检索结果-南通市图书馆

Weakly-coupled mode division multiplexing over conventional multi-mode fiber with intensity modulation and direct detection

在线全文

学校读者我要写书评

暂无评论

Frontiers of Optoelectronics 2019年第1期12卷 31-40页

作者： Juhao LI Zhongying WU Dawei GE Jinglong ZHU Yu TIAN Yichi ZHANG Jinyi YU Zhengbin LI Zhangyuan CHEN Yongqi HE State Key Laboratory of Advanced Optical Communication Systems and Networks Peking UniversityBeijing 100871China Wuhan Research Institute of Posts and Telecommunications Wuhan 430074China

Multi-mode fiber(MMF)links are expected to greatly enhance capacity to cope with rapidly increasing data traffic in optical short-reach systems and networks.Recently,mode division multiplexing(MDM)over MMF has been proposed,in which different modes in MMF are utilized as spatial channels for data transmission.Stronglycoupled MDM techniques utilizing coherent detection and multiplex-input-multiplex-output(MIMO)digital signal processing(DSP)are complex and expensive for shortreach transmission.So the weakly-coupled approach by significantly suppressing mode coupling in the fiber and optical components has been proposed.In this way,the signals in each mode can be independently transmitted and received using conventional intensity modulation and direct detection(IM-DD).In this paper,we elaborate the key technologies to realize weakly-coupled MDM transmission over conventional MMF,including mode characteristic in MMF and weakly-coupled mode multiplexer/ demultiplexer(MUX/DEMUX).We also present the upto-date experimental results for weakly-coupled MDM transmission over conventional OM3 MMF.We show that weakly-coupled MDM scheme is promising for high-speed optical interconnections and bandwidth upgrade of already-deployed MMF links.

关键词： multi-mode fiber (MMF) mode division multiplexing (MDM) weak mode coupling intensity modulation and direct detection (IM-DD)

Numerical simulation of modulation to incident laser by submicron to micron surface contaminants on fused silica

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Physics B 2016年第1期25卷 632-639页

作者：杨亮向霞苗心向李莉袁晓东晏中华周国瑞吕海兵郑万国祖小涛 School of Physical Electronics University of Electronic Science and Technology of ChinaChengdu 610054China Research Center of Laser Fusion China Academy of Engineering PhysicsMianyang 621900China

modulation caused by surface/subsurface contaminants is one of the important factors for laser-induced damage of fused silica. In this work, a three-dimensional finite-difference time-domain （3D-FDTD） method is employed to simulate the electric field intensity distribution in the vicinity of particulate contaminants on fused silica surface. The simulated results reveal that the contaminant on both the input and output surfaces plays an important role in the electric field mod- ulation of the incident laser. The influences of the shape, size, embedded depth, dielectric constant （er）, and the number of contaminant particles on the electric field distribution are discussed in detail. Meanwhile, the corresponding physical mechanism is analyzed theoretically.

关键词： fused silica laser-induced damage particulate contaminants modulation

100-Gb/s undersea transmission with high spectral efficiency using pre-filtered QPSK modulation format

在线全文

学校读者我要写书评

暂无评论

Chinese Optics Letters 2010年第9期8卷 831-836页

作者： J.-X. Cai Y. Cai C. R. Davidson D. G. Foursa A. Lucero O. Sinkin W. Patterson A. Pilipetskii G. Mohs Neal S. Bergano Tyco Electronics Subsea Communications LLC ("TE SubCom" formerly known as ~co Telecommunications (US) Inc.) 250 Industrial Way West Eatontown NJ 07724 USA

We provide a review of our recent 100-Gb/s, high spectral efficiency （SE） experiment targeting transoceanic and regional undersea transmission distances. We demonstrated that simple pre-filtering at the transmitter together with a maximum a posteriori probability （MAP） detection algorithm can significantly improve SE. We transmitted 96×100-Gb/s pre-filtered polarization division multiplexed return-to-zero quadrature phase shift keyed （PDM-RZ-QPSK） channels with 300% SE over 10608 km using 52-km spans of 150-μm 2 fiber and simple single-stage erbium-doped fiber amplifiers （EDFAs）. We also achieved 400% SE over 4368 km using similar techniques.

