日本富士通在150km路径上进行了1.1Tb/s WDM传输实验

WDM技术能大幅度提高光纤通信系统的传输容量，尤其对适应性强的多媒体网络很有吸引力，它可以把整个光传递网络提高一个崭新等级。日本富士通对此作了一系列传输实验。其中有在150km的线路上，采用零色散单模光纤（SMF）配以前置放大器、宽带EDFA，再采用带负色散时隙的色散补偿光纤，进行了总速率达1．1Tb／S的传输实验。实验系统用了46只分布反馈激光器和9只外腔可调激光器作光源，用1．48μm掺饵光纤放大器作预放、线路中继器和前置放大器。该掺饵光纤放大器的显著特点是在非饱和区可获得较宽波长范围。放大器间距50km。信号经传输…     

全光网中的光信噪比估算与系统设计

指出了WDM光传送网中 ,级联光上下路节点或光交叉连接节点后 ,系统构成上与传统级联线路放大器情况下的差异以及常用光信噪比评估公式的近似性。对WDM光传送网中线路给出了一个等效模型 ,并详细推导了光信噪比的计算公式 ,同时计入了光放大器的自发辐射噪声引起的饱和效应。最后针对不同系统配置情况进行了光信噪比的估算 ,分析了估算结果及其对线路设计的指导意义     

拉曼放大器在WDM系统中的应用

拉曼放大器最空出的优点是能放大传输窗口中的任何区域。在宽带WDM系统的应用中,拉曼放大器通过对多个泵浦的复用可以使言辞大的信号带宽达到80nm。而在双向WDM系统中,拉曼放大器对L波段信号有很好放大的特性。     

电子管音响前置放大器

本文介绍一台易制、低价的电子管立体声前置放大器。该放大器有过载电平显示,且增益可调,为此,可将放大器与任何音响系统配接。1.电路工作原理电路包括三个部分,即电源部分,左、右声道放大器部分(如图1所示)。图1中的两声道放大器采用6J6电子管,该管跨     

用CD和LP听评五款前置放大器

在音响设备中前置放大器是一种包含信号处理内核的放大设备。在CD已成为音频信号源的主流的今天，有的人对前置放大器存在的必要性提出了异议。为此收集了五种较为高档的前置放大器，用CD碟片和LP唱片播放音乐，对前置放大器的音质进行试听，探索每种放大器独有的个性。并用示波器测量了每个前置放大器输出的方波波形用作参考。     

用CD和LP听评五款前置放大器

在音响设备中前置放大器是一种包含信号处理内核的放大设备。在CD已成为音频信号源的主流的今天，有的人对前置放大器存在的必要性提出了异议。为此收集了五种较为高档的前置放大器，用CD碟片和LP唱片播放音乐，对前置放大器的音质进行试听，探索每种放大器独有的个性。并用示波器测量了每个前置放大器输出的方波波形用作参考。     

捕捉靓音“闪光”点 发烧更上一层楼——两款前置名器H-1E/PE-6000的高招

在高级音响制品中,人们花功夫最多的首当其冲要数与音源配接的前置放大器。与各种信号源连接,匹配问题、噪声问题、线性放大问题、电源问题、与功放耦接问题……。一处不慎,满盘皆输。本文介绍的H—1E和PE—6000前置放大器,功力不凡,颇有几分名机风度。以下聊叙该机几处“风景点”,以飨读者。     

具有新型保护电路的磁共振接收线圈研制

低输入阻抗前置放大器在磁共振成像接收线圈中的广泛使用,使得对前置放大器的保护成为接收线圈设计的重点。文中设计制作了带有新型保护电路的磁共振接收线圈,使用失谐信号作为触发信号控制前置放大器电源的开断,并在线圈谐振回路和前置放大器之间产生高阻状态以保护前置放大器输入端。测试结果表明,各部分电路可稳定工作。该电路可用于多通道接收线圈并对于磁共振线圈的设计有启发意义。     

国际光放大器新进展

光放大器是光通信中的关键器件之一。光纤放大器不仅解决了衰减对光网络传输速率与距离的限制,并开创了1550nm波段的波分复用（WDM）,使超高速、超大容量、超长距离的WDM。     

德颂S/N极高的R10感觉宽裕的R30

德颂推出的旗舰级前置放大器和双单声道结构的前置主放大器 由德颂制造的得意之作——前级放大器R10和前置主放大器R30发售。 首先惊讶于前置放大器R10牢固的机箱。虽然是这个价格，采用的却是坚固的铝制单体结构机身。     

A 6-Bit 1.6-GS/s Low-Power Wideband Flash ADC Converter in 0.13-$mu$ m CMOS Technology

In this work, a new termination technique for the averaging network of the flash analog-to-digital converter (ADC) input preamplifiers is devised. The proposed technique eliminates the over-range voltage headroom consumed by the dummy preamplifiers and therefore, the input capacitance and power dissipation of the ADC is reduced. This technique is applied to the design of a 6-bit 1.6-GS/s flash ADC in 0.13-$mu$ m CMOS technology. The measured peak INL and DNL are 0.42 LSB and 0.49 LSB, respectively. The ADC achieves an effective resolution bandwidth (ERBW) of 800 MHz and an SNDR of 30 dB at 1.45-GHz input signal frequency while consuming 180 mW.      

