Channel Pre-emphasis Equalization for a 270 km 40×40 Gbit/s WDM System with Cascaded EDFAs/Raman Amplifiers

Optical channel pre-emphasis equalization is experimentally researched for a 270 km 40 × 40 Gbit/s wavelength division multiplexing （WDM） transmission system with three Erbium-doped fiber amplifiers （ED- FAs） and Raman amplifiers concatenated as booster amplifier. The channel imbalance of the overall system changes with different sets of power launched into EDFAs. By appropriately choosing the power input to concatenated EDFAs, the output spectrum of 40 channel signal can be equalized to the most extent. The merit of benefit can be around 5.5 dB by this pre-emphasis equalization. The requirement for the gain equalizer is therefore greatly released. Then the gain imbalance of the overall system and the power imbalance of 40 channels are compared and the two almost matches, but the significant difference lies on some channels. Finally, the pump power into Raman amplifier is also optimized, and another 1.3 dB improvement of channel equaliza- tion can be further achieved.     

AutoCAD中表面粗糙度和形位公差模块的开发

本文主要介绍了利用ＡｕｔｏＬＩＳＰ语言对ＡｕｔｏＣＡＤ进行二次开发，增加其形位公差，表面粗糙度等标注功能，并在标注方式上采用图标菜单的方法。     

非线性偏振旋转锁模光纤激光器数值模型

利用二能级Giles模型来计算掺铒光纤增益,并通过琼斯矩阵描述偏振控制器,提出了一种基于非线性薛定谔方程的非线性偏振旋转锁模光纤激光器的数值模型。该模型具有物理意义更加清晰、便于分析泵浦功率对锁模影响的优点。采用1.0 m长的掺铒光纤、5.8 m长的单模光纤和85:15的输出耦合器,当泵浦功率为25 mW时数值计算得到均方根宽度为0.30 ps的超短脉冲。研究了泵浦功率对锁模脉冲波形和光谱的影响,并讨论了泵浦功率与掺铒光纤中增益分布的关系。通过实验得到了锁模脉冲,其光谱形状与仿真得到的结果相似。测量了不同泵浦功率下脉冲的平均功率,变化趋势也与理论值吻合。     

Multiple-impairment monitoring for optical duobinary system based on delay-tap asynchronous sampling

A technique using artificial neural networks trained with parameters derived from delay tap plots for optical performance monitoring in 40 Gbit/s duobinary system is demonstrated. Firstly, the optical signal is delay tap sampled to obtain two-dimensional histogram, known as delay tap plots. Secondly, the features of delay tap plots are extracted to train the feed forward, three-layer preceptor structure artificial neural networks. Finally, the outputs of trained neural network are used to monitor optical duobinary signal impairments. Simulation of optical signal noise ratio (OSNR), chromatic dispersion (CD), and differential group delay (DGD) monitoring in 40 Gbit/s optical duobinary system is presented. The proposed monitoring scheme can accurately identify simultaneous impairments without requiring synchronous sampling or data clock recovery. The proposed technique is simple, cost-effective and suitable for in-service distributed OPM.     

石墨烯被动锁模光纤激光器的研究进展

自2009年石墨烯(Graphene)材料被成功用于产生超短脉冲以来,出现了多种腔形、多种波长、多种脉冲特性的锁模激光器。利用石墨烯可饱和吸收特性制成的锁模器件具有稳定性好、响应波长广、恢复时间短、插入损耗小等多方面的优势,是目前超短脉冲领域的研究热点。重点对石墨烯被动锁模光纤激光器的研究进展进行了总结,并针对该领域面临的问题,指出其发展趋势。     

10Gbit/s色散补偿系统中自相位调制效应的研究

首先讨论了单模光纤中自相位调制对系统色散的影响。数值计算和实验结果表明。增加入纤功率能在一定程度上抑制色散效应 ,当入纤功率为 1 5dBm时 ,对于 4 0 .0km的单模光纤 ,自相位调制效应和色散恰好抵消 ,功率代价接近为零。然后比较了前、后置色散补偿系统的性能。理论分析和实验表明 ,在入纤光功率较大的情况下 ,采取前置、完全色散补偿系统具有较低的误码率。前置补偿最佳入纤功率比后置补偿最佳入纤功率高约 1 0 .0dB。这表明 ,采取前置、完全色散补偿 ,系统具有较长的中继距离和较高的接收端光信噪比 ,对 (1 6 0× 1 0Gbit/s)DWDM系统 30 0 0km超长距离传输中光放大和色散补偿问题的整体优化具有重要现实意义。     

D型石墨灰铸铁气缸的金属型重力铸造

介绍气缸金属型重力铸造工艺设计的经验,针对生产中发生的缩孔、缩松、渣孔、气孔缺陷制定合理的控制措施.采用水冷金属型铸造,并加入合金元素增大铁液过冷倾向,获得D型石墨铸铁,用以生产空调器压缩机气缸,其金相组织和性能均达到技术要求.     

塑料壳体注射压缩成型工艺及模具

介绍了一种塑料壳体的成型工艺———塑料注射、压缩复合成型工艺,并设计了实现该成型工艺的模具。由于纤维取向、去除飞边和流道料损失等是热固性塑料加工中影响成本的主要问题,故着重介绍了降低上述费用的办法。     

高等教育考核方式改革初探

高等教育考核方式在高等教育教学中占有重要地位。传统的高等教育考核方式逐渐显出弊端,不利于考察学生的创新能力、自主学习能力。分析高等教育考核方式的现状,探索值得借鉴的国外高等教育考核方式及高等教育考核方式改革的具体措施。