关键词： Bit error rate Erbium doped fiber amplifiers modulation Optical signals Quadrature phase shift keying Signal processing

Maximal capacity nonorthogonal pulse shape modulation

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2015年第6期28卷 1699-1708页

作者： Chen Zhaonan Wang Hongxing Liu Xiguo Zhong Peilin Department of Electrical and Information Engineering Naval Aeronautical and Astronautical University Department of Basic Experiment Naval Aeronautical and Astronautical University

To improve spectral utilization of communication system, a novel nonorthogonal pulse shape modulation （NPSM） based on prolate spheroidal wave function （PSWF） is proposed. The modulation employs nonorthogonal PSWF pulses to transmit information and it shows a higher capacity than traditional orthogonal modulations. The NPSM capacity under the constraint of finite input alphabet, which is determined by parameters of PSWF pulse, is derived. An optimiza- tion model for maximal capacity of NPSM is constructed and an exhaustive self-adapting gradient search algorithm for the model is proposed. A practical NPSM scheme with the maximal capacity is obtained by this search algorithm and it is proved to be superior to orthogonal signaling in the capacity. Our theoretical analysis is validated by numerical simulations and practical tests, and the results show that NPSM outperforms orthogonal modulations in the capacity and has a lower Peak-to-Average Power Ratio.

关键词： capacity modulation Orthogonality Prolate spheroidal wave function Quadrature amplitude modulation

Effect of wall temperature modulation on the heat transfer characteristics of droplet-train flow inside a rectangular microchannel

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Engineering 2020年第3期28卷 685-697页

作者： Vivekanand S.V.B.,Raju V.R.K. Department of Mechanical Engineering National Institute of TechnologyWarangalTelangana 506004India

The numerical studies of water–oil two-phase slug flow inside a two-dimensional vertical microchannel subjected to modulated wall temperature boundary conditions have been discussed in the present paper.Many researchers have contributed their efforts in exploring the characteristics of Taylor flows inside microchannel under constant wall heat flux or isothermal wall conditions.However,there is no study available in the literature which discusses the impact of modulated thermal wall boundary conditions on the heat transfer behavior of slug flows inside microchannels.Hence,to bridge this gap,an effort has been made to understand the heat transfer characteristics of the flow under sinusoidal wall temperature conditions.Initially,a single phase flow and heat transfer study was performed in microchannels,and the results of the fully developed velocity profile and heat transfer rate were validated with benchmark analytical results.Then an optimal selection of the combination of sinusoidal thermal wall boundary conditions has been made for the two-phase slug flow study.Later,the effects of amplitude(0 bεb 0.03)and frequency(0 bωb 750πrad·s-1)of the sinusoidal wall temperature profile on the heat transfer have been studied using the optimal combination of the wall boundary conditions.The results of the numerical study using modulated temperature conditions on channel walls showed a significant improvement in the heat transfer over liquid-only flow by approximately 50%as well as over two-phase flow without wall temperature modulation.The non-dimensional temperature contours obtained for different cases of temperature modulation clearly explain the root cause of such improvement in the heat transfer.Besides,the results based on the hydrodynamics of the flow have also been reported in terms of variation of droplet shapes and film thickness.The influence of Capillary number on the film thickness as well as heat transfer rates has also been discussed.In addition,the measured film thickness has also been compared with that cal

关键词： Heat transfer Microchannel modulation Surface tension Taylor flow

Ultrasensitive polarization-dependent terahertz modulation in hybrid perovskites plasmoninduced transparency devices

在线全文

学校读者我要写书评

暂无评论

Photonics Research 2019年第9期7卷 994-1002页

作者： JUNHU ZHOU YUZE HU TIAN JIANG HAO OUYANG HAN LI YIZHEN SUI HAO HAO JIE YOU XIN ZHENG ZHONGJIE XU XIANG’AI CHENG College of Advanced Interdisciplinary Studies National University of Defense TechnologyChangsha410073China State Key Laboratory of High Performance Computing College of ComputerNational University of Defense TechnologyChangsha410073China National Innovation Institute of Defense Technology Academy of Military Sciences PLA ChinaBeijing100071China

