海底光缆探测中信号衰减的特性研究

海底光缆故障定位主要采用电场法和磁场法,文章根据传输理论,分别推导了这两种方法下信号在海缆导体中的衰减公式,分析了其衰减特性.数值仿真表明:当故障点与岸端距离达1 000 km时,在某型号海缆中,使用磁场法探测,衰减超过95％;而使用电场法探测,则不到8％,在抗衰减方面,电场法要远远优于磁场法.     

国际海缆发展小史

1951.11.英国铺设成功穿越多佛尔海峡的电报海缆线路。这是世界上第一条海底电缆线路。1866.7. 英国又铺设了穿越大西洋的电报海缆。1902. 英国铺设绕世界一周、连接各英联邦国家的电报海缆网“All Red Route”。1903. 美国铺设成功旧金山-夏威夷-关岛-马尼拉的电报海缆。1966.8. 日本和美国联合铺设了东京-关岛的电报海缆。1956.9. 美国研制成功采用可挠型海缆中继器的双股式深海用同轴海缆,用SB方式。在美     

一种海底光缆断点探测与定位技术

提出了利用电磁感应原理探测和定位海缆断点的解决方案——海底光缆无源探测系统，并在此基础上详细分析了系统的工作原理，最后给出探测、定位的具体方案。     

快速查找同轴电缆断点小窍门

介绍一种快速查找同轴电缆断点的方法,以供参考. 取1 m左右的-5线,将一端的护套和绝缘体去掉,使内导体和外导体各露出0.8 m,做成全方位天线状;将另一端做成F头,固定在场强仪上.然后持场强仪在电缆下来回走动,察看在一个频段内某一频道信号的变化情况,当发现在某处信号电平最大时,即可判断出这里是断点的大概位置.然后观察、动手触摸作进一步判断,最后确定断点的准确位置.     

复合海底电缆顺-逆扭转特性对比研究

复合海底电缆在敷设和运行过程中由于外部荷载作用常发生扭转行为.文章基于有限元软件建立三芯光纤复合海底电缆局部段的精细数值模型,并开展了相关数值仿真实验,重点研究海缆顺-逆扭转方向以及扭转角度对海缆主要结构的受力影响.仿真结果表明,顺-逆扭转作用对于不同绞合方向的内部结构有不同程度的影响,海缆内部结构沿轴向方向扭转角度具...     

基于光纤光栅水听器的海缆安全监测方法研究

提出了在海缆中嵌入光纤光栅水听器监测海缆附近的拖锚情况,实现在海缆受损前采取措施的安全预警方法;分析了声源特性,并基于台湾海峡建立声场模型,对TL(声传播损失)进行了仿真。仿真结果表明,当各水听器间的距离为500 m时,该方法可以确定海底光缆沿线约1km范围内声源的位置。     

一种被动式海缆路由探测技术研究

海缆的路由探测和故障点定位技术是海缆维护工作中的关键技术之一.文章针对目前常用探测方法的缺点和不足,提出了被动式海缆路由探测技术.首先介绍了被动式海缆路由探测的系统原理,然后在此基础上提出了该系统的设计方案,最后,给出了该系统的有效仿真方法及仿真结果.仿真结果表明:电压衰落斜率越大,线圈与光缆间的距离越远.因此被动式海缆路由探测系统可有效地对海缆进行路由跟踪和定位.     

基于TDR的ADSL线缆断点测试仪设计

介绍一种基于时域脉冲回波(TDR)原理的ADSL线缆断点测试系统.该系统设计以STC单片机为控制核心.以FPGA为测试主体发射接收脉冲,采集脉冲往返线缆时间,实现ADSL线缆断点位置的测量.在分析现有测试产品的基础上,首先阐述设计理论,然后介绍系统总体设计框图、硬件实现、软件测试流程以及系统实际测试结果.实验结果表明该测试仪能够快速准确测试出断点位置,并且只需适当剪切,便可作为内嵌模块应用于其他仪表.     

基于布里渊散射原理的在线海缆监测系统

针对海缆重量与长度大、造价高和周期长、工程风险高、维修难度大的缺点,提出了基于布里渊散射原理的在线海缆监测系统。该系统包括数据采集硬件和信息处理软件两部分,数据采集部分用于采集与传输海缆电源谐波信息、温度信息和应变信息;信息处理软件部分用于实现信息的接收、显示和分析等数据处理功能。实验与测试结果表明,该系统能实时获取海缆的温度及应力形变信息,及时定位海缆的故障位置,达到实时监测与预警的目的。     

我国第一条直接敷设的多层铠装海底通信光缆选型

本文以我公司朱家尖一六横输电线路海底通信光缆工程为例,分析了海底通信光缆的施工敷设方法和光缆结构,首次应用了非埋设海缆的位置稳定性原理,圆满完成我国第一条直接敷设的多层铠装海底通信光缆的结构选型和施工,取得了良好的效果。     

基于FDTD方法的同轴电缆孔缝辐射效应研究

利用时域有限差分法(FDTD)研究了同轴电缆传输数字脉冲信号时的孔缝辐射效应。文中首先推导了三维柱坐标系下完全匹配层(PML)的差分表达式，并给出保证其解稳定性的更为严格的时间步长公式。然后利用FDTD法分析了数字信号经同轴电缆孔缝的辐射效应，对孔缝内外的电磁场及其远场进行了数值分析和计算。处理孔缝边界时，用级数展开和积分方程得到金属拐角处电磁场的近似解。最后对结果进行了分析。     

Antenne unipolaire cylindrique alimentée par un cable coaxial. problème des singularités et applications en basse fréquence

In the integral equation approach to the antenna radiation problem, the current on the antenna and an accurate modelization of the generator are needed. Moreover the kernel of the integral equations is singular. This paper, presents a rigorous solution of these equations in the case of a wire antenna mounted on a perfectly conducting plane, and feeded by a coaxial cable. The current on the antenna and the field inside the cable are accurately determined. At low frequencies, the techniques used to avoid the singularity in the kernel allows a fast computation of the unknown current and field.     

