测试精品廊

NetTestCMA4000i光测试系统ＮｅｔＴｅｓｔ日前发布了新的ＣＭＡ４０００ｉ光测试系统。ＣＭＡ４０００ｉ为Ｃ -波段和Ｌ-波段的ＤＷＤＭ网络提供一个新的光谱分析仪（ＯＳＡ）模块、一个５０ｄＢ动态范围ＯＴＤＲ模块和简化了多种光纤测试应用的全新测试功能。ＣＭＡ４０００ｉ是测试长距离骨干网或无源光网络（ＰＯＮ）的理想解决方案。基于ＣＭＡ４０００业界领先的长距离（１２０～２５０ｋｍ）测试功能的成功 ,ＣＭＡ４０００ｉ为测试中等距离“城域”网络（４０～１２０ｋｍ）、短距离“最后一公里”网络或ＰＯＮ提供了新的解决方案…     

基于SNSP的呼叫处理模型及其性能分析

本文研究了我们在“无线接入中心交换局系统”（ＷＡＣＯＳ）中提出的基于“简单网络信领协议”（ＳＮＳＰ）的“分布式呼叫处理模型结构”（ＤＣＰＡ）。该结构根据路由状态执行呼叫许可控制（ＲＣＡＣ）,采用“预建立链路”和“并行连接控制”（ＰＣＣ）相结合的“改进的并行连接控制”（ＩＰＣＣ）算法加快呼叫处理进程。分析结果表明,同样的网络条件下〉ＲＣＡＣ更能保证业务尤其是低优先级业务的;ＱｏｓＤＣＰＡ结构更易实现     

无源光网技术分析

文章在描述了无源光网（ｐａｓｉｖｅｏｐｔｉｃａｌｎｅｔｗｏｒｋ）的网络结构后,对ＰＯＮ的几种组网方案（ＴＤＭ／ＴＤＭＡ、ＷＤＭ和ＳＣＭＡ）进行了分析,然后着重从经济的角度分析了ＰＯＮ的器件技术,最后对网络升级策略进行了讨论。     

惠普和掌中万维展示其产品设备及技术解决方案

惠普 ＷＡＰ应用解决包括 ＷＡＰ ＩＮＦＯ服务、ＷＡＰ Ｅ—ｍａｉｌ服务、ＷＡＰ搜索引擎和 ＷＡＰ金融服务。其中ＷＡＰｓｅｒｖ水虎鱼系列解决方案是以实现移动电子化服务为目标的产品,是一系列结合了完整硬件、软件、应用、第三方产品和培训、服务、技术支持的完整的ＷＡＰ 解决方案包。掌中万维目前已形成了支持电信级和企业级的全套无线互联产品：ＭＩＰＴＭ、ＭＡＰＴＭ、ＭＣＳＴＭ、ＭＩＧＴＭ、Ｐ这些产品ＷＡＰ和ＳＭＳ,并均适用于各种网络,如 ＧＳＭ、ＣＤＭＡ、ＧＰＲＳ、３Ｇ、ＦＬＥＸ、ＰＯＣＳＡＧ、ＣＣＰＤ等。同时…     

国外信息

国外信息ＲＴＡ飞秒光参量振荡器采用新型非线性材料ＲｂＴＩＯＡＳＯ４（ＲＴＡ）的高重复率光参量振荡器（ＯＰＯ）在２．１５～３．６５ｕｒｎ（空闪光）波段可调谐，功率高达２００ｍｗ．其他的砷酸氧钛晶体（ＫＴＩＯＡ４Ｏ’和ＣＳＴＩＯＡＳＯ４）已用来验证ＯＰＯ...     

POCSAG编码的差错控制

ＰＯＣＳＡＧ编码在无线通信领域有广泛的应用，本文介绍ＰＯＣＳＡＧ码的结构，重点分析ＰＯＣＡＳＡＧ码的译码和纠错原理。     

GSM网络优化工具COMPASS

ＧＳＭ网络优化工具ＣＯＭＰＡＳＳ是ＧＮＮｅｔｔｅｓｔ专为ＧＳＭ网络优化而设计的功能强大的软件工具 ,利用ＧＮＮｅｔｔｅｓｔ的ＭＰＡ系列多链路协议分析仪在Ａ接口和Ａ -ｂｉｓ接口信令链路上记录的数据进行处理和分析 ,为ＧＳＭ网络运行维护人员提供及时准确的网络性能分析。ＣＯＭＰＡＳＳ产品由四部分软件包组成 ,分别是 :ＧＳＭ呼叫记录（Ａ和Ａ -ｂｉｓ接口）、ＧＳＭ呼叫成功／失败分析（Ａ接口）、ＧＳＭ呼叫统计（Ａ接口）、ＧＳＭ无线小区优化。ＣＯＭ ＰＡＳＳ完成的主要功能有 :(１)无线小区覆盖和质量分析ＭＳ和ＢＴＳ会…     