Active control of metamaterial properties with high tunability of both resonant intensity and frequency is essential for advanced terahertz(THz) applications, ranging from spectroscopy and sensing to communications.Among varied metamaterials, plasmon-induced transparency(PIT) has enabled active control with giant sensitivity by embedding semiconducting materials. However, there is still a stringent challenge to achieve dynamic responses in both intensity and frequency modulation. Here, an anisotropic THz active metamaterial device with an ultrasensitive modulation feature is proposed and experimentally studied. A radiative-radiative-coupled PIT system is established, with a frequency shift of 0.26 THz in its sharp transparent windows by polarization rotation. Enabled by high charge-carrier mobility and longer diffusion lengths, we utilize a straightforwardly spincoated MAPbI3 film acting as a photoactive medium to endow the device with high sensitivity and ultrafast speed.When the device is pumped by an ultralow laser fluence, the PIT transmission windows at 0.86 and 1.12 THz demonstrate a significant reduction for two polarizations, respectively, with a full recovery time of 561 ps. In addition, we numerically prove the validity that the investigated resonator structure is sensitive to the optically induced conductivity. The hybrid system not only achieves resonant intensity and frequency modulations simultaneously, but also preserves the all-optical-induced switching merits with high sensitivity and speed, which enriches multifunctional subwavelength metamaterial devices at THz frequencies.

关键词： THz Ultrasensitive polarization-dependent terahertz modulation in hybrid perovskites plasmoninduced transparency devices

Soliton excitation in the pass band of the transmission line based on modulation

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2016年第4期25卷 115-120页

作者：赵帼英陶锋陈伟中 School of Computer Science and Technology Anhui University of Technology Ma' anshan 243002 China School of Electrical and Information Engineering Anhui University of Technology Ma' anshan 243002 China Key Laboratory of Modern Acoustics Ministry of Education and Institution of Acoustics Nanjing University Nanjing 210093 China

We numerically investigate the excitation of soliton waves in the nonlinear electrical transmission line formed by many cells. When the periodic driving voltage with frequency in the pass band closing to the cutoff frequency is applied to the endpoint of the whole line, the soliton wave can be generated. The numerical results show that the soliton wave generation mainly depends on the self modulation associated with the nonlinear effect. In this study, the lower subharmonic component is also observed in the frequency spectrum. To further understand this phenomenon, we study the dependence of the subharmonic power spectrum and frequency on the forcing amplitude and frequency numerically, and find that the subharmonic frequency increases with the gradual growth of the driving amplitude.

关键词： soliton nonlinear transmission line modulation

Effects of variable viscosity and temperature modulation on linear Rayleigh-Bénard convection in Newtonian dielectric liquid

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics and Mechanics(English Edition) 2019年第11期40卷 1601-1614页

作者： P.G.SIDDHESHWAR D.UMA S.BHAVYA Department of Mathematics Bangalore UniversityBengaluru 560056India Department of Computer Science and Engineering PES UniversityBengaluru 560085India Department of Mathematics Atria Institute of TechnologyBengaluru 560024India

The linear Rayleigh-Bénard electro-convective stability of the Newtonian dielectric liquid is determined theoretically subject to the temperature modulation with time.A perturbation method is used to compute the critical Rayleigh number and the wave number.The critical Rayleigh number is calculated as a function of the frequency of modulation,the temperature-dependent variable viscosity,the electric field dependent variable viscosity,the Prandtl number,and the electric Rayleigh number.The effects of all three cases of modulations are established to delay or advance the onset of the convection process.In addition,how the effect of variable viscosity controls the onset of convection is studied.

关键词： dielectric liquid temperature dependent variable viscosity electric field dependent variable viscosity electric Rayleigh number temperature modulation

A jamming method against bistatic SAR based on modulation theory

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Engineering and Electronics 2019年第3期30卷 504-510页

作者： RAN Jinhe LI Xiuhe SHEN Yang Electronic Countermeasure Institute National University of Defense Technology

This paper focuses on the jamming problem of bistatic synthetic aperture radar (BiSAR), and a jamming method against BiSAR based on modulation theory is proposed. The proposed jamming method modulates the BiSAR signal with the cosinusoidal phase to generate multi-false targets in range, and further rotates the jammer to generate multi-false targets in azimuth. The range multi-false targets and azimuth multi-false targets form the two-dimensional cover jamming or deception jamming, which can protect the important targets efficiently. The number of false targets, the interval of false targets, and the jamming square can be adjusted flexibly by setting different range jamming parameters and azimuth jamming parameters. The jamming performance and the choosing criteria of jamming parameters are also discussed. Finally, the simulated data verify the effectiveness of the jamming method.

关键词： bistatic synthetic aperture radar (BiSAR) cosinusoidal phase cover jamming micro-motion modulation