共查询到18条相似文献,搜索用时 140 毫秒
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研究了电吸收调制器(EAM) 的衰减随外加反向电压增加而指数增加的情形下,短脉冲光源的脉冲输出和解复用器的开关窗口对EAM 的消光效率、反向DC 偏置电压以及正弦RF 驱动信号的幅度等参量的依赖关系- 在基于EAM 的短脉冲光源中,输出脉冲的消光比等于EAM 消光效率η与正弦驱动电压峰峰值Vpp 的乘积,输出光脉冲的消光比和脉宽均与EAM 的反向偏置电压无关,但输出脉冲的峰值功率与η、Vpp 和Vb 都有关系- 在基于EAM的解复用器中,为了使解复用器的开关窗口近似为矩形,可利用EAM 的削波效应,使Vpp/2> Vb- 在EAM 的消光效率η已知时,通过仔细设计反向DC 偏置电压Vb 和正弦驱动电压的峰峰值Vpp ,达到OTDM 解复用器所需要的开关窗口形状、宽度和消光比- 相似文献
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基于电吸收调制器的解复用器窗口特性分析及优化 总被引:1,自引:1,他引:0
数值模拟了基于电吸收调制器 (Electro absorptionmodulator,EAM)解复用器的开关窗口特性 ,在考虑邻道串扰和强度抖动 (由同步偏离和时间抖动导致 )的光时分复用数值模型中对解复用信号的误码率进行分析。数值模拟结果表明 ,电吸收调制器的窗口特性 (消光比和窗口宽度 )满足 4× 10Gb/s的光时分复用通信系统中解复用器的要求 ;在小的偏置电压下 ,邻道串扰和解复用器的透过率特性必须仔细考虑以达到最小的误码率 ;在大的偏置电压下 ,较大的射频幅度将会使解复用信号误码率最小 相似文献
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利用BS方法讨论了ηc→VV(包括ηc→ρρ,KK,φφ)问题,着重分析了夸克的组份质量和横动量效应对衰变振幅的影响.发现ηc→VLVT被严格禁戒.夸克横动量对增加衰变率有明显效应,但即使考虑了这些因素,理论值仍然比实验值小. 相似文献
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基于电吸收调制晶体(EAM)的超短光脉冲特性研究 总被引:4,自引:1,他引:3
数值模拟了两种形式的基于电吸收调制晶体(EAM)的超短光脉冲源(单EAM)和级联EAM形式)的输出脉冲宽度及消光比与外加反向偏压、射频信号幅度之间的变化关系.数值模拟结果表明,在重复率为10GHz情况下,对于单EAM形式,可以获得的最小脉宽大约为13ps,其消光比大于20dB,脉冲波型接近sech2孤子波型;对于级联EAM形式,我们得到了小于5ps的超短脉冲,消光比也较单EAM形式有较大的提高.因此,单EAM形式的超短脉冲源可以满足20Gb/s的OTDM系统需求,也同样适合于超长距离的光孤子通信系统;级联形式EAM可以满足40Gb/s的OTDM系统光源需求. 相似文献
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燃料电池系统的最大电效率(ηemax)对理解和发展燃料电池技术至关重要.本文通过对燃料电池系统的热力学分析,在考虑加热燃料与空气至燃料电池工作温度的热量需求的基础上,建立了燃料电池运行过程的能量平衡关系,进而推导出了ηemax的显式理论表达式.结果表明,与卡诺效率不同,ηemax与燃料有关.由于除氢燃料外,计算ηemax需要进行化学平衡计算,本文推导了烷烃燃料化学平衡态的解析解.所得理论模型被用于分析温度(T)与燃料水含量及废热回收率对ηemax的影响.结果表明,甲烷和丙烷燃料的ηemax随温度的升高而显著降低.此外,对中等废热回收率且运行于700 ℃≤T≤900 ℃的燃料电池系统,氢气燃料的ηemax要高于甲烷和丙烷燃料的ηemax. 相似文献
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应用群论及原子分子反应静力学方法推导了SiO2分子的电子态及其离解极限,采用B3P86方法,在6-311G**水平上,优化出SiO2基态分子稳定构型为单重态的C2V构型,其平衡核间距Re=RSi—O=0.1587 nm,∠OSiO=111.2°,能量为-440.4392 a.u..同时计算出基态的简正振动频率:对称伸缩振动频率ν(B2)=945.4cm-1,弯曲振动频率ν(A1)=273.5 cm-1和反对称伸缩振动频率ν(A1)=1362.9cm-1.在此基础上,使用多体项展式理论方法,导出了基态SiO2分子的全空间解析势能函数,该势能函数准确再现了SiO2(C2V)平衡结构. 相似文献
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We demonstrate the complete characterization of a sinusoidally driven electro-absorption modulator (EAM) over a range of RF drive voltages and reverse bias conditions. An accurate performance map for the EAM, to be employed as a pulse generator and demultiplexer in an optical time division multiplexed (OTDM) system, can be realized by employing the Frequency Resolved Optical Gating technique. The generated pulses were characterized for chirp, extinction ratio (ER) and pulse width (<4 ps). The optimization of the EAM’s drive conditions is important to ensure that the generated pulses have the required spectral and temporal characteristics to be used in high-speed systems. The ER and pulse width also influence the demultiplexing performance of an EAM in an OTDM system. This is confirmed by utilizing the EAM as a demultiplexer in an 80 Gb/s OTDM system and measuring the BER as a function of the received optical power for various values of the ER and pulse width. It is of paramount importance to accurately characterize the performance of each individual EAM as the modulators characteristics are device dependant, thus optimum performance can be achieved with slight variations to the device’s drive conditions. By employing FROG, an optimum performance map of each specific device can be deduced. Simulations carried out verified the experimental results achieved. 相似文献
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The absorption spectra in strain-free Ge0.992Sn0.008/Si0.3Ge0.61Sn0.09 Quantum Well structure due to direct gap excitons formed in Ge0.992Sn0.008 wells reported by Chang and Chang are reproduced by an empirical expression. Two Gaussian distributions for heavy hole and light hole excitons and two exponential functions describing continuum transitions and The Sommerfeld factors are used for the fit. The expressions are then used to obtain the change in refractive index, Δn, with field (electrorefraction) using the Kramers–Kronig relation. With the calculated changes in absorption and refraction with bias, other performance parameters of an Electro-Absorption Modulator (EAM), like extinction ratio, chirp parameter, and a figure of merit (FoM) defined as the ratio of extinction coefficient and insertion loss, are evaluated. The FoM takes the largest value for 1 μm length of the EAM with 2 V bias applied to the p–i–n structure. The parameters are also calculated for different wavelengths as well as detuning lengths. For applications as short pulse generation the transmission T as a function of bias V should be linear. We have evaluated the best value of bias voltage that makes the sum of second and third derivatives of T with V equal to zero so that the variation of T with V becomes maximally linear for optimum operation as a short pulse generator. 相似文献
