基于色散补偿光子晶体光纤的双通道光子时间拉伸模数转换器系统研究

研究了色散补偿光子晶体光纤(DC-PCF)对双通道光子时间拉伸模数转换器(PTS-ADC)的性能影响。通过理论推导验证了DC-PCF抑制PTS-ADC中三阶谐波产生的原理。设计了一种基于DC-PCF的双通道PTS-ADC系统,利用Optisystem软件对该系统进行仿真研究,分别对5组不同的输入射频(RF)信号(16.25,20.25,24.25,28.25,32.25GHz)进行模数转换,对比DC-PCF和色散补偿光纤(DCF)作为色散介质时系统的有效量化位数等性能参数。仿真结果表明,DC-PCF能够有效抑制三阶谐波的产生,提高双通道PTS-ADC的量化精度。     

光纤非线性效应对光子时间拉伸模数转换系统性能的影响

光子时间拉伸模数转换(PTS-ADC)系统利用光纤中的色散效应对被采样模拟信号进行时间拉伸和带宽压缩,可大幅提高电模数转换器(ADC)的采样率和带宽。现有的PTS-ADC系统需要很长的色散光纤作为传输介质,它所带来的损耗限制了系统信噪比(SNR)和有效比特位(ENOB)。虽可通过提高光脉冲功率来改善系统的SNR,但色散光纤中的非线性效应利用了信噪比的提升。从理论推导、数值仿真和实验验证三个方面综合分析了非线性效应对PTS-ADC系统性能的影响,包括系统功率传输函数、载波与谐波功率比(CIR)。结果表明:第一段色散光纤中的非线性效应不会使得被采样模拟信号失真,相反地会提高系统带宽和CIR;而第二段色散光纤中的非线性效应则会恶化系统性能,应予以避免。     

带宽为56.978 GHz光拍频信号实时测量

瞬态宽带宽光信号广泛存在于激光干涉测速、光通信等领域,具有宽带宽、非重复性的特点,但现有的直接或间接光脉冲测量技术还无法应用于此类信号的测量。利用时间-波长映射的啁啾光脉冲和四波混频效应对瞬态光信号进行超高速光采样,通过采用时间拉伸技术和色散介质,放大其时间尺度,成倍提高了后端电子记录系统的带宽及采样率。实验结果表明,该方法可以实时测量带宽为56.978GHz的光拍频信号,等效测量时间分辨率为3.7ps,证实了所提方法的有效性。     

一种不等带宽光学梳状滤波器

提出了一种新型—Michelson—三面镜FabryPerot型50GHz不等带宽光学梳状滤波器设计方案,分析和模拟表明:该器件将一路信道间隔为50GHz的输入信号分离成信道间隔为100GHz的奇偶两路输出信号,其中在3dB处,奇数信道带宽大于30GHz用于10Gb/s传输,偶数信道带宽大于60GHz用于40Gb/s传输对于将来的40Gb/s系统,该器件具有优势.     

混频技术测量单次脉冲微波频率的实验研究

 介绍了用混频技术测量单次脉冲微波频率的方法,用50ns、5GHz的单次脉冲微波对混频系统进行了实验研究。目前, 已用此技术测量了虚阴极振荡高功率微波锁频产生的单次微波的频率,并对混频输出的中频信号进行快速傅里叶变换(FFT),得到单次脉冲微波的3dB带宽。     

高频半导体激光器组件及其特性的研究

本文使用DC-PBH型激光二极管芯片,设计制作了实用化封装形式的激光器组件;在理论上和实验上研究了组件的封装模型和小信号频率调制特性,其光响应3dB带宽大于1.8GHz.该器件可满足六次群的光通信系统的带宽要求,也可用于GHz级的微波副载波光通信系统。     

武汉光电国家实验室成功实现目前世界最高Q值的微波光子学滤波器

本刊讯近年来，用光学方法处理微波和毫米波信号引起了广泛关注。相对于传统纯粹电学微波电路，微波光子学滤波器具有很多优点，比如低损耗、宽带宽、抗电磁干扰、可调谐以及重构性比较好等。它可以直接在光域里对微波或者毫米波信号进行处理，能够融合到光纤通讯系统和光学光纤网络中。     

基于量子压缩感知的宽带射频信号测量

随着雷达、电子战和5G通信等无线射频技术的快速发展,对宽带射频信号的测量和实时频谱表征变得越来越重要.传统射频信号实时测量技术受模数转换器采样率和数字信号处理能力的限制,存在测量带宽窄、数据量大、易受电磁干扰等问题.本文提出一种基于量子压缩感知的射频信号测量技术,使用集成电光晶体作为射频传感,通过被测射频信号调制光子波函数构建压缩感知机,实现对宽带射频信号的压缩测量,显著提升了频谱感知带宽.实验演示了工频和中频高压信号的长时间频谱监测,以及高频射频信号的实时频谱测量.在傅里叶极限频谱分辨率下,实现了GHz量级的实时频谱分析带宽,数据压缩率达到1.7×10^-5,可以满足5G无线通信、认知无线电等应用对宽带射频信号频谱测量的需求,为发展下一代宽带频谱感知技术提供了新的技术路径.     

