A novel design for single-polarization single-mode photonic crystal fiber at 1550 nm

The present paper proposes a novel design for achieving single-polarization single-mode (SPSM) operation at 1550 nm in photonic crystal fiber (PCF), using a rectangular-lattice PCF with two lines of three central air holes enlarged. The proposed PCF composed entirely of silica material is modeled by a full-vector finite element method with anisotropic perfectly matched layers. Simulations show that single-polarization operation within broad wavelength range can be easily realized with the proposed structure. The wideband SPSM operation features, the low confinement losses, and the small effective mode area are the main advantages of the proposed PCF structure. A SPSM-PCF with confinement loss less than 0.1 dB/km within wavelength range from 1370 to 1610 nm and effective mode area about 4.7μm2 at 1550 nm is numerically demonstrated.     

针对WWW业务的光缓存优化设计

研究了异步光分组网中的输出光缓存问题，与以往不同的是在处理光分组到达时间间隔时采用Weibull分布，以便更有效地描述互联网中的WWW业务流量类型．通过建立基于Weibull分布的排队模型，得到了排队模型中的丢包率的解析式，并根据数值解得出了光缓存系统的丢包率、系统实际利用率、服务窗口利用率以及平均排队时间随光纤延时线单位缓存时间变化的关系曲线．研究结果表明：在不同的业务强度和缓存深度下选取恰当的单位缓存时间，可以优化光缓存系统的性能．     

NOLM-based wavelength conversion with FBG band-pass filter for optical packet switching

Nonlinear-optical-loop-mirror wavelength conversion is studied in details. A set of two-phase-shiftedBragg gratings are introduced into the coverter,serving as a narrow band-pass filter to remove newfrequencies generated by walk-off and to compensate the dispersion. Numerical simulations are performedto validate our method. The results show that the converted pulses after the filter are reshaped and,sometimes, even compressed.     

基于UVC LED的小型化紫外无线通信技术

紫外光通信技术具有低窃听、低位辨、全方位、全天候、抗干扰等优点,而基于紫外光灯的通信系统存在光源体积大、易碎、调制困难、通信速率低、功耗大等问题。设计了一种基于紫外C波段(UVC)LED的小型化无线通信系统方案,并对系统性能进行了理论分析。系统光源采用UVC LED,探测器采用日盲光电倍增管(PMT)和窄带紫外滤光片,通信系统采用开关键控(OOK)和脉冲位置调制(PPM)调制方案。仿真结果表明所设计的紫外无线通信系统可在200mW发射光功率情况下实现直径200m范围内的非视距语音通信和100mW发射光功率情况下实现250m的64Kbps准视距通信。     

Design and analysis of flexible colorless remote node using RSOA-assisted Michelson interferometer

A scheme of flexible colorless remote note with reflective semiconductor optical amplifier (RSOA) assisted Michelson interferometer is proposed. This is capable of generating an optical carrier suppressed signal at a specific radio frequency to suppress the penalty brought about by Rayleigh backscattering and reflection in a full-duplex single fiber transmission network. Simulations are conducted, and the validation of the proposal is discussed by observing the penalty eye opening factor. The results are us...     

Fine-tuning the thicknesses of organic layers to realize high-efficiency and long-lifetime blue organic light-emitting diodes

By using p-bis(p-N,N-diphenyl-aminostyryl)benzene doped 2-tert-butyl-9,10-bis-β-naphthyl)-anthracene as an emitting layer,we fabricate a high-efficiency and long-lifetime blue organic light emitting diode with a maximum external quantum efficiency of 6.19% and a stable lifetime at a high initial current density of 0.0375 A/cm2.We demonstrate that the change in the thicknesses of organic layers affects the operating voltage and luminous efficiency greater than the lifetime.The lifetime being independent of thickness is beneficial in achieving high-quality full-colour display devices and white lighting sources with multi-emitters.     

Characterization of the radiation from single-walled zig-zag carbon nanotubes at terahertz range

This paper investigates the radiation characteristics of metal single-walled zig-zag carbon nanotubes as a dipole antenna at terahertz wave range. The current distribution, input impedance and mutual impedance are calculated for various geometrical parameters of vertically-aligned carbon nanotubes. The numerical results demonstrate the properties of the antenna depending strongly on the geometrical parameters such as the radius, the lengths of carbon nantobues, and the spacing between nanotubes. It is found that the zig-zag carbon nanotubes exhibit very high input impedance and the mutual impedances for antenna array applications. These unique high impedance properties are different from the conventional metal thin wire antenna. The far-field patterns and gain of antenna array are also calculated. The maximum gain of array of 100-element array is up to 20.0~dB, which is larger than the gain of 0.598~dB of single dipole antenna at distance d = 0.5\lambda .     

自相似业务下光缓存设计

提出了在数据包长可变的自相似业务下研究光纤延时线所组成的光缓存问题的解析模型.利用Pareto到达过程来模拟自相似业务.研究表明,缓存深度越大,包丢失率越低,而且存在与业务强度对应的最佳光纤延时线单位,使得在给定的缓存深度下,数据包丢失率最小,在业务强度和缓存深度相同时,Pareto到达比Poisson到达有更大的包丢失率.     

Composite Scattering from the Electrically Very Large Ship-Sea Model Using the Hybrid High-Frequency Method

A hybrid high-frequency method is proposed to analyze the bistatic electromagnetic scattering of the ship target on a very large two-dimensional randomly rough sea surface. The scattering of the ship-sea model is evaluated with the method of equivalent currents （MEC）. The iterative physical optics method （IPO） is utilized to study the electromagnetic coupling effect caused by the hull and rough surface. The shadowing correction based on the Z-Buffer technology is introduced to eliminate the effects of the irrelevant scattering resources. The validity of the hybrid method is confirmed by the SAR simulation results and the scattering property of the ship-sea model is discussed.     

正N边形柱的隐身条件的严格推导及其隐身特性验证

基于坐标变换理论,提出并推导了正N边形柱的隐身条件,并得到了相应隐身罩材料本构参数张量的通解表达式. 根据导出的本构参数张量,利用电磁仿真软件分别对N取不同值时的三个典型算例进行仿真验证. 仿真结果证实了所得到的本构参数张量的正确性. 考虑到损耗对于隐身效果的影响分析,这些分析结果为隐身物理机理的进一步理解,以及降低对称度隐身罩的设计奠定了理论基础. 关键词： 坐标变换 非均匀各向异性介质 本构参数张量 隐身