对称半导体光放大器马赫—曾德尔干涉仪解复用器的开关特性分析

分析以以半导体光放大器（SOA）为基础的对称马赫－曾德尔干涉仪（MZI）解复用器在控制脉冲和信号脉冲反向传播（CPMZ）与同向传播（TPMZ）两种工作模式下的开关特性。研究表明：控制脉冲宽度、半导体光放大器的长度和非线性增益压缩影响着控制脉冲和信号脉冲反向传播开关窗口的大小，是限制控制脉冲和信号脉冲反向传播高速工作的主要因素。当控制脉冲宽度小于半导体光放大器的渡越时间时，如时延量小于于两位的半导体光放大器渡越时间，控制脉冲和信号脉冲以向传播的峰值开关比开始恶化；当控制脉冲宽度超过半导体光放大器的渡越时间时，即使时延量大于两倍的半导体光放大器滤越时间，峰值开关比也出现恶化。因此当控制脉冲和信号脉冲反向传播高速工作时，控制脉冲应尽可能窄，且时延量必须大于两倍的半导体光放大器渡越时间以确保有较高的峰值开关比，而半导体光放大器长度效应对控制脉冲和信号脉冲同向传播的影响甚微。     

控制脉冲形状对太赫兹光非对称解复用器开关特性的影响

在考虑了太赫兹光非对称解复用器 (TOAD)中半导体光放大器 (SOA)的增益饱和与恢复效应的基础上 ,深入研究了超高斯控制脉冲对半导体光放大器的动态增益响应及太赫兹光非对称解复用器开关特性的影响 ,并与高斯控制脉冲的情形进行了比较。结果表明 :相对于高斯控制脉冲而言 ,超高斯控制脉冲使半导体光放大器的增益转折区减小 ,显著影响太赫兹光非对称解复用器的开关窗口形状 ,当信号光相对于控制光时延一定 ,或环时间非对称性及信号光相对于控制光的全部时延一定时 ,超高斯控制脉冲都将使太赫兹光非对称解复用器的最大开关比降低     

控制脉冲形状对太赫我非对称解复用器开关特性的影响

在考虑了太赫兹光非对称解复用器（TOAD）中半导体光放大器（SOA）的增益饱和与恢复效应的基础上，深入研究了超高斯控制脉冲对半导体光放大器的动态增益响应及太赫兹光非对称解复用器开关特性的影响，并与高斯控制脉冲的情形进行了比较。结果表明：相对于高斯控制脉冲而言，超高斯控制脉冲使半导体光放大器的增益转折区减小，显著影响太赫兹光非对称解复用器的开关窗口形状，当信号光相对于控制光时延一定，或环时间非对称性及信号光相对于控制光的全部时延一定时，超高斯控制脉冲都将使太赫兹光非对称解复用器的最大开关比降低。     

使用半导体光放大器的全光解复用器的性能分析

本文对使用半导体光放大器的Sagnac和Mach Zehnder全光解复用器进行了理论分析,在分析中综合考虑了控制脉冲宽度和半导体光放大器长度的影响。分析结果表明这种解复用器可获得的最小开关窗口由控制脉冲宽度和半导体光放大器长度决定,此外由分析可知,不但这种解复用器的开关速率,而且其被解出的分支信号的速率都不受半导体光放大器张弛时间的限制。     

基于SOA和NOLM的光脉冲放大与压缩的设计模型

设计了一种基于半导体光放大器(SOA)和非线性光学环镜(NOLM)的光脉冲放大与压缩的模型。数值研究结果表明:在NOLM中,当调节合适的控制脉冲的输入和初始时延时,具有较低峰值功率、宽度为几十皮秒的高斯信号脉冲经此模型放大压缩后,可以得到脉冲峰值增益高、脉冲宽度窄以及基本无基座的高质量超短信号光脉冲。     

矩形控制脉冲在半导体光放大器中对高斯信号脉冲的压缩效应分析

提出了在半导体光放大器中应用矩形控制脉冲对高斯信号脉冲进行脉冲压缩的新方案.应用Matlab软件数值模拟的结果表明:在保持信号脉冲的峰值增益不变的情况下,具有较高能量的矩形控制脉冲能使输出信号脉冲的宽度得到大幅度压缩.     