A low power 12-bit 200-kS/s SAR ADC with a differential time domain comparator

A low power 12-bit 200-kS/s SAR ADC is proposed.This features a differential time domain comparator whose offset is cancelled by using a charge pump and a phase frequency detector instead of the preamplifiers usually needed in a high resolution comparator.The proposed ADC is manufactured in 0.18-μm CMOS technology and the measured SNR and SNDR are 62.5 dB and 59.3 dB,respectively,with a power consumption of 72μW at a 200-kS/s sampling rate.The device operates with a 1.8-V power supply and achieves a FOM of 477 fJ/conversion-step.     

Practical limitations on optical amplifier performance

Practical issues are considered to determine if significant improvements in the sensitivity, of 1.55-μm optical receivers can be realized through the use of semiconductor laser preamplifiers. It is found that practical problems related to realizable values of population inversion parameter, input coupling losses, external optical filter requirements, polarization effects, and source laser stability make it unlikely that optical preamplifiers can approach their optimum performance at data rates below several Gbit/s. The most promising application of optical preamplifiers will therefore be to increase the sensitivity of receivers in future fiber optic communication systems operating at multigigabit data rates.     

全光中继光纤传输系统中掺铒光纤放大器监控的研究

文章对全光中继光纤传输系统中掺铒光纤放大器(EDFA)作为提升放大器、线路放大器和前置放大器的监控问题进行了探讨,提出了利用相干光时域反射仪与本地控制单元监测和控制线路EDFA的增益与主备用倒换的方案,该方案可实现对上行和下行的线路EDFA的单端全光监测。     

Use of solid-state devices in noise measurements

For accurate noise measurements the use of valves in preamplifiers has its advantages and disadvantages. Analysis in this paper shows that a combination of the bipolar and unipolar transistors offers a very satisfactory substitute for the valve in low noise preamplifiers for operation over a wide range of source resistances (10ω—1 Mω).     

Low-noise, high-gain Si-bipolar preamplifiers for 10 Gb/soptical-fiber links-design and realization

Design principles and circuit configurations of Si-bipolar transimpedance preamplifiers for 10 Gb/s optical-fiber links are discussed. The target specifications of the amplifier are near the limit achievable by the available technology. Therefore, the different amplifier stages had to be carefully optimized with respect to both flat magnitude and constant group delay of the total transimpedance up to about 7.5 GHz. Two different versions of preamplifiers were fabricated in an advanced production technology (f_T≈23 GHz). High transimpedance (710 Ω) and low equivalent input noise current density (averaged: ≈9 pA/√(Hz)) were achieved     

Reduction of preamplifier noise induced measurement errors in radiometers

A method is described to eliminate measurement errors in a radiometer set-up which are caused by correlation between the input and output noise waves of the preamplifiers in the case of a mismatched object.     

Gigabits-per-second optical interconnection networks:fault-tolerance with and without optical amplifiers

This paper quantifies the power budget concerns with respect to the number of consecutive faults that must be tolerated before a network can fail. In particular, it is shown that multiple consecutive failures may have a serious adverse effect on the speed of gigabit optical networks. Results indicate that, with 20 nodes using simple direct-detection, only passive star networks can operate at Gb/s in the event of multiple consecutive faults. Use of optical preamplifiers is shown to remedy this shortcoming substantially: even with 3 consecutive node failures, optical networks with passive star couplers or single couplers can achieve Gb/s transmission speed for a node spacing of up to 2.3 km     

Practical charge-transfer amplifier design architectures for low-power flash A/D converters

Two improved charge-transfer amplifiers (CTAs), used as zero-static-bias comparator preamplifiers in flash analog-digital converters, are proposed. The first improvement eliminates the capacitive coupling at the amplifier input, reducing area and input capacitance. The second eliminates the need for a common-mode output reference voltage by deriving the common-mode output from a switched average of the power supplies. In the latter, nearly a full-scale input range is achieved while preserving the low-power low offset characteristics of earlier CTAs. Voltage comparator devices were constructed in 0.6-/spl mu/m double-poly, triple-metal CMOS to test the prototype CTA architectures. Input common-mode range and offset performance consistent with simulation data is demonstrated with a 10X reduction in input capacitance. Measured dynamic power dissipation on the order of 3-6 /spl mu/W/MSPS is observed. The experimental CTA preamplifiers occupy roughly 0.015 mm/sup 2/.     

Capacity analysis of MediaGrid: a P2P IPTV platform for fiber to the node (FTTN) networks

This paper studies the conditions under which P2P sharing can increase the capacity of IPTV services over FTTN networks. For a typical FTTN network, our study shows a) P2P sharing is not beneficial when the total traffic in a local video office is low; b) P2P sharing increases the load on FTTN switches and routers in local video offices; c) P2P sharing is the most beneficial when the network bottleneck is experienced in the southbound segment of a local video office (equivalently a northbound segment of an FTTN switch); and d) sharing among all FTTN serving communities is not needed when network congestion problems are solved by using some other technologies such as program pre-caching or replication. Based on the analytical results, design for IPTV services which monitors FTTN network conditions and decides when and how to share videos among peers to maximize the service capacity. Simulations and bounds both validate the potential benefits of the MediaGrid IPTV service platform