偏振模色散对高速光码的影响

研究一阶、二阶偏振模色散（PMD）对10 Gb/s和40 Gb/s的光传输系统性能的影响，考虑PMD的统计特性，基于基本偏振态（PSP）理论数值模拟了非归零码（NRZ）和归零码（RZ）在传输过程中产生的脉冲畸变以及系统Q值的变化。结果表明，传输速率越高PMD对系统性能的影响越显著，二阶PMD也将不可忽略。另外，RZ码传输性能明显优于NRZ码并且可通过预啁啾进行改善。     

共沉淀法合成球形正极材料xLi2MnO3·（1-x）Li(Ni1/3Co1/3Mn1/3)O2（x=0.2、0.4、0.6）及其性能研究

以氨水作为络合剂,采用氢氧化物共沉淀法合成了球形富锂锰基正极材料xLi2MnO3·(1-x)Li(Ni1/3Co1/3Mn1/3)O2(x=0.2、0.4和0.6),并对合成的不同组分样品材料的化学成分、结构、形貌和电化学性能进行了表征。结果表明,样品材料的化学组分与其理论含量相同,随着x的增大,材料的粒度变小,在电压范围为2.5~4.6V条件下进行充放电性能测试时,材料的首次充放电容量随着x值减小而增加,且当x=0.2时,材料在不同倍率条件下具有最大的放电容量。     

基于SPW的TPC码建模与仿真

SPW是进行通信系统建模与仿真的开发平台,具有非常强大的用户接口功能。TPC码是近年来出现的高效信道编码技术,具有优越的纠错性能。在研究TPC码编译码理论的基础上,介绍了SPW封装模块的步骤,开发了TPC码编译码模块,并将其嵌入SPW通信库。搭建了基于SPW的性能测试平台,在此基础上进行了计算机仿真。     

无线中继网络系统容量最大化中继选择机制

分析了基于用户频谱效率的中继选择算法的不足,基于最大流最小割定理,给出了系统容量最优化问题模型,分析了两跳中继网络接入链路和中继链路对系统容量的不同影响.基于链路权重因子,提出一种基于系统容量最大化的中继选择算法.对不同中继选择算法下的系统容量差异的理论与仿真分析结果表明,提出的系统容量最大化中继选择算法可以获得更优的系统容量性能,并对网络拓扑和节点个数具有良好的鲁棒性.     

偏振模色散对NRZ码和RZ码的40Gbit/s系统性能影响的仿真分析

偏振模色散(PMD)是进一步提高现有光纤通信系统单信道速率必须克服的障碍之一。本文基于已铺设光纤的典型值,针对偏振模色散对采用NRZ码和RZ码的40Gbit／s光纤通信系统的性能影响进行了分析与仿真。结果表明,考虑PMD的影响时,采用RZ码的系统并不一定比采用NRZ码的系统的传输性能好,而在占空比[0,1]之间存在一个最佳值,此时,高速系统受偏振模色散的影响最小。这对于研究、设计高速光纤通信系统时选择合适的码型和RZ码的占空比,具有重要的参考意义。     

P(VdF-HFP)-PMMA聚合物电解质的研究

采用共混法制备了P(VdF-HFP)-PMMA聚合物电解质，PMMA与电解液有更好的相溶性。含PMMA45%的聚合物膜，20℃时电解液吸附量为260%，离子导电率为0.95mS/cm。以该膜和1mol/L LiPF6(EC/EMC)为电解质，LiCoO2为正极，碳纤维为负极的聚合物锂离子电池具有较小的界面电阻和电荷转移电阻，良好的循环稳定性（1/3C倍率循环35次，95%初始放电容量），和良好的倍率性能（2C倍率，73%初始放电容量）。     

浅析嵌入式工业控制系统中的人机交互系统技术实现

些年来,工业过程控制的智能化需求,3G（消费电子、计算机、通信）产品、信息家电的推陈出新。全球互联网的飞速发展等等,都为嵌入式系统提供了非常广阔的应用空间。作为人机交互技术的重要内容之一的图形用户界面（GUI）,通过丰富的图形图像信息、直观的表达方式与用户交互。本文针对工业控制领域中对嵌入式的特殊性能要求。首先在深入分析了多种主流嵌入式GUI系统体系结构和实现原理的基础上,分析了一种基于多线程处理的GUI系统的设计思想。     

