稀疏波分复用与密集波分复用的比较

稀疏波分复用（CWDM）系统的作用与WDM相同。如今部分厂商已经能够提供具有2到8个波长的商用CWDM系统，将来这些系统有望在1290nm到1610nm的频谱内扩展到16个复用波长。目前，大多数CWDM系统工作在从778nm到850nm和1470nm到1610nm的范围内，其信道间距为20nm，并可以利用大量的旧光纤（G.652光纤），节省了投资成本。硬件CWDM系统不包含线路放大器。由于器件成本和系统要求的降低，使得CWDM系统的造价比DWDM系统大幅下降。DWDM的收发设备要比CWDM系统的同类产品贵四、五倍，这与激光器的许多因素相关。CWDM的激光器与DWDM…     

粗波分复用及其扩容技术

分析比较了粗波分复用(CWDM)技术与密集波分复用(DWDM)技术的异同,总结了CWDM技术的优点与不足之处,针对CWDM系统扩容性差的缺陷,给出了目前的一些解决方案: 全波段CWDM、CWDM内嵌DWDM波长、提高单位通道传输容量.     

城域波分复用传输系统

随着城域传输网的演变和对带宽的要求，密集波分复用技术将由长途骨干网进入城域传输网。本文对城域DWDM系统的组成、波长的采用、OADM结构、波长转换器特性、光放大器的采用、波长优化、网络保护机制等进行了简要的分析。     

光波波分复用传输系统

２０年来,光纤技术的发展在当今信息时代起到了举足轻重的作用,而光波波分复用多路光纤传输系统则是光纤通信新技术领域中重要的一部分。利用现代城市电信部门的光纤通信手段,应用光波波分复用新技术,建设城市的电视监控和报警系统,实践证明是可行的。１波分复用原理光波波分复用简称为ＷＤＭ,就是在一根光纤内同时传送几个不同波长的光信号,也就是光频分制。如图１所示。在传送端将不同波长的已调光信号通过合波器Ｍ合在一起,经光纤传输将组合信号（话音、图像）传送到接收端,然而由分波器Ｄ将不同光波长的信号分开,最后送到光接…     

波分复用光纤传输系统

(一)波分复用原理波分复用的全称是波长划分多群复用(wavelength Division Multiplexing,简写为WDM),意指一根光纤同时传输两个或多个光载波,各有不同的波长,而每一光载波各自载荷一群数字信号,从几Mb/s至几百Mb/s,或载荷一路至多路模拟电视信号。图1上部所示为两个光载波的波分复用光纤系统,λ_1=1.275μm,λ_2=1.335μm。在发送端两个光波长的发送机发出的两个光波,由合波器把它们合并起来,经由同一根光纤传输。接收端的分波器把光纤传来的两个光波长分离     

光波分复用传输系统简介

简单介绍了光波分复用（ＷＤＭ）传输系统的原理和几种基本的光ＷＤＭ传输系统的结构及其适用范围，以及可用于现有光缆线路扩容改造的组合光电ＷＤＭ器件     

对波分复用系统扩容方式的探索

对在原有8/16×2.5 Gbit/s波分复用系统中增加或替换少量10 Git/s波道的扩容技术作了介绍,如波分复用终端设备改造方案,扩容工程所应用的技术及测试项目等。     

100G波分复用传输的关键技术

100Gb/s的关键技术主要体现在调制编码与复用、接收技术、FEC等多个方面。本文将将从这三个方面,介绍近期100G线路传输解决方案的最新进展与技术。     

长途传输波分复用系统的设计

随着波分复用（WDM）技术的广泛应用，在工程调测和系统的运行过程中出现了由于系统的适应能力较差和灵活性不够而引起系统优化时间过长的问题，给运营商带来了许多不便，同时，WDM已经由一般的长途应用向超长距离传输和城域网方面发展，适应性和灵活性成为WDM系统网络应用的主要要求，本文将介绍WDM系统的关键技术，重点论述WDM网络设计的一些原则，最后提出WDM系统设计的注意事项。     

Multi-pump discrete Raman amplifier for CWDM system in the O-band

We demonstrate theoretically that discrete Raman amplifiers operating in the O-band region (1260–1360 nm) are more efficient than in any other band if we consider the fiber attenuation. Compared with the C-band (1530–1565 nm), the net gain is 3 dB higher. We present also theoretically two types of discrete Raman amplifiers which can be used in the O-band with a course wavelength division multiplexing system. The first amplifier has a bandwidth of 70 nm that was designed with four pump lasers operating at 12XY nm. The second one has a bandwidth of 100 nm and needed six pump lasers to obtain a flattened gain across the O-band. In addition, we have analyzed the gain saturation in both optical amplifiers.     

Improved general lower bound for spatially-correlated Rician MIMO capacity

In this letter we derive a new closed-form lower bound on the ergodic capacity of single-sided correlated Rician MIMO channels with arbitrary-rank mean matrices. The new bound is significantly tighter than previously reported bounds, and matches almost exactly with empirically-generated (exact) capacity results for all signal to noise ratios. The new closed-form bound is also more computationally efficient than the previous bounds in the literature.     

