矿井感应通信机车插入损耗及专用线理论研究

给出了在矿井中利用电机车架空线进行感应通信时，架空线负载（即电机车）引起的手稿损耗的定义，计算了插入损耗和无负载时的电磁波传输损耗并对比了这两种损耗，可知插入损耗是非常大的，这说明了使用专用感应线的必要性，架设专用感应线后，矿井隧道中将存在一个插入损耗和传输损耗都比较小的波模，利用该波模进行感应通信是可行的。     

VoIP丢包处理技术的研究进展

阐述了VoIP丢包的主要原因，并介绍了当前常用的解决丢包问题的相关技术。其中，丢包处理技术是用来恢复或隐藏当发生丢包时所造成的损失的相关技术，包括丢包隐藏和丢包恢复；而抗丢包技术的目的是避免网络拥塞，减少丢包率。另外，还给出了VoIP当前的研究现状，论述了其发展趋势。     

A Bayesian Approach to Reliability Estimation Using a Loss Function

A Bayesian estimate of reliability for the exponential case is developed which utilizes the basic notion of loss in estimation theory. Since the loss associated with overestimation is usually greater than the loss associated with underestimation of reliability, the loss function can be a useful tool. The loss function and prior distribution of reliability presented are sufficiently flexible to be compatible with many situations in which reliability estimates are require. When no prior information is at hand and a symmetric loss is used, the resulting estimate is seen to be the minimum variance unbiased estimate of reliability. This agreement gives some credibility to the precision of the estimation approach.     

基于子树丢包模式的链路丢包率快速推断算法

为提高网络链路丢包率的测量速度,本文提出一种基于子树丢包模式的链路丢包率推断算法.该算法通过选择合理的链路丢包率初始值以减少迭代次数;根据端到端测量结果将网络拓扑划分为传输状态确定性区域和非确定性区域,避免确定性区域冗余分解造成的时间开销;通过对非确定性区域子树丢包模式按层分解,以子树丢包模式为基本计算单元,减少非确定性区域链路丢包的重复分解过程,提高链路丢包率计算速度.仿真结果表明,该算法能在不损失测量精度的前提下,减少链路丢包率测量总时间,提高测量速度.     

Spectral analysis of packet loss rate at a statistical multiplexerfor multimedia services

Uses the well known technique of power spectral representation to characterize the second order statistics of packet loss during congestion at a statistical multiplexer. Unlike the steady state statistics, the second order statistics measures the time correlation behavior of loss. Typically, the low frequency loss power is associated with long periods of highly consecutive loss. The effect of the loss rate power spectrum on transmission qualities is service dependent. The study indicates that, by selective packet discarding, one can properly change the distribution of the overall loss rate spectrum among the multiplexed traffic streams, which can significantly improve the transmission quality of individual services. Moreover, with the design of multi-level buffer overload control, one can tune the loss rate steady state distribution of different priority streams to a piece-wise step function, which minimizes the packet loss impact on service qualities     

标准单模光纤宏弯曲损耗的理论研究

文章给出了多包层标准单模光纤的宏弯曲损耗模型,这一损耗模型不仅适用于多包层单模光纤的宏弯曲损耗的计算,也适用于单包层单模光纤的宏弯曲损耗的计算.文章还讨论了弯曲半径及工作波长与单模光纤弯曲损耗之间的关系,并把这种关系与传统的弯曲损耗模型进行了比较,比较结果表明,单模光纤包层对弯曲损耗有很大的影响.此外,文章还运用模式耦合理论详细解释了廊(Whispering-gallery,WG)模对损耗振荡的影响.     

Bragg光纤色散和损耗特性的全矢量有限差分分析

利用全矢量有限差分方法分析了空气纤芯Bragg光纤中模式的色散和泄漏损耗特性,并结合光子带隙图,讨论了其中TE01模和HE11模泄漏损耗的变化趋势.当色散曲线由光子禁带进入光子导带,模式的泄漏损耗将相应地明显增大;此外,当λ1.49μm时,HE11模的截止引起了泄漏损耗的急剧上升.这表明,Bragg光纤中,模式泄漏损耗的增加至少可以归结于两种不同的机制:模式失去光子带隙的约束和模式截止.同时,通过分析发现,其中高阶模的截止条件类似于金属波导;这是Bragg光纤与金属波导特性具有一定相似性的又一例证.     

配电网线损分析和降损策略分析

发电的电能变成高压通过电网输送至供电地区,之后由变电站降压处理后提供给用户。这个过程不可避免的损失一部分电能,该损失即为线损。在供电过程中线损无法杜绝,但供电企业为了提高管理水平积极思考怎样降低线损,并且在降低线损时增加企业效益。近些年来,供电企业在线损管理中引入新技术,主动实行降损处理,帮助企业实现节能增效。     

A Consideration of an Optical Coupler for Optical Submarine Transmission Laser Redundancy Systems

Theoretical and experimental results are described for a new optical coupler which consists of two laser diodes, two GRIN spherical rod lenses, a polarizing filter, and a single-mode fiber, and which employs laser diode polarization characteristics for an optical submarine transmission laser redundancy system. This optical coupler has two channels at 1.3 μm wavelength. Optical coupler loss values, which include coupling loss, polarization loss, and assembly loss, are 4.9 dB for one laser diode and 5.2 dB for another laser diode. Such loss values are almost the same as the conventional laser diode module loss for a single-mode fiber. This paper describes in detail a laser redundancy system in an optical submarine transmission system, structure and characteristics of an optical coupler, and experimental results on a high bit rate long-haul transmission system using the proposed optical coupler.     