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A novel optical switch featured with high repetition rate, short switching window width, and high contrast ratio is proposed and demonstrated for the first time by placing an electroabsorption modulator (EAM) in a terahertz optical asymmetric demultiplexer (TOAD) configuration. The feasibility and main characteristics of the switch are investigated by numerical simulations and experiments. With this EAM-based TOAD, an error-free return-to-zero signal wavelength conversion with 0.62 dB power penalty at 20 Gbit/s is demonstrated. 相似文献
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《等离子体物理论文集》2015,55(9)
Effect of DC bias on the spatio‐temporal distribution of the electron density for L = 25 mm, Vpp = 150 V at p = 10 Pa with VDC = 0 V. The color scales are given in units of 109 cm–3. (Figure 2b of the paper by N.Kh. Bastykova et al.) 相似文献
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Lei Liang Chuan-Tao Zheng Xiao-Qiang Sun Fei Wang Chun-Sheng Ma Da-Ming Zhang 《Fiber and Integrated Optics》2013,32(5):299-315
Abstract A polymer/silica hybrid Mach–Zehnder interferometer thermo-optic switch is experimentally demonstrated. The switch exhibits low power consumption of 7.8 mW, high extinction ratio of 32.6 dB, and short rise and fall times of 107 and 71 μs, respectively. The output spectrum is 50 nm (1,520–1,570 nm), with the extinction ratio level of over 18 dB. The driving-noise tolerance of this device was experimentally investigated by imposing a generated tunable noise on the pure driving signal. The device reveals a voltage-noise budget as high as 1.1 Vpp relative to a driving voltage of 3.0 Vpp for obtaining higher than a 10-dB extinction ratio. 相似文献
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Yasumasa Takagi 《Surface science》2004,559(1):1-15
The structure of the clean Ge(0 0 1) surface is locally and reversibly changed between c(4×2) and p(2×2) by controlling the bias voltage of a scanning tunneling microscopy (STM) below 80 K. It shows hysteresis for the direction of the sample bias voltage change. The c(4×2) structure is observed with the sample bias voltage Vb?−0.7 V. This structure is maintained at Vb?0.7 V with increasing the bias voltage from −0.7 V. When Vb is higher than 0.8 V, the structure changes to p(2×2). This structure is then maintained at Vb?−0.6 V with decreasing the bias voltage from +0.8 V. The area of the structure change can be confined in the single dimer row just under the STM tip using a bias voltage pulse. In particular, the minimum transformed length is four dimers along the dimer row in the transformation from p(2×2) to c(4×2). The observed local change of the reconstruction with hysteresis is attributed to the energy transfer process from the tunneling electron to the Ge lattice in the local electric field due to the STM bias voltage. A phenomenological model is proposed for the structure changes. It is based on a cascade inversion of the dimer buckling orientation along the dimer row. 相似文献
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A time domain optical demultiplexer using electrooptic microring resonator is proposed. The switching window with pico-second order width is generated by using a sinusoidal electrical control voltage to shift the refractive index of the material. The modulation characteristics and switching window of the microring resonator are studied. The dependences of the width and extinction ratio of the switching window on the control voltage are analyzed. The demultiplexing performance of a 40–10 Gbps system is evaluated by numerical simulation technology. Results show that switching windows with required width and extinction ratio can be generated. 相似文献
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T. Stobiecki H. Jankowski T. Gron J. Wenda 《Journal of magnetism and magnetic materials》1981,23(3):299-304
Some electrical and magnetic properties of Gd-Co films obtained by dc sputtering with bias voltage Vb are discussed. We observed a decrease in the compensation temperature and in the anomalous Hall resistivity with increasing bias voltage while the specific resistivity increases. The anisotropy constant, however, increases up to Vb = -200 V, where it reaches a maximum and then it decreases. Electrical conductivity of the films prepared with Vb greater than -100 V showed tunneling character. We conclude that not only resputtering of Gd atoms but also oxidation of Gd takes place during deposition when bias voltage is applied. 相似文献