Building cost effective lower layer VPNs: The ILEC/CLEC dilemma

Layer 2 and layer 1 Virtual Private Network (VPN) services; ranging from simple leased lines to extending private LANs across public networks, are commonplace today. With the continuously growing economic difficulties, capital meltdown, and telecommunication business turmoil, delivering those VPN services at the lowest cost or with the maximum revenue margin, while committing to Service Level Agreements (SLA), has become essential. We show that whether we tackle the optimal VPN design problem from an Incumbent Local Exchange Carrier (ILEC) standpoint or from a Competitive Local Exchange Carrier (CLEC) standpoint, we obtain contradictory rules. We show that by building Edge Disjoint VPN trees and spreading the traffic all over the network, the ILEC can achieve maximum throughput and enhanced network performance; while by concentrating all the VPN traffic over a single tree, the CLEC can minimize the cost of leased bandwidth. We then propose two simple algorithms that can help carriers and service providers leverage their networks and increase their revenue margins while meeting SLA requirements. Copyright © 2010 John Wiley & Sons, Ltd.     

用于高压、高容量电池系统的低成本isoSPI耦合电路

本文介绍了一种采用AC耦合方法可以减轻高压iso SPI系统的成本问题,无需要求磁性元件提供双重绝缘。用价格不贵、缠绕在绕线管上的共模扼流圈(CMC)组件取代专门的螺旋管型变压器磁性元件,进一步降低成本。电容器和CMC都是相对扁平的表面贴装芯片组件,价格富有竞争力,而且其高可靠性经过审查,可用于汽车系统。用于AC耦合的偏置电阻器为监视系统的电介质完整性提供了一种非常有用的途径。     

CWDM在城域网建设中的应用

城域网建设中普遍存在着光纤短缺的问题，CWDM为运营商提供了低成本的解决方案。对CWDM和DWDM的成本进行比较，介绍CWDM的主要技术参数，并对CWDM技术的发展方向及其在城域网建设中的应用位置作了简要说明。     

On the path-loss attenuation regime for positive cost and linear scaling of transport capacity in wireless networks

Wireless networks with a minimum inter-node separation distance are studied where the signal attenuation grows in magnitude as 1/ρ/sup δ/ with distance ρ. Two performance measures of wireless networks are analyzed. The transport capacity is the supremum of the total distance-rate products that can be supported by the network. The energy cost of information transport is the infimum of the ratio of the transmission energies used by all the nodes to the number of bit-meters of information thereby transported. If the phases of the attenuations between node pairs are uniformly and independently distributed, it is shown that the expected transport capacity is upper-bounded by a multiple of the total of the transmission powers of all the nodes, whenever δ>2 for two-dimensional networks or δ>5/4 for one-dimensional networks, even if all the nodes have full knowledge of all the phases, i.e., full channel state information. If all nodes have an individual power constraint, the expected transport capacity grows at most linearly in the number of nodes due to the linear growth of the total power. This establishes the best case order of expected transport capacity for these ranges of path-loss exponents since linear scaling is also feasible. If the phases of the attenuations are arbitrary, it is shown that the transport capacity is upper-bounded by a multiple of the total transmission power whenever δ>5/2 for two-dimensional networks or δ>3/2 for one-dimensional networks, even if all the nodes have full channel state information. This shows that there is indeed a positive energy cost which is no less than the reciprocal of the above multiplicative constant. It narrows the transition regime where the behavior is still open, since it is known that when δ<3/2 for two-dimensional networks, or δ<1 for one-dimensional networks, the transport capacity cannot generally be bounded by any multiple of the     

On the lower bound of zero-error capacity (Corresp.)

It is shown that the lower bound on zero-error capacityC_{0}as presented by Shannon [1] and Gallager [2] isln alpha, wherealphais the maximum number of channel input symbols, no two of which have a common output symbol.     

CWDM技术在通信网络中的应用分析

文中首先对CWDM技术进行了介绍,包括CWDM的系统组成和系统原理等,然后以城域网为例分析了CWDM技术在通信网络中的应用,并总结了CWDM技术在通信网络中的优势,最后提出了一些可行的应用维护意见。综上所述,目前CWDM在城域网、接入网、企业网、校园网等领域具有广泛的应用前景。     

The intersymbol interference channel: lower bounds on capacity andchannel precoding loss

The discrete-time additive Gaussian intersymbol interference (ISI) channel with i.i.d. (not necessarily Gaussian) input signals is considered. Several new and old lower bounds on the capacity are derived in a unified manner by assuming different front-end receiver filters, in particular the sampled whitened matched filter (SWMF) and the minimum mean-squared error-decision feedback equalizer (MMSE-DFE) filter. The features of the bounds are demonstrated and compared in several examples with binary and quaternary input signals. It is also shown that the effect of an ideal post-cursor or tail cancellation, in an information-preserving context, depends primarily on the front-end filter. While, as is well known, ideal post-cursor cancellation at the output of the SWMF decreases the information, the opposite trend is seen when an MMSE-DFE front filter is considered. This observation reflects the basic theoretical obstacles in precoding, i.e., ideal post-cursor cancellation in the presence of a pre-cursor. It is used to assess the inherent loss (in terms of information rates as compared to the rates achievable with the hypothetical ideal post-cursor cancellation) associated with any post-cursor cancellation technique such as precoding, DFE, or other variants, when operating in synergy with the MMSE-DFE front-end filter. The effect of the front-end filter on an ideally interleaved, precoded coded-modulation system is also addressed