Absolute QoS differentiation in optical burst-switched networks

A number of schemes have been proposed for providing quality-of-service (QoS) differentiation in optical burst-switched (OBS) networks. Most existing schemes are based on a relative QoS model in which the service requirements for a given class of traffic are defined relative to the service requirements of another class of traffic. In this paper, we propose an absolute QoS model in OBS networks which ensures that the loss probability of the guaranteed traffic does not exceed a certain value. We describe two mechanisms for providing loss guarantees at OBS core nodes: an early dropping mechanism, which probabilistically drops the nonguaranteed traffic, and a wavelength grouping mechanism, which provisions necessary wavelengths for the guaranteed traffic. It is shown that integrating these two mechanisms outperforms the stand-alone schemes in providing loss guarantees, as well as reducing the loss experienced by the nonguaranteed traffic. We also discuss admission control and resource provisioning for OBS networks, and propose a path clustering technique to further improve the network-wide loss performance. We develop analytical loss models for the proposed schemes and verify the results by simulation.     

Si基集成光学陀螺中弯曲波导特性研究

给出了Si基集成光学陀螺的光路结构,理论计算了余弦型弯曲波导的弯曲半径和弯曲损耗。仿真分析了弯曲波导的宽度、长度与弯曲损耗的关系,进而设计了集成光学陀螺用"K"形耦合器,并通过R-soft软件进行了仿真分析。搭建了弯曲波导的实验测试装置,分别测试了弯曲波导的传输损耗与光模场,结果表明,波导单位损耗为0.014dB/cm,验证了理论计算结果的正确性。采用光束扫描法测试了弯曲波导的模场,实验结果与理想高斯拟合曲线吻合。     

光纤横向错位损耗分析及应用研究

本文对光纤连接时的横向错位损耗进行了仿真分析，利用损耗与错位量之间的关系，可以设计出结构简单，回波损耗较高的光衰减器。     

光纤横向错位损耗分析及应用研究

本文对光纤连接时的横向错位损耗进行了仿真分析,利用损耗与错位量之间的关系,可以设计出结构简单,回波损耗较高的光衰减器。     

利用衰减钮扣抑制耦合腔行波管的上边频振荡

耦合腔行波管由于其结构的特点,很容易产生白激振荡。采用在耦合腔腔壁中安装衰减钮这一谐振损耗技术可以有效地抑制耦合腔行波管中常见的带边振荡。但在实际应用中,遇到了满足要求的衰减钮扣的衰减材料的相对介电常数过小而不能制备的情况,此时通过改变衰减钮扣的结构——变实心衰减钮扣为衰减环,可以成功的解决这一难题。本文主要对这一方法的基本理论和在实际中的具体应用进行论述。     

Optical coupler for laser redundancy system

Experimental results are described for a new optical coupler, which consists of two laser diodes, two GRIN spherical rod lenses, a polarised filter and a single-mode fibre, and employs laser diode polarisation characteristics for an optical submarine transmission laser redundancy system. This optical coupler has two channels at a 1.3 ?m wavelength. Optical coupler loss, which includes coupling loss, polarisation loss and assembly loss, is 4.9 dB for laser diode 1, and 5.2 dB for laser diode 2.     

Low-loss fibre-coupled waveguide directional coupler modulator

We report a fibre-coupled Ti: LiNbO3 directional coupler modulator with total fibre-device-fibre insertion loss as low as 1.5 dB for ?=1.32 ?m. Low loss has been achieved by using diffusion parameters to give good mode match to the fibre and low propagation loss, an effective SiO2 buffer layer to eliminate electrode loading loss and a directional coupler geometry which minimises the effect of bend loss.     

A simple formula for calculation of power loss in digitaltransmission lines

Presented is a two-parameter model of line loss in which the frequency dependence of loss is determined by way of the loss at the selected frequency and the conductor diameter. The model quite faithfully represents the actual loss of the line, and is much better than the often used √f model     

Applications of the upside-down normal loss function

The upside-down normal loss function (UDNLF) is a weighted loss function that has accurately modeled losses in a product engineering context. The function's scale parameter can be adjusted to account for the actual percentage of material failing to work at specification limits. Use of the function along with process history allows the prediction of expected loss-the average loss one would expect over a long period of stable process operation. Theory has been developed for the multivariate loss function (MUDNLF), which can be applied to optimize a process with many parameters-a situation in which engineering intuition is often ineffective. Computational formulae are presented for expected loss given normally distributed process parameters (correlated or uncorrelated), both in the univariate and multivariate cases     

因特网中分组语音传输的丢包恢复技术浅述

在基于IP网络下进行语音通信的过程中，不可避免地会遇到数据包丢失现象，极大地影响了传输服务的质量。对此问题展开讨论，讲述了丢包的原因，对当前普遍采用的几种丢包恢复技术进行了介绍，通过比较提出了自己的观点。