LiNbO3：Fe,M（M=Mg^2＋,Zn^2＋,In^3＋,Sc^3＋）晶体中的信号光 …

分析了掺杂铌酸锂晶体的扇形噪声光的形成机制,讨论了信号光与扇形噪声光之间的光放大竞争问题,结果显示,由于信号光与扇形噪声之间光放大竞争,对于信号光的放大而言,存在一个最佳的光生伏特场,因而存在一个最佳入射泵浦光光强,使得信号光具有最大的放大倍数,同时噪声很弱。     

LiNbO3∶Fe,M(M=Mg2+,Zn2+,In3+,Sc3+)晶体中的信号光与噪声光的竞争

分析了掺杂铌酸锂晶体的扇形噪声光的形成机制,讨论了信号光与扇形噪声光之间的光放大竞争问题.结果显示: 由于信号光与扇形噪声之间光放大竞争,对于信号光的放大而言,存在一个最佳的光生伏特场,因而存在一个最佳入射泵浦光光强,使得信号光具有最大的放大倍数,同时噪声很弱.     

LiNbO_3:Fe,M(M=Mg~(2 ),Zn~(2 ),In~(3 ),Sc~(3 ))晶体中的信号光与噪声光的竞争

分析了掺杂铌酸锂晶体的扇形噪声光的形成机制,讨论了信号光与扇形噪声光之间的光放大竞争问题．结果显示：由于信号光与扇形噪声之间光放大竞争,对于信号光的放大而言,存在一个最佳的光生伏特场,因而存在一个最佳入射泵浦光光强,使得信号光具有最大的放大倍数,同时噪声很弱．     

半导体激光器光输出噪声测量及与电噪声的相关性

采用互谱估计方法测量了半导体激光器的微弱电噪声谱及光噪声谱。结果表明两者在超辐射区有较强的相关性。对光噪声的形成机理分析证明由载流子起伏形成的光噪声与电噪声完全相关，而由外量子效率起伏引起的光噪声与电噪声是不相关的。     

微波光子链路中的附加相位噪声分析

针对模拟微波光子链路中附加相位噪声对微波信号相位噪声的恶化问题,详细研究了光链路中白噪声及有色噪声的产生机理,建立了光链路的附加相位噪声理论模型,阐述了附加相位噪声的变化规律,并通过实验证实了模型的正确性。同时针对本振信号的多路光分配典型应用,提出了EDFA 辅助的附加相位噪声优化措施。实验结果表明所提出的相位噪声模型能够有效地应用于微波光子链路,能对附加相位噪声的分析和优化提供理论依据,具有较大的工程指导意义。     

光外差检测中的量子噪声

本文分析了光外差检测中的量子噪声,探讨本振光功率对量子噪声谱的影响     

采用级连反向泵浦喇曼光纤放大器的长距离光纤传输系统中双重瑞利散射噪声的抑制

给出了反向泵浦喇曼光纤放大器中信号和双重瑞利散射噪声的计算方法,分析了双重瑞利散射噪声的特性,计算了采用光隔离器进行双重瑞利散射噪声抑制时,光隔离器的最佳位置。研究了使用多级反向泵浦喇曼光纤放大器的1080km光纤通信系统的传输特性,比较了信号和双重瑞利散射噪声在加入光隔离器前后沿传输光纤的功率变化。加入光隔离器以后,信号所受的影响不大,但双重瑞利散射噪声能得到有效抑制,可减少约三个数量级。1     

全光波长转换器噪声变换的小信号分析方法

本文利用小信号模型对基于半导体光放大器（SOA）交叉增益调制（XGM）波长转换器的噪声变换进行了理论分析和数据计算,结果表明,泵浦光功率和探测光功率的大小以及光放大器的增益对噪声变换有直接的影响,在适度的输入功率范围内,噪声得到了有效的抑制。     

光折变相干散射噪声

全面介绍了光折变相干散射噪声的研究状况，描述并分析了形成散射噪声的必要条件及理论机制，说明了散射噪声的观测技术及评价标准；总结了抑制噪声的各种方案及噪声的相关应用，最后展望了光折变散射噪声的研究前景。     

IL型半导体激光放大器的噪声

IL型激光放大器(LA)可以用做光功率放大器,也可以用做中继放大器代替复杂的光-电中继器.IL型LA的噪声性能对相干光通信系统的性能至关重要,它直接影响到系统的误码率.我们对IL型LA的强度噪声谱和频率飘移谱,进行了数值计算,并讨论了注入光的噪声谱、注入光功率和锁定相位等对噪声谱的影响.     

