越性.     

Noncoherent-coded modulation constructed from conventionaltrellis-coded modulation

We propose a method to construct noncoherent-coded modulation (NCM) by modifying the conventional trellis-coded modulation (TCM) as proposed by Ungerboeck (1982). The error performance of the modified TCM using noncoherent decoding can approach that of the conventional TCM using coherent decoding for additive white Gaussian noise     

交叉相位调制不稳定性的进一步分析

从耦合非线性薛定谔方程出发,分析了光纤中两光波因交叉相位调制(XPM)所致的调制不稳定性(MI)产生的条件及增益谱。结果表明,当一光波处于正常群速度色散(GVD)区,另一光波处于反常群速度色散区时,与两光波参数有关的扰动增益谱应有3种可能的形式;在一定条件下,在某一微扰频率范围内,甚至还会同时出现两种形式的增益谱。     

The 'inverted' gain-levered semiconductor laser-direct modulation with enhanced frequency modulation and suppressed intensity modulation

A gain-levered semiconductor laser has enhanced efficiencies in both intensity modulation (IM) and frequency modulation (FM). It is shown that by inverting the bias points of the gain and modulation sections, a mode of operation referred to as 'inverted' gain-lever, the FM efficiency is suppressed. The large FM-to-FM ratio makes it a desirable source for an FM optical transmitter.<>     

时间调制阵列天线的非理想波形调制研究

针对时间调制阵列天线中射频开关的非理想特性,开展了多种波形调制下的谐波特性研究. 首先,推导了非对称梯形波/升余弦波周期调制的傅里叶系数,分析两种调制波的非对称性对各次谐波的幅度、相位和能量占比的影响;在此基础上,通过实验获得了一组实验调制波,并运用三角函数多项式拟合真实调制波形的上升沿与下降沿;最后,讨论了各种波调制与实测谐波分量的差异性. 结果表明,与已有调制波相比,本文所提出的非对称梯形波、非对称升余弦波和拟合波的调制更接近真实波调制.     

Permutation modulation

A class of codes and decoders is described for transmitting digital information by means of bandlimited signals in the presence of additive white Gaussiau noise. The system, called permutation modulation, has many desirable features. Each code word requires the same energy for transmission. The receiver, which is maximum likelihood, is algebraic in nature, relatively easy to instrument, and does not require local generation of the possible sent messages. The probability of incorrect decoding is the same for each sent message. Certain of the permutation modulation codes are more efficient (in a sense described precisely) than any other known digital modulation scheme. PCM, ppm, orthogonal and biorthogonal codes are included as special cases of permutation modulation.     

Delta modulation

The idea of coding the human voice into digital pulses was conceived more than three decades ago; exploitation had to await the ushering in of the transistor era. Since then, coding systems gradually have improved. One of the latest and most efficient schemes is delta modulation. Compared with earlier analog-to-digital-pulse conversion systems, an increase in the voice-handling capacity of telephone equipment by a factor of two or more has been made possible. At the same time, equipment requirements have become less stringent.     

Delay modulation

The definition of the encoding procedure known as delay modulation is given, along with the autocorrelation function and the spectral density. It is shown that the procedure generates a waveform for magnetic recording which is superior to presently used encoding processes.     

Multirate modulation: a bandwidth- and power-efficient modulation scheme

Multirate (MR) modulation resembles block-coded modulation (BCM), since matrices are being used to transform binary input vectors to multilevel output vectors (blocks) of length K. Unlike BCM, attention is given to the spectral shaping of the signal to be transmitted. Hence, the encoding matrices are designed to provide simultaneous spectral shaping and Euclidean distance. The encoding matrices can be implemented by using MR digital filters of low complexity. MR modulation also resembles partial response (PR) modulation since, in both cases, a transmitter and receiver filter is used with an overall duobinary impulse response. It will be shown that MR modulation has a number of significant advantages compared with PR modulation. Thus, for example, with MR modulation, loss of synchronization or gain control, as can occur with PR modulation, cannot happen in the receiver. Furthermore, computer simulations for an additive white Gaussian noise channel demonstrate that, for a bit-error rate of 10/sup -6/, MR modulation (with K=10) gives a gain of 1.5 dB, compared with PR modulation and symbol-by-symbol detection. However, MR modulation requires a slightly higher bandwidth. It is also explained how, for block lengths K/spl ges/10, MR modulation gives a larger bandwidth efficiency than M-ary pulse-amplitude modulation with raised-cosine pulses and a rolloff factor /spl alpha//spl ges/0.1.     

SBM 调制解调技术性能分析及仿真

SBM(序列平衡调制)以简单的实现方式,通过提取脉冲对的相位差来实现译码和测距,实现数据传输的同时达到测距的目的。对 SBM 的误码性能和测距性能进行分析,采用矢量相位比较技术提高测距精度,并进行了模拟各种测距误差来源和通过基于数学模型的测距精度仿真。     

Code modulation of m-sequences

A family of binary sequences exists with the property that the cross-correlation function of each member with a reference m-sequence has a unique pattern of four peaks with equal offsets from a constant base level. The positive peak is position invariant and knowledge of the locations of the remaining three peaks, which are negative, identifies the sequence. A simple method for generating the sequences is given and an application in the form of a system for data transmission by code modulation of an m-sequence carrier is proposed.