一种大容量的二维光正交码

首先构造一种扩展的立方线性同余码（ECLC）并分析了其码字性能。在此基础上，用该码作为时间扩频伪随机序列和以素数码（PC）作为跳波长伪随机序列。再构成一种新的二维光正交码ECLC/PC，然后分析了ECLC/PC码字的性能，并与EQC/PC作为比较，相比之下，两者的码长和码重都相等，前者的互相关性能略有下降。但码字容量大大增加。因此，ECLC/PC适合于接入用户数较多的OCDMA系统。     

活性碳吸附Au（CN）2^—机理研究

本文研究了椰壳炭,煤质炭吸附Au(CN)_2~-的性能,首次发现煤质炭比表面低于椰壳炭,其平衡吸附Au(CN)_2~-容量高于椰壳炭;用傅利叶变换漫反射红外光谱测定了活性炭化学结构;研究结果表明Au(ON)_2~-在活性炭上吸附是络合吸附,与活性炭芳环缩聚程度有关,芳环缩聚程度高,吸附Au(ON)_2~-容量大     

尿素改性对钠离子电池负极材料NaTi_2(PO_4)_3电化学性能的影响

为提高水溶液钠离子电池负极材料NaTi_2(PO_4)_3(NTP)的导电性和倍率性能,以尿素(CO(NH_2)_2)为碳源采用溶剂热法合成了CO(NH_2)_2/NaTi_2(PO_4)_3(C/NTP)复合负极材料。采用XRD、SEM、TEM、Raman和恒流充放电等手段分析了材料的结构、C/NTP形貌和电化学性能。研究了不同阶段升温速率对C含量、包覆层石墨化程度及对电化学性能的影响。实验结果表明,低于400℃升温速率越小,C/NTP残碳量越高;400~650℃之间升温速率越小,包覆层石墨化程度越高,并提高了其电化学性能;在5C倍率下2℃/min热处理的样品首圈放电比容量为114.9mAh·g~(-1),循环30次后容量保持在91.9mAh·g~(-1);10C下放电比容量为87mAh·g~(-1),20C下放电比容量仍保持在71mAh·g~(-1),展现出高倍率下优异的循环性能。     

抑制OFDM信号峰均比对直接检测光传输系统的性能影响

高峰均比是OFDM通信系统的主要缺点之一,光OFDM通信系统也存在同样的问题.本文将联合Hadamard变换和限幅(Clipping)方法抑制峰均功率比算法成功应用到直接检测的光正交频分复用光纤传输实验平台,重点研究了算法对系统误码性能的影响.实验中产生的2.5 Gb/s QPSK OFDM光信号在标准单模光纤中传输1...     

可溶性聚噻吩甲烷的制备与光学性能

利用噻吩和对二甲氨基苯甲醛在酸性条件下共聚,制备了一种具有可溶性、分子链部分共轭的聚噻吩甲烷衍生物。采用傅里叶变换红外光谱、紫外-可见吸收光谱、荧光光谱、热重分析和X射线衍射谱对聚合物的分子结构、光学性能、热稳定性能及聚集态结构进行了表征和分析。由紫外-可见吸收光谱可得,该聚合物的光学禁带宽度为1.3 eV,属于窄带隙聚合物。荧光光谱显示,该聚合物溶液在480 nm可见光的激发下,出现约600 nm的发射光,说明该聚合物为橙黄色的荧光材料。X射线衍射谱中17.3°附近存在1个较为尖锐的衍射峰,表明该聚合物聚集态结构为部分结晶态。     

Convenient near-field optical measurement and analysis of polystyrene spheres

The modification of a commercial tapping mode atomic force microscope (AFM) into a transmission mode near-field scanning optical microscope (NSOM) is presented and polystyrene spheres in the diameter of 100 nm are used in this experiment. The detection of near-field signals is based on photodiodes with lock-in technique, and resolutions of topography and near-field signals obtained are about 10 and 20 nm, respectively. Furthermore, it is discovered that the computer-simulated near-field energy distribution profile, obtained by scanning over polystyrene spheres under illumination mode, falls within 5% range as compared with experimental values. The near-field absorption coefficient can be determined by this way. This will be a useful theoretical model to analyze the near-field transmission effect from others.     

