Nonpolar a-plane light-emitting diode with an in-situ SiNx interlayer on r-plane sapphire grown by metal-organic chemical vapour deposition

We report on the growth and fabrication of nonpolar a-plane light emitting diodes with an in-situ SiN_x interlayer grown between the undoped a-plane GaN buffer and Si-doped GaN layer. X-ray diffraction shows that the crystalline quality of the GaN buffer layer is greatly improved with the introduction of the SiN_x interlayer. The electrical properties are also improved. For example, electron mobility and sheet resistance are reduced from high resistance to 31.6 cm²/(V·s) and 460 Ω/口 respectively. Owing to the significant effect of the SiN_x interlayer, a-plane LEDs are realized. Electroluminescence of a nonpolar a-plane light-emitting diode with a wavelength of 488nm is demonstrated. The emission peak remains constant when the injection current increases to over 20 mA.     

Er/Yb共掺光纤放大器前向放大自发辐射模型

提出了Er/Yb共掺的光纤放大器中,Yb离子仍然存在基态能级斯塔克(Stark)分裂的假设,考虑1060 nm波段辐射,利用速率方程和传输方程,结合Er/Yb共掺双包层光纤的吸收和发射系数谱,采用4阶龙格-库塔(Runge- Kutta)算法,建立了模拟Er/Yb共掺双包层光纤放大器放大自发辐射(ASE)光谱的理论模型。通过改变抽运功率和信号功率,对其前向放大自发辐射光谱特性进行了全面的分析。大信号入射时,改变抽运功率,只改变输出功率大小。输出光谱形状不变,而当信号功率足够小时,前向放大自发辐射光谱在1535 nm和1543 nm处会出现2个局部峰值,理论模拟与实验数据相符。     

基于Bootstrap技术的Web服务QoS值的置信区间估计和预测

目前对Web服务QoS（Quality of Service）的预测研究,通常预测QoS的静态值,很少预测QoS值的置信区间.本文借助非参数统计学的Bootstrap技术,提出估计Web服务QoS值置信区间的方法;然后利用与当前Web用户相似的其他Web用户调用待预测Web服务的QoS历史数据,预测当前Web用户调用待预测Web服务的QoS值的置信区间.本文估计了WSDream数据集1中每个用户调用每个Web服务的QoS值的置信区间,实验发现这些置信区间的上下限近似服从重尾分布.通过随机选择WSDream数据集1中60%到90%的用户和Web服务作为训练集,预测另外10%到40%的用户和Web服务的QoS值,实验结果表明预测的QoS置信区间与估计的QoS置信区间的平均覆盖率超过70%,最高达76%.在服务选择或服务推荐时给用户提供一个估计的或预测的QoS置信区间,可以更好地满足用户的个性化需求.     

Microstructure and optoelectronic properties of gallium- titanium-zinc oxide thin films deposited by magnetron sputtering

Gallium-titanium-zinc oxide(GTZO) transparent conducting oxide(TCO) thin films were deposited on glass substrates by radio frequency magnetron sputtering. The dependences of the microstructure and optoelectronic properties of GTZO thin films on Ar gas pressure were observed. The X-ray diffraction(XRD) and scanning electron microscopy(SEM) results show that all the deposited films are polycrystalline with a hexagonal structure and have a preferred orientation along the c-axis perpendicular to the substrate. With the increment of Ar gas pressure, the microstructure and optoelectronic properties of GTZO thin films will be changed. When Ar gas pressure is 0.4 Pa, the deposited films possess the best crystal quality and optoelectronic properties.     

DWDM用增益平坦EDFA研究

本文阐述了ＤＷＤＭ系统对ＥＤＦＡ的要求和ＥＤＦＡ为达到这些要求的几种实现方法。并给出了ＤＷＤＭ用ＥＤＦＡ级联和增益锁定的实验结果。     

WRI EDFA的特点

本文介绍了ＥＤＦＡ 的应用和发展方向,以及ＷＲＩＥＤＦＡ 的特点。     

具备交叉连接特点的PDH灵活接入终端的模块设计

实现ITU－TG．797建议的PDH灵活接入系统的关键是如何构造灵活接入终端，笔者提出了一整套构成灵活接入终端的、具备交叉连接特点的模块设计方案。     

FTTH用高功率光纤放大器

近年来在Cabie Modem和xDSL等多种形式的宽带接入蓬勃发展的同时，光纤到户也逐渐成为了人们极感兴趣的一种接入方式。光纤到户后，最终将实现电话、有线电视和上网“三网合一”，上网的数据传输速率可以超过100Mb/s比常用的拨号上网速度快200倍以上．将使用户能在家里欣赏高清晰的电视电影，实现快捷的网上办公等，