Scattering of Guided Modes Caused by an Arbitrarily Shaped Broken End in a Dielectric Slab Waveguide

Electromagnetic scattering of guided modes in a dielectric slab waveguide caused by an arbitrarily shaped broken end is analyzed theoretically by using the integral equation method. By solving the integral equations iteratively, the tangential components of the electric and magnetic fields on the broken end surface are determined, from which the reflected mode power, the radiation wave power and field patterns, and the total scattered power are obtained. Numerical results are presented for the plane-perpendicular, plane-tilted, and arc-shaped end surfaces. Both TE and TM modes are assumed as an incident wave.     

Fields generated by bare and insulated cables buried in a lossyhalf-space

The propagation constants and resulting fields for the current excited on bare and insulated cables buried in a lossy Earth medium are examined. The fields are formulated in integral form under the thin-wire approximation. The discrete mode propagation constants for the insulated and bare cable types have dramatically different behavior, and subsequently affect the radiated fields. Unlike the insulated cable, it is shown that for the bare conductor the accurate determination of the propagation constant is imperative in the calculation of some of the field quantities at the Earth's surface. Simple near-field expressions are developed from the integral forms and numerical results are presented for various cable structures and burial depths. The study implies that the use of various commonly utilized approximations, such as the uniform axial current assumption, may not be valid for the bare or grounded buried conductors     

Optical cable fault location using correlation technique

The letter describes a correlation based optical cable fault location technique which, using a 1.3 ?m wavelength, can detect a broken point 10 km distant from source.     

电磁脉冲对电缆耦合问题的理论研究

为克服传输线方程求解电磁脉冲电缆耦合问题的不足,提出了有限差分求解电场积分方程的方法,解决了架空电缆电磁脉冲耦合效应的数值模拟难题;引入了基于细线散射的时域有限差分法,解决了地面铺设电缆电磁脉冲耦合效应的数值模拟难题。利用时域电场积分方程方法研究了长度、线径等电缆参数变化及脉宽、极化方向等馈源参数变化对其电磁脉冲耦合效应的影响。给出了电缆耦合电流的波形特征、沿线分布规律。研究表明:在电磁脉冲作用下,自由放置的电缆,其感应皮电流为衰减振铃波形;电流最大值出现在电缆的中心处;随着电缆长度的增加,电缆上的感应皮电流非线性变大;电缆线径的增加、脉冲宽度的改变对其耦合电流峰值影响较小;电场的极化方向对电缆感应皮电流的影响较大。     

Analysis of a novel expanded tip wire (ETW) antenna for microwave ablation of cardiac arrhythmias

A novel expanded tip wire (ETW) catheter antenna is proposed for microwave ablation for the treatment of atrial fibrillation (AF). The antenna is designed as an integral part of coaxial cable so that it can be inserted via a 6F catheter. A numerical model based on the rotationally symmetric finite-difference time-domain technique incorporating the generalized perfectly matched layer as the absorbing boundary condition has been utilized to accurately model the interaction between the antenna and the myocardium. Numerical and in-vitro experimental results are presented for specific absorption rate, return loss and heating pattern produced by the antenna. Both numerical modeling and in-vitro experimentation show that the proposed ETW antenna produces a well-defined electric field distribution that provides continuous long and linear lesions for the treatment of AF.     

Transient response of the infinite cylindrical antenna and scatterer

The transient response of an infinite cylindrical antenna and scatterer is obtained by time gating a time-dependent electric-field integral equation for thin wires of finite-length. The driving point current and broadside radiated field approximate the driving point voltage in the antenna case, while the current excited in the scattering case approximates the time integral of the incident field. This approximate integral relation is used to estimate currents excited on cylindrical structures without employing the complete integral equation solution procedure.     

Rigorous Analysis of Rectangular Dielectric Resonator Antenna With a Finite Ground Plane

A probe-fed rectangular dielectric resonator antenna (RDRA) placed on a finite ground plane is numerically investigated using method of moments (MoM). The whole structure of the antenna is exactly modeled in our simulation. The feed probe, coaxial cable and ground plane are modeled as surface electric currents, while the dielectric resonator (DR) and the internal dielectric of coaxial cable is modeled as volume polarization currents. Each of the objects is treated as a set of combined field integral equations. The associated couplings are then formulated with sets of integral equations. The coupled integral equations are solved using MoM in spatial domain. The effects of ground plane size, air gap between dielectric resonator and ground plane, probe length, and position on the radiation performance of the antenna including resonant frequency, input impedance, radiation patterns, and bandwidth are investigated. The results obtained for the antenna parameters based on the MoM investigation shows that there is a close agreement with those obtained by measurement. Moreover it is shown that the MoM results are more accurate than other simulation results using software package such as High Frequency Structure Simulator (HFSS).