新颖的双通道输出高功率掺铒光纤宽带光源

在分析L波段放大自发辐射(ASE)谱产生原理的基础上,设计出一种新颖的双级结构掺铒光纤ASE宽带光源,该光源可在两个端口分别输出高功率的C波段和L波段的ASE谱.设计将C波段ASE谱注入到掺铒光纤中作为L波段ASE谱的二次抽运源,使得L波段ASE谱功率得到了有效提高.优化光源结构参量后从两个端口分别获得了12.97 dBm和12.81 dBm的C波段和L波段ASE宽带谱.将两个输出端口组合得到了功率为15.9 dBm,泵浦转换效率达到21.6%的C+L波段超宽带ASE光源.     

光声光谱技术在多组分气体浓度探测中的应用

CO和CH_4气体作为判断变压器运行状态的故障气体,对其浓度的探测在变压器维护中具有重要意义.为了准确探测变压器运行过程中产生的CH_4和CO气体浓度,本文利用光声光谱技术,设计了一套基于宽带光源的多组分气体探测系统,和共振型光声系统相比,该系统中所用的非共振型光声池体积小,易加工,池内各处信号强度相同,降低了对声学信号探测器的安装要求.系统的性能通过对CO和CH_4气体的探测进行评估.首先,从理论上分析了信号强度与调制频率呈反比,然后根据宽带光声系统在不同调制频率下的响应,确定系统的最佳调制频率为22 Hz.在最佳调制频率下,根据温度与待测气体光声信号的关系,对光声信号进行温度补偿,消除温度变化对光声信号的影响,进一步提高了系统的稳定性.最后,通过不同浓度的CH_4和CO气体对系统进行标定.实验表明,温度补偿前后,光声信号随温度的漂移分别为0.023 23V/℃和8.383 48×10~(-5) V/℃,通过对不同浓度CH_4和CO气体的探测,系统的线性度分别达到0.995和0.998 4.在一个大气压下,积分时间为1s时,宽带光声探测系统对CO和CH_4气体的探测极限浓度能够达到1μL/L.该系统成本低,线性度好,探测灵敏度符合国标对变压器维护过程中CO和CH_4气体的探测要求.     

Approximate and Exact Small Signal Analysis for Single-Mode Fiber Near Zero Dispersion Wavelength with Higher Order Dispersion

This article presents the comparison of approximate and exact small-signal theories for analyzing the influence of the higher-order dispersion terms on dispersive optical communication systems operating near zero dispersion wavelength for linear single-mode fiber. For the approximate theory, the generalized conversion matrix has been reported and gives the transfer function of intensity and phase from the fiber input to fiber output for a laser source including the influence of any higher-order dispersion term. In addition, expressions for the small-signal frequency response and the relative intensity noise (RIN) response of an ultrafast laser diode including noises are derived. However, it is observed that the approximation assumed for the second-order dispersion term for the approximate analysis is not valid. From the approximate theory, the exact generalized conversion matrix and exact expressions for small-signal frequency response and relative intensity noise (RIN) are obtained. We show that for the exact theory, the second-order dispersion term has no effect on intensity and frequency response even at large modulating frequencies and large propagation distances contrary to the approximate theory as reported by other authors. But we show that third-order dispersion term certainly has some minute impact on the frequency and RIN response for long distance links at high modulating frequencies.     

宽带匹配网络设计中的改进实频法

通过对传输功率增益TPG的进一步推导,引入了共轭匹配原理,提出了一种对实频法的改进算法,运用最小二乘法直接求取电阻折线各段的增量值,避免了对增量的最初选取,简化了计算。用改进实频法设计了一个短波天线宽带匹配网络,在简化算法的基础上取得了比较好的性能。     

Adaptive resource allocation techniques in OFDMA using cross-layer architecture

This paper utilizes the cross-layer architecture to implement adaptive resource allocation in Orthogonal Frequency Division Multiple Access （OFDMA） based on the broadband wireless access system. According to the cross-layer architecture, the information in link layer is used for adaptive resource allocation in OFMDA. A new cross-layer adaptive resource allocation algorithm is developed which can guarantee the users to be in minimum average waiting time in link-layer and get the better spectrum utilization. Numerical results show that our scheme is appealing and can get about half of average waiting time less and 0.5 bps/Hz spectrum utilization more than the scheme in 1EEE802.16a.     

Policy options for broadband infrastructure strategies: A simulation model for affordable universal broadband in Africa

Goal 9 of the Sustainable Development Goals aims to provide universal affordable broadband globally. However, a lack of data, combined with few independent and scientifically reproducible assessments, makes it challenging for governments to make strategic choices to achieve this goal. Therefore, new research approaches are required to support decision evaluation. This paper demonstrates an innovative method that addresses data and model uncertainty by developing open-source software to explore affordable universal broadband strategies, using a scenario-based hypothetical mobile operator. Targets being considered by the United Nations’ Broadband Commission are evaluated, with the financial costs of different infrastructure decisions quantified for the whole of the African continent. The results suggest that ‘leapfrogging’ to 4G is more cost efficient than 3G for providing universal broadband, with savings between 7 and 57 % for 10 GB/Month and 20–47 % for 30 GB/Month. The baseline 4G cost for connecting all unconnected and underserved users across Africa is $0.4 trillion for 10 GB/Month and $0.7–1 trillion for 30 GB/Month.     

LMDS宽带无线接入技术

本地多点分配业务（LMDS）是解决通信网接入问题的有效技术,国际电联规划的LMDS可用频带比DBS、MMDS的要宽得多。LMDS系统包括基站系统、用户端设备和网络管理系统,可以提供多种业务。目前LMDS的商用系统已经正式投入运营,我国也已在广州等城市开展了LMDS的测试工作。     

浅析新格局背景下的增值电信企业生存之道

日前,工信部发布《中国(上海)自由贸易试验区外商投资经营增值电信业务试点管理办法》,不仅新增开放了四项业务并提高开放业务的外资最高持股比例,还将审批权限由工信部下放到上海市通信管理局,把审批期限大幅缩短至两个月。此次在上海自贸区试点开放的增值电信业务,力度非常大,全部8项增值电信业务中有7项在这里进行了开放试点。4月30日,经国务院批准,财政部和国家税务总局印发《关于将电信业纳入营业税改征增值税试点的通知》,明确从2014年6月1日起,将电信业纳入营改增试点范围,实行差异化税率,基础电信服务和增值电信服务分别适用11%和6%的税率,为境外单位提供电信业服务免征增值税。在如此鼓励国际化竞争的新格局背景下,国内的增值电信服务企业应如何应对政策及市场的机遇与挑战。     

ATM交换的优先控制方式

本文对采用ATM体制的宽带综合业务数字网业务流的优先控制进行了研究，提出了两种新的优先控制方法。     

The impact of facilities and service-based competition on internet services provision in the Canadian broadband market

A variety of studies have focused on the effect of competition in broadband markets on increasing broadband penetration rates. Few studies however have focused on the extent to which competition also results in innovation in the marketplace, as demonstrated by increased broadband speeds, and other improvements that provide value to broadband users. This paper considers the effectiveness of market competition as a means of encouraging broadband providers to offer innovative services that meet citizens’ increasing needs for affordable high quality and high speed broadband connectivity. The study focuses on the provision of broadband services in Canada, a country where consumers were early adopters of broadband and where the policy environment has encouraged competition in the broadband market from its inception. Drawing on data from the OECD and the Canadian Radio-television and Telecommunications Commission (CRTC), the paper demonstrates that Canada’s regulatory regime does not appear to be sufficient to enable a competitive marketplace that results in the provision of innovative broadband services.