双间隙输出腔开放腔的高频特性分析

 建立了S波段相对论速调管放大器双间隙输出腔开放腔的3维模型。采用时域有限差分法，通过监测激励电流源的响应计算了该双间隙输出腔的谐振频率、有载Q值、场分布以及特性阻抗，并分析了腔体结构尺寸对谐振频率、有载Q值和特性阻抗的影响。研究表明：腔体半径对开放腔的谐振频率影响很大，耦合孔尺寸对腔体谐振频率的影响较小；随着耦合孔张角增加，有载Q值逐渐减小；随着腔体半径增大、间隙的减小，腔体特性阻抗降低。研究结果可为S波段强流相对论速调管放大器双间隙输出腔的设计提供理论依据。     

Selective area rare-earth doping of planar glass samples for monolithic integration of optically passive and active waveguides

Successful demonstration of selective area doping of planar glass samples for monolithic integration of optically passive and active devices on a single chip is presented. Salt solution of erbium was delivered onto pre-sintered germano-silicate samples via a syringe. The samples were then consolidated to form dense glass layers containing regions doped with rare earth. Erbium tri-chloride solution, 0.1 M, was used during the solution doping phase, with the resulting erbium atomic percentage ranging from more than 0.1-0.4%, increasing linearly with the number of drips applied.     

Radial variation of pump and signal intensities in EDFA; accurate prediction by a novel approximation of the fundamental modal field

The doped fiber amplifier has already emerged as the indispensable potential candidate for repeaterless transmission of information processed through single mode. Therefore the fundamental modal field in the doped single-mode fiber needs to be accurately prescribed both in the pump as well as the signal to facilitate further study of their variation with distance. Based on the novel approximation of the fundamental modal field in graded-index fiber, we formulate analytical expression as regards the variation of modal intensity with radial distance from the axis of the fiber both for the pump and the signal fields and estimate such variation for step-index fiber of some typical V values as example. We find that our estimation matches excellently with the available exact results in case of both the pump and the signal and is shown to be much superior to one-parameter Gaussian approximation. In addition, our methodology involves less computation compared to the exact analysis involving cumbersome computation.     

High Speed Demultiplexer Based on a Three-Wavelength SLA

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A Novel Algorithm for Backward-Pumped Raman Amplifier

In this article, a novel semi-analytical algorithm for calculating backward-pumped Raman amplifier is proposed. The algorithm does not need iteration and can greatly save computational time. Simulation results for Raman amplifiers with 25 km, 50 km, and 100 km fibers show that the accuracy of the method is quite satisfying in comparison with the shooting algorithm and the deviation is within 0.02 dB.     

Modeling of cascaded high isolation bidirectional amplification in long-distance fiber-optic time and frequency synchronization system

We propose a physical model of estimating noise and asymmetry brought by high isolation Bi-directional erbiumdoped fiber amplifiers(Bi-EDFAs), no spontaneous lasing even with high gain, in longdistance fiber-optic time and frequency(T/F) synchronization system. It is found that the Rayleigh scattering noise can be suppressed due to the high isolation design, but the amplified spontaneous emission(ASE) noise generated by the high isolation Bi-EDFA and the bidirectional asymmetry of the transmission link caused by the high isolation Bi-EDFA will deteriorate the stability of the system.The calculated results show that under the influence of ASE noise, the frequency instability of a 1200 km system composed of 15 high isolation Bi-EDFAs is 1.773 × 10-13/1 s. And the instability caused by asymmetry is 2.6064 × 10-16/30000–35000 s if the total asymmetric length of the bidirectional link length is 30 m. The intensity noises originating from the laser and detector, the transfer delay fluctuations caused by the variation in ambient temperature and the jitter in laser output wavelength are also studied. The experiment composed of three high isolation Bi-EDFAs is done to confirm the theoretical analysis. In summary, the paper shows that the short-term instability of the T/F synchronization system composed of high isolation Bi-EDFAs is limited by the accumulation of ASE noise of amplifiers and the laser frequency drift, while the long-term instability is limited by the periodic variation in ambient temperature and the asymmetry of the amplifiers.The research results are useful for pointing out the direction to improve the stability of the fiber-optic T/F synchronization system.     

微型气相色谱仪热导检测器放大电路设计

Agilent公司生产的Agilent 3000+系列色谱仪是微型气相色谱仪(micro GC)的典型代表,其热导检测器的信号放大电路和模数转换器(analog-to-digital convertor, ADC)存在功耗大、工作温度过高等不足.文中分析了micro GC电路的功能需求,从选用低噪声的24 bit Δ-Σ ADC ADS1255入手,设计了高共模电压容限、低噪声的全差分放大电路及其他外围电路,并且对全差分放大电路建立了噪声模型,计算了其噪声理论值,优化了系统设计参数.另外,还设计了一个测试平台,对所设计的全差分放大电路和ADC的性能进行了全面的测试评估,结果表明新设计的热导检测器放大电路与ADC的总噪声(以美国材料与试验协会(ASTM)标准值计)仅为1.25 μV,总功耗降低了3.7 W,满足micro GC的功能需求,而且可靠性高、体积小、结构简单,可用于新一代micro GC的研发和生产.     

连续变量量子纠缠增强实验的改进

通过在泵浦光和注入光路中加入高精细度模清洁器及提高实验系统锁定的精度,我们对连续变量量子增强的实验系统加以了改进,初始的EPR纠缠光场的正交振幅及正交位相分量的关联度分别从(2.4±0.2)dB,(2.4±0.2)dB提高至(4.0±0.2)dB,(3.9±0.2)dB,而输出纠缠态光场的关联度分别由原来的(3.0±0.2)dB,(3.0±0.2)dB提高至(5.6±0.2dB),(5.5±0.2)dB。与此前的实验系统相比,纠缠增强的效率及结果均有一定提高。     

EAM-SOA millimeter-wave frequency up-converter for radio-over-fiber applications

We present an optical scheme for photonic frequency up-conversion at the millimeter-wave bands based on Semiconductor Optical Amplifier. The proposed scheme modulates the bias current with the Intermediate Frequency in order to achieve frequency mixing of an incoming optical signal modulated with the Local Oscillator. Theory indicates that the proposed scheme supports data bandwidths in the tens of GHz for LO values above 10 GHz. This scheme allows for photonic integration of the considered optical devices. A laboratory demonstration of the scheme for up-conversion to the 40 GHz band, using narrow-band IF signals, showed relatively low thresholds for the optical input power and bias current level to achieve error free operation: − 14.5 dBm 100 mA for a 64-QAM signal. Spurious-Free Dynamic Range showed an acceptable performance, with a linearity about 52.5 dB·Hz^2/3 for an optical input power of − 6 dBm.     

All-optical method of developing a phase encoded latch by using EDFA

Optics has already proved its meaningful application in information processing and computation, where the parallelism of light is exploited to achieve the desired result. In this communication a novel concept of all-optical memory unit based on phase encoding process is proposed. The unit is simple in architecture comprising phase sifters, mirrors (M′) and two blocks of Erbium doped fiber amplifier. The optical feedback is supported by use of beam splitters and mirrors. It is independent of intensity and therefore requires a small switching power and can work at a bit rate far above 100 Gb/s.