AlGaAs／InGaAs功率PHEMT用异质材料的计算机优化与器件实验结果

借助一新的工艺模拟与异质器件模型用ＣＡＤ软件──ＰＯＳＥＳ（Ｐｏｉｓｓｏｎ－ＳｃｈｒｏｅｄｉｎｇｅｒＥｑｕａｔｉｏｎＳｏｌｖｅｒ），对以ＡｌＧａＡｓ／ＩｎＧａＡｓ异质结为基础的多种功率ＰＨＥＭＴ异质层结构系统（传统、单层与双层平面掺杂）进行了模拟与比较，确定出优化的双平面掺杂ＡｌＧａＡｓ／ＩｎＧａＡｓ功率ＰＨＥＭＴ异质结构参数，并结合器件几何结构参数的设定进行器件直流与微波特性的计算，用于指导材料生长与器件制造。采用常规的ＨＥＭＴ工艺进行ＡｌＧａＡｓ／ＩｎＧａＡｓ功率ＰＨＥＭＴ的实验研制。对栅长０．８μｍ、总栅宽１．６ｍｍ单胞器件的初步测试结果为：ＩＤｓｓ２５０～４５０ｍＡ／ｍｍ；ｇｍ０２５０～３２０ｍＳ／ｍｍ；Ｖｐ－２．０－２．５Ｖ；ＢＶＤＳ５～１２Ｖ。７ＧＨｚ下可获得最大１．６２Ｗ（功率密度１．０Ｗ／ｍｍ）的功率输出；最大功率附加效率（ＰＡＥ）达４７％。     

Al2O3,Cu,Fe,Si,W的热物理性能

１９８５年，科学技术数据委员会（ＣＯＤＡＴＡ）公布了固体热物理性能研究小组的报告，报告分析适用数据并给出了推荐值：Ａｌ２Ｏ３、Ｃｕ、Ｗ和Ｆｅ的比热，Ｃｕ、Ｓｉ、Ｗ和Ａｌ２Ｏ３的热膨胀，Ｃｕ、Ｆｅ、Ｗ和Ｐｔ的电阻率，Ａｌ、Ｃｕ、Ｆｅ和Ｗ的热导率以及Ｐｂ、Ｃｕ和Ｐｔ的绝对热功率。研究小组组长由Ｙ．Ｓ．Ｔｏｕｌｏｕｋｉａｎ教授担任，直至１９８１年去世后，由Ｍｅｒｒｉｌｌ Ｍｉｎｇｅｓ博士担任。自上述报告     

功率半导体器件的新发展

一、ＭＯＳ型功率半导体器件改变了功率变换技术的面貌一年一度的国际功率半导体讨论会（ＩＳＰＳＤ’９７）今年在德国召开。过去功率半导体器件的国际会议都包含在半导体器件（主要是集成电路，如ＩＥＤＭ会议）或应用技术（如ＰＥＳＣ，ＩＰＥＣ，ＩＡＳ）的会议中，而...     

利用SOA交叉增益调制实现2.5 Gbit/s非归零码的全光波长变换

采用半导体光放大器 (SOA)的交叉增益调制进行了 2 5Gbit/s的非归零码光脉冲的波长变换。向下波长变换间距大于 2 0nm ,向上波长变换间距大于 10nm。对变换信号测量了接收机入纤功率和误码率的关系。实验中采用同向变换的方式 ,信号光中心波长固定 ,探测光采用外腔半导体激光器 ,中心波长连续可调。对变换信号进行了至少 1h的测量 ,误码为零。为其在波分复用(WDM)网络中的应用奠定了基础。     

High-gain 1310-nm reflective semiconductor optical amplifiers with low-gain uncertainty

A 1310-nm reflective semiconductor optical amplifier with a gain uncertainty of only 0.8 dB at an average gain level of over 30 dB has been demonstrated using a microoptic polarization reversing retroreflector. For this amplifier 3-dB saturation output powers of up to 10 dBm and a noise figure of 7.5 dB have been obtained. A low gain uncertainty for undefined input signal polarization states and input signal wavelengths (which may vary over several nanometers) is of primary importance in switching applications.     

基于半导体光放大器交叉增益调制的波长转换的理论分析

本文利用小信号理论模型分析了基于半导体光放大器交叉增益调制的波长转换 ,获得了波长转换效率的解析表达式。结果表明 ,波长转换的频带响应宽度受到光放大器驱动电流、波导中的光功率以及转换波长的影响。     

