共查询到20条相似文献,搜索用时 62 毫秒
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分析了湍流大气光传输特性,讨论了光信号闪烁对宽带光无线通信误码率的影响及解决方案。从湍流大气的经典功率谱模型与修正功率谱模型出发,分析了Rytov指数与光场波长的变化关系,讨论了其对传输光场强度起伏的影响,以及分别在球面波与平面波时的差异。从实验上模拟考察了湍流大气对宽带光通信的影响,提出了一种新的从光链路上矫正波前畸变、减弱信号闪烁进而降低通信系统误码率的技术方案。该方案基于遗传算法和无模型盲优化的方式,以Zernike多项式系数为向量,对波前畸变进行编码,根据畸变波前的Zernike多项式的系数实现波前重构。其特点是没有预先测量波前相位畸变信息,而是采用施特列耳比作为遗传算法的适应度评判标准,通过优化达到最佳的波前畸变补偿效果。分析结果表明,该方案对中等强度以下的湍流大气光传输具有明显改善效果。 相似文献
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为了提高传统随机并行梯度下降 (Stochastic Parallel Gradient Descent, SPGD) 算法校正波前畸变的性能,提出了一种基于AdaBelief优化器的新型SPGD优化算法。该算法将深度学习中AdaBelief优化器的一阶动量和二阶动量集成到SPGD算法中以提高算法的收敛速度,并使得算法能够自适应地调整增益系数。 此外,对实际增益系数进行自适应动态裁剪以避免因实际增益系数出现极端值而造成的震荡。仿真结果表明:在37单元变形镜 (Deformable Mirror, DM)下,新型SPGD优化算法能够对不同湍流强度下的波前畸变实现有效校正,不同波前畸变经过校正后的斯特列尔比(Strehl ratio, SR)分别提升至0.83、0.47和0.31。此外,该算法在不同湍流强度下的SR仅仅需要149、229和230次迭代达到阈值,与传统SPGD算法及其他优化算法相比有更快的收敛速度,且在稳定性和参数调节方面也具有一定的优越性。 相似文献
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《中国激光》2015,(12)
在波前校正过程中,变形镜(DM)在强激光连续辐照(CW)下会产生热形变,进而对入射光引入附加波前畸变,从而制约了变形镜的波前校正效果,致使光束质量改善效果变差。从变形镜热形变面形的Zernike多项式分解出发,建立了强激光连续辐照下变形镜的热形变预估模型,根据预估所得的热形变面形,模拟计算得到了变形镜的驱动器控制信号参数,进而驱动变形镜对其自身的热形变面形进行了实时补偿。仿真结果表明,该自校正方法能有效补偿变形镜自身的热形变面形,减小变形镜热形变对其校正能力的影响;采用局部换热方式只能在一定程度上减小变形镜形变面形引起的平移相差和离焦相差,对光束质量的改善效果也比较有限,而该自校正方法能有效减小热形变引起的光程差,从而对光束质量起到明显的改善作用。 相似文献
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基于MEMS技术的分立式微变形镜校正能力研究 总被引:1,自引:0,他引:1
针对基于微型机电系统技术的分立式微变形镜,从镜面面形特点出发分析了方形和蜂窝形阵列变形镜适配能力,并利用ZEMAX软件建立畸变波前和变形镜模型,仿真分析两种分立式微变形镜的校正能力.研究表明在近似子单元数情况下,蜂窝形阵列微变形镜对畸变波前的校正能力更好. 相似文献
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Michael Reilly 《半导体技术》2004,29(12)
DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system. 相似文献
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Thomas M.Trexler 《半导体技术》2004,29(5)
From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test. 相似文献
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The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation. 相似文献
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The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high. 相似文献
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Today, micro-system technology and the development of new MEMS (Micro-Electro-Mechanical Systems) are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible. 相似文献
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Qi-jiang Ran Pei-de Han Yu-jun Quan Li-peng Gao Fan-ping Zeng Chun-hua Zhao 《光电子快报》2008,4(4):239-242
This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel's. 相似文献
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Teleportation of an arbitrary unknown N-qubit entangled state under the controlling of M controllers
A new quantum protocol to teleport an arbitrary unknown N-qubit entangled state from a sender to a fixed receiver under M controllers(M < N) is proposed. The quantum resources required are M non-maximally entangled Greenberger-Home-Zeilinger (GHZ) state and N-M non-maximally entangled Einstein-Podolsky-Rosen (EPR) pairs. The sender performs N generalized Bell-state measurements on the 2N particles. Controllers take M single-particle measurement along x-axis, and the receiver needs to introduce one auxiliary two-level particle to extract quantum information probabilistically with the fidelity unit if controllers cooperate with it. 相似文献
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A continuous-wave (CW) 457 nm blue laser operating at the power of 4.2 W is demonstrated by using a fiber coupled laser diode module pumped Nd: YVO4 and using LBO as the intra-cavity SHG crystal With the optimization of laser cavity and crystal parameters, the laser operates at a very high efficiency. When the pumping power is about 31 W, the output at 457nm reaches 4.2 W, and the optical to optical conversion efficiency is about 13.5% accordingly. The stability of the out putpower is better than 1.2% for 8 h continuously working. 相似文献
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It is well known that adding more antennas at the transmitter or at the receiver may offer larger channel capacity in the multiple-input multiple-output(MIMO) communication systems. In this letter, a simple proof is presented for the fact that the channel capacity increases with an increase in the number of receiving antennas. The proof is based on the famous capacity formula of Foschini and Gans with matrix theory. 相似文献
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《中国通信》2014,(7)
正Wireless Body-area Networks The last decade has witnessed the convergence of three giant worlds:electronics,computer science and telecommunications.The next decade should follow this convergence in most of our activities with the generalization of sensor networks.In particular with the progress in medicine,people live longer and the aging of population will push the development of wireless personal networks 相似文献