光子集成射频自干扰消除系统性能仿真分析

针对全双工通信系统设计了光子集成射频自干扰消除功能芯片.该芯片采用相位调制将射频信号转换至光域,在光域内进行光载射频信号的幅相调控以实现干扰对消功能.对功能芯片中主要功能单元进行优化设计后,延时调谐范围为0～10ps,30GHz带宽内的延时抖动小于0.1ps;滤波响应阻带抑制度为36.5dB,通带带宽为60.6GHz,边沿陡峭度为9.2dB/GHz.建立了光子集成芯片射频自干扰消除系统的理论模型,对功能芯片中可调光延时线、可调光衰减器及滤波器等引入的延时、幅度不匹配对系统消除性能的影响进行了仿真分析.结果表明,幅度失配量为0.02dB时,2GHz带宽信号下系统抑制度为-42.7dB;延时抖动为0.07ps时,2GHz带宽信号下系统的抑制度为-37dB.研究结果可为光子集成射频干扰抑制功能芯片的研制提供参考.     

基于DFB激光器的光学微波信号的产生

采用量子阱混杂的材料集成技术制备并联分布反馈激光器和Y形波导耦合器集成的新型光电器件.两个并联分布反馈激光器的激射模式在频率上稍有差别,这两束不同频率的激光在Y形波导耦合器拍频产生光学微波信号.分别独立调节注入到两个激光器的电流大小,可以得到从13 GHz到42 GHz连续可调的光学微波信号. 关键词： 光学微波信号生成 分布反馈激光器 Y形波导 拍频     

Rigorous solution of a problem for a cylindrical cavity containing a ferrite and a dielectric

A rigorous solution is given for modes of TM_nmo type. The complex resonant frequency _n is expressed via a transcendental characteristic equation. Some particular cases are discussed.Read at the Third All-Union Conference on Ferrites, Leningrad, 23 October 1963.     

Towards a predictive scenario of a burning accident in a mining passage

To reveal the inner mechanisms of a combustion accident in a coalmine, the key stages and characteristics of premixed flame front evolution such as the flame shapes, propagation speeds, acceleration rates, run-up distances and flame-generated velocity profiles are scrutinised. The theories of globally spherical, expanding flames and of finger-flame acceleration are combined into a general analytical formulation. Two-dimensional and cylindrical mining passages are studied, with noticeably stronger acceleration found in the cylindrical geometry. The entire acceleration scenario may promote the total burning rate by up to two orders of magnitude, to a near-sonic value. Starting with gaseous combustion, the analysis is subsequently extended to gaseous-dusty environments. Specifically, combustible dust (e.g. coal), inert dust (e.g. sand), and their combination are considered, and the influence of the size and concentration of the dust particles is quantified. In particular, small particles influence flame propagation more than large ones, and flame acceleration increases with the concentration of a combustible dust, until the concentration attains a certain limit.     

Solving a relativistic quasipotential equation for a superposition of a nonlocal separable and a local quasipotential

Within the relativistic quasipotential approach to quantum field theory, a method is developed for solving a finite-difference quasipotential equation for the case where a total quasipotential describing the interaction of two relativistic spinless particles of unequal masses is a superposition of a nonlocal separable and a local quasipotential. The cases are investigated where the local component of the total interaction—it is assumed to be known—either admits or does not admit the existence of bound states. This makes it possible to obtain an exact expression for the increment of the phase shift, to determine the conditions of the existence of bound states, and to give a generalization of the Levinson theorem.     

Tunnelling process between a semiconductor or a metal and a polymer

The tunnelling lifetime of an electron lying in a p-type orbital localised at a given distance from a semiconductor or a metal is calculated by using Bardeen's method. It is then shown that even in the absence of broad bands, the hole injection process from semiconductors and metals into polymers should follow a Fowler-Nordheim dependence, provided that the current is not bulk-limited. In the semiconductor case, the current can be expressed by a fully analytical formula, and by an approximate one in the case of a metal. It is demonstrated that the effective Fowler-Nordheim barrier is not the mere difference between the metal work function or the semiconductor electron affinity and the HOMO level of the polymer, but a simple function of both levels. Received 6 April 2001 and Received in final form 29 May 2001     

Growth of a nonuniform ripple on a Gaussian beam in a plasma

In the present paper we have investigated the growth of a radially symmetrical ripple, superimposed on a Gaussian beam propagating in a plasma. The effect of the position and the width of the ripple on its growth has been studied in some detail. The present analysis considers two mechanisms for the redistribution of carriers in the plasma and the effect of redistribution on the growth of the ripple; the two mechanisms are nonuniform collision dominated heating of the carriers and the ponderomotive force arising on account of nonuniform intensity distribution. Work supported by NSF (USA) and CSIR (India).     

Formation of a bistructure of a solid in a computer experiment

Molecular-dynamics was used to investigate the structural changes occurring in a three-dimensional solid when the solid is transferred from an amorphous into a crystalline state. Crystal cells of a new type — pentadecahedrons with five square lateral faces and ten regular triangular faces at the vertices of a cell — were found for the first time in a computer experiment. It is shown that a bistructure consisting of crystal cells of different types, including cells with five-fold symmetry axes, are stable in the solid. Fiz. Tverd. Tela (St. Petersburg) 40, 1919–1924 (October 1998)