High Performance and Stable All‐Inorganic Metal Halide Perovskite‐Based Photodetectors for Optical Communication Applications

Photodetectors are critical parts of an optical communication system for achieving efficient photoelectronic conversion of signals, and the response speed directly determines the bandwidth of the whole system. Metal halide perovskites, an emerging class of low‐cost solution‐processed semiconductors, exhibiting strong optical absorption, low trap states, and high carrier mobility, are widely investigated in photodetection applications. Herein, through optimizing the device engineering and film quality, high‐performance photodetectors based on all‐inorganic cesium lead halide perovskite (CsPbI_xBr_3–x), which simultaneously possess high sensitivity and fast response, are demonstrated. The optimized devices processed from CsPbIBr₂ perovskite show a practically measured detectable limit of about 21.5 pW cm^?2 and a fast response time of 20 ns, which are both among the highest reported device performance of perovskite‐based photodetectors. Moreover, the photodetectors exhibit outstanding long‐term environmental stability, with negligible degradation of the photoresponse property after 2000 h under ambient conditions. In addition, the resulting perovskite photodetector is successfully integrated into an optical communication system and its applications as an optical signal receiver on transmitting text and audio signals is demonstrated. The results suggest that all‐inorganic metal halide perovskite‐based photodetectors have great application potential for optical communication.     

Exact error rate analysis of free-space optical communications with spatial diversity over Gamma–Gamma atmospheric turbulence

The error rate performances and outage probabilities of free-space optical (FSO) communications with spatial diversity are studied for Gamma–Gamma turbulent environments. Equal gain combining (EGC) and selection combining (SC) diversity are considered as practical schemes to mitigate turbulence. The exact bit-error rate (BER) expression and outage probability are derived for direct detection EGC multiple aperture receiver system. BER performances and outage probabilities are analyzed and compared for different number of sub-apertures each having aperture area A with EGC and SC techniques. BER performances and outage probabilities of a single monolithic aperture and multiple aperture receiver system with the same total aperture area are compared under thermal-noise-limited and background-noise-limited conditions. It is shown that multiple aperture receiver system can greatly improve the system communication performances. And these analytical tools are useful in providing highly accurate error rate estimation for FSO communication systems.     

Comparative performance study of one or multiple receivers schemes for FSO links over gamma–gamma turbulence channels

Terrestrial free space optical telecommunication systems offer license-free very high bandwidth access characteristics with significantly low installation and operational cost. On the other hand, the performance of such a system depends strongly on the weather conditions in the area between the transmitter and the receiver due to the fact that the transmission media is the atmosphere. A very significant phenomenon which decreases a FSO links' performance is atmospheric turbulence. In order to counterbalance this reduction, in this work, we consider a free space optical system with a multiple receivers' scheme and diversity in space that operates under weak to strong atmospheric turbulence conditions modeled by the gamma–gamma distribution. We derive closed form mathematical expressions for the estimation of the outage probability and the average bit error rate of the multiple receivers' system. Additionally, we compare the performance capabilities of the single point to point link with those of the spatial diversity scheme under the assumption that the total aperture surface of the receivers of the latter is the same as the aperture surface of the single receiver of the former. Moreover, we demonstrate numerical results for a variety of common practical cases for both cases, with and without, spatial diversity.     

基于光纤光栅的波分复用系统设计

设计了两种基于光纤布拉格光栅的波分复用(WDM)系统,一种为基于光纤光栅的四路波分复用系统,另一种为结合光分插复用器(OADM)的四路波分复用系统。给出了基于Opti System的波分复用光传输系统仿真模型,对复用及解复用后的光信号进行仿真得出了光谱图,对传输性能及Q因子、误码率、眼图等参数进行分析。在第二种结构中光纤光栅作为色散补偿器、光反射器和滤波器使用,可以实现任一波长的上载和下路。两种波分复用系统眼图张开良好,误码率均低于10e-9。证明了波分复用系统的正确性和设计方案的可行性。     

空间光通信系统的设计及实现

提出一种较全面的空间光通信系统结构。该系统的光发射接收子系统采用三发三收的设计方法,以增大光的发射功率和接收功率;APT子系统采用望远镜进行粗瞄准,音频调制光标信号进行精瞄准;控制子系统采用Ethernet接口,远程通过Internet对系统进行测量和控制的设计方法。给出一个近地大气空间光通信系统的设计实例, 其信号传输速率为155Mbps,传输距离为4km,在误码率不大于10-9条件下,系统接收灵敏度达到-52dBm。