掺Er3+飞秒光纤放大器的特性研究

依据二能级速率方程和光传输方程,理论计算了Er3+光纤放大器中Er3+光纤的最佳长度Lc. 以全光纤飞秒激光器输出的孤子脉冲作为种子源,以理论值Lc作为实际采用的光纤长度,实验测量了Er3+光纤放大器在同向泵浦和反向泵浦下信号光的输出功率,得到同向泵浦的增益为20.0dB, 反向泵浦的增益为20.2 dB.同时测量了脉冲宽度随泵浦功率的变化,实验结果表明,随着泵浦功率的增大,输出光脉冲的宽度的压缩效应经历逐渐增强后逐渐减弱的过程.在同向泵浦方式下,可以得到更短的输出脉宽,其最短脉冲宽度为260 fs.     

控制光和信号光频差对太赫兹光非对称解复用器性能的影响

讨论了半导体光放大器中的带间效应，及载流子热效应、谱烧孔效应、双光子吸收以及超快非线性折射等带内效应对半导体光放大器的动态特性的影响，讨论了两种情况：1)保持控制光波长不变而改变信号光频率，2)保持控制光和信号光频率相同而同时改变它们的频率下半导体光放大器的增益、相位动态特性以及太赫兹光非对称解复用器的开关窗口特性。数值结果表明，为了得到较为平坦而窄的开关窗口，控制光波长应与信号光波长相同，且其与半导体光放大器增益谱中心波长的差值应该大一些。     

基于高非线性光子晶体光纤Sagnac环形镜的全光开关

设计了一种新颖的、低开关功率的全光开关. 将高非线性光子晶体光纤和双向抽运掺饵光纤放大器引入Sagnac环形镜内，破坏了环形镜的对称性，利用交叉相位调制作用使反向传输的两路信号光产生非线性相移，从而实现开关效应. 理论分析表明：开关功率与放大器的增益倍数和光子晶体光纤非线性系数的积成反比，在实验中所得开关功率约40 mW，消光比约为15.9 dB，并且信号光透过率随脉冲控制光峰值功率呈余弦变化，实验结果与理论分析相吻合. 关键词： 全光开关 高非线性光子晶体光纤 环形镜 交叉相位调制     

水中受激布里渊散射微弱Stokes信号光的高增益放大

采用脉冲宽度为7.2 ns的种子光注入式倍频Nd:YAG脉冲激光器,以CS₂为放大介质,实验并理论研究了水中受激布里渊散射微弱Stokes光的信号增益随延迟时间、放大器池长、抽运光能量的变化规律. 结果表明,当抽运光脉冲相对信号光脉冲延迟进入放大器,且延迟时间为脉冲宽度的一半,抽运光能量略低于介质受激布里渊散射阈值,选择合适的放大器池长可获得最佳的信号增益. 适当选择抽运光能量,亦可实现微弱信号光的线性放大. 实验中采用独立双池放大系统,当水中Stokes信号光的能量为1 pJ时,信 关键词： 布里渊放大器 信号增益 延迟时间 抽运光能量     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Research on beamforming method for dual-line array with space mismatch between the two line arrays

The performance of port/starboard discrimination of dual-line array will be seriously degraded when the space between the two line arrays of the dual-line array is mismatched. The directivity function of the delay-sum and delay-subtract beamforming is deduced and the port/starboard discrimination of the delay-sum and delay-subtract beamforming is also studied both under the ideal status and the status under which the space between the two line arrays of the dual-line array is mismatched. Analysis results show the delay-subtract beamforming has better performance of port/starboard discrimination. At last, the sea trial results demonstrate the theoretical results.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.