Experimental linewidth-insensitive coherent analog optical link

We constructed an experimental linewidth-insensitive coherent analog optical link. The transmitter utilizes an external electro-optic amplitude modulator and a semiconductor laser. The receiver consists of a heterodyne front-end, a wideband filter, square law detector and narrowband lowpass filter. We performed experimental measurements and theoretical analyses of the spurious-free dynamic range (SFDR), link gain and noise figure for both the coherent AM and the direct detection links; we investigated the dependencies of the foregoing parameters on the received optical signal power, laser linewidth, IF bandwidth, and the laser relative intensity noise (RIN). By selecting a wide enough bandpass filter, we made the coherent AM link insensitive to laser linewidth. The coherent AM link exhibits a higher SFDR than the corresponding direct detection link when the received optical signal power is less than 85 μW. The noise figure for the coherent link is greater than that for the direct detection link under all conditions investigated. For received optical signal powers greater than 4 μW, the link gain for the direct detection link is greater than that for the coherent AM link. The following are the link parameters that have been achieved for the coherent AM link investigated: SFDR=88 dB·Hz^2/3, link gain=-25 dB and noise figure=78 dB; this performance has been obtained with a received optical signal power of 85 μW, and a local oscillator power at the photodetector of 228 μW. The link performance can be further improved by auxiliary subsystems such as a balanced receiver and impedance matched transmitter and receiver ends; and/or by using better optical and electrical devices like higher power lasers, linearized optical modulators, low-noise and high gain RF amplifiers, and optical amplifiers,     

Transmission performance of chirp-controlled signal by usingsemiconductor optical amplifier

We examine the fiber transmission performance of the optical signal whose chirp is controlled by utilizing phase modulation in semiconductor optical amplifier (SOA) with both simulations and experiments. This chirp control technique converts a positive chirp created by electroabsorption (EA) modulator into negative chirp, which reduces the waveform degradation due to the chromatic dispersion in transmission over standard single-mode fiber (SMF). It also provides an optical gain that is sufficient to compensate the insertion loss of the EA modulator. We investigate how the chirp control is affected by the input power to the SOA and the carrier lifetime of the SOA. As the SOA input power increases, the negative chirp becomes large, while the waveform is largely distorted due to gain saturation. However, the waveform distortion at high SOA input powers can be shaped by using a frequency discriminator. The acceleration of the carrier lifetime also reduces the waveform distortion due to gain saturation. We demonstrate that the chirp control technique is effective even for a high bit rate optical signal up to 10 Gb/s, when the carrier lifetime is expedited by optical pumping     

A comparison of dissipated power and signal-to-noise ratios inelectrical and optical interconnects

A comparison between dissipated power and signal-to-noise ratios (SNR's) in electrical and optical interconnects is performed. It is shown that in the absence of amplification to logic voltage levels the electrical interconnection requires much lower signal powers. However, if the amplification in the receiver is included, comparable total power dissipation and SNR's result under the constraint of equal output voltage     

Longitudinal spatial hole burning and associated nonlinear gain ingain-clamped semiconductor optical amplifiers

The longitudinal spatial hole burning (LSHB) in gain-clamped semiconductor optical amplifiers (GCSOAs) is investigated by means of a numerical model, which is based on position-dependent rate equations for the carrier density and the propagation equations for the optical power. The simulation results show that the carrier densities are nonuniformly distributed within the active layer of GCSOAs. The nonuniformity can be large, especially for high currents and optical signal powers near the saturation. It is found that the LSHB induces a gain nonlinearity, which causes interchannel cross talk when GCSOAs are used in wavelength division multiplexing (WDM) applications. In order to reduce this gain nonlinearity, two methods are analyzed: the use of low resistivity devices and the use of unbalanced Bragg mirror reflectivities     

Pump-to-signal transfer of low-frequency intensity modulation in fiber optical parametric amplifiers

This paper describes the theoretical and experimental investigation of the transfer of low-frequency intensity modulation (IM) from pump to signal in fiber optical parametric amplifiers (OPAs). It is first established that low-frequency IM of the pump remains unchanged over the length of the amplifier in spite of the presence of parametric gain. The pump-power dependence of the OPA gain is then used to calculate the instantaneous effect of pump IM on the signal and idler output powers. These calculations are performed for both one- and two-pump OPAs. The main predictions are that 1) the ratio /spl rho/ of the signal intensity modulation depth to that of the pump varies across the OPA gain spectrum and 2) for a 20-dB gain, /spl rho/ can exceed 10 at some wavelengths, which indicates that this effect can be detrimental. Experiments have been performed to verify these predictions. Using sinusoidal IM of the pump, the resulting amplified signal IM was measured, and the experimental results were found to be in good agreement with the theoretical predictions.     

Comprehensive analysis of two cascaded semiconductor optical amplifiers for all-optical switching operation

This paper presents numerical calculations and experimental results for two cascaded semiconductor optical amplifiers (SOAs) in a counterpropagating configuration for an all-optical switching operation. A detailed theoretical analysis with regard to the gain evolution and the extinction ratio (ER) through the SOAs' cavities show that the two cascaded SOAs have improved performance over the single SOA configuration. A measured ER up to 20 dB is obtained for close contra-directional signal wavelengths and for a wide range of optical input powers. An all-optical switching operation is realized for 2.5-GHz data pulses, and its feasibility is demonstrated with an ER higher than 12 dB over a wide range of wavelength.     

Gain measurements of InGaAsP 1.5 ?m optical amplifiers

We describe the first high-resolution measurements of optical amplifier gain spectra. We demonstrate 1.5 ?m, near-travelling-wave amplifiers with relatively smooth gain spectra and high output powers, and compare them with Fabry-Perot amplifiers.