Optical orthogonal code-division multiple-access system .I. APDnoise and thermal noise

In an optical multiple-access system, overall system throughput efficiency add significant implementation cost-reduction would be achieved if many users could access a common optical channel at any time without control among users. Recently one such scheme, an optical orthogonal code division multiple-access system (OOCDMA), was introduced by Salehi et al. (1982) for the case of no noise. In this paper, some extensions of that work are presented, including the effects of avalanche photodiode (APD) noise and thermal noise as well as interference for the OOCDMA direct-detection receiver. Since it has been shown that an optical hard-limiter before the receiver correlator can reduce the interference effect for the OOCDMA system in the absence of noise, the hard-limiter role in the presence of thermal and APD noise is also examined     

相干噪声对OCDMA编解码器性能影响的分析

给出了DS-OCDMA系统的各组成部分的数学模型,并对OCDMA系统中的相干噪声产生的基理进行了介绍,在充分考虑了光编解码器中光器件温度特性的基础上,分析了相干噪声的原因,并仿真了其对系统的影响。从对光、电编解码器的仿真结果可看出,当使用电编解码器实现OCDMA时,相干噪声的影响可大大降低,甚至完全避免。     

An example of a hybrid system: coherent optical system with Costasloop in receiver-system for transmission in baseband

The possibility of hybrid system construction is considered in this paper. The coherent optical system is the constituent part of this system. The first part of the system is constructed in passband (optical cable is transmission medium), and the second part of the system is constructed in baseband. The heterodyne optical receiver is used as optical receiver. Estimation is not done just after demodulation, but it is done at the end of the section in baseband. Taking into account shot noise of photodetectors, laser phase noise (transmitter laser and local laser) and noise which is generated during transmission by means of the section in baseband, we determine the performances of the proposed system     

Multichannel system design using optical preamplifiers andaccounting for the effects of phase noise, amplifier noise, and receivernoise

A rigorous and accurate model for multichannel direct detection systems where optical preamplification is used is presented. The model accounts for the influence of an optical bandlimiting filter as well as of a polarization filter. Effects of laser phase noise, of spontaneous emission noise from the amplifier, and of shot noise and thermal noise in the receiver front end are accounted for. The predicted phase noise penalty for a single channel configuration is found. For multichannel system design, it is found that a system with many optical channels and no phase noise should have a channel separation of 9.4 bit rates to have less than 1-dB worst-case crosstalk penalty. For a linewidth of 27% of the bit rate in each channel the required spacing increases to 25 bit rates or more     

Effect of thermal noise and APD noise on the performance ofOPPM-CDMA receivers

The effect of thermal noise and avalanche-photodiode (APD) noise on the performance of optical overlapping pulse-position modulation/code-division multiple-access (OPPM-CDMA) systems with and without double optical hardlimiters is examined. Comparisons with the corresponding optical on-off keying/CDMA (OOK-CDMA) systems are presented as well. The maximum data rate that can be achieved under laser pulsewidth and bit error rate constraints is determined. It is shown that about 10 dB increase in the average power, with respect to the Poisson shot-noise-limited system, is required to compensate for the performance degradation due to thermal noise and APD noise. Moreover, it is indicated that for a bit error rate not exceeding 10^-9, a laser pulsewidth of 0.03 ns, and an average received optical power of -55 dBm, a data rate of more than 3 Gb/s can be achieved per channel when using OPPM-CDMA systems with double optical hardlimiters     

Polarization modulated direct detection optical transmissionsystems

A novel polarization modulated direct detection (PM-DD) system suitable both for binary and multilevel transmission is presented. At the transmitter the optical field is polarization modulated by a standard modulator. The receiver is based on the estimation of the Stokes parameters of the received optical field by means of a direct-detection optical front end and baseband electrical processing. The Poincare sphere rotation induced by the fiber is compensated by means of a purely electronic algorithm and the decision is performed in the Stokes space. The system performance is evaluated by an analytical model when the only relevant noise source is the receiver thermal noise and when erbium-doped optical amplifiers introduce amplified spontaneous emission (ASE) noise. The system is completely compatible with a direct-detection-based optical network, and it is possible to implement efficient multilevel modulation formats     

Source-induced noise in optical systems driven by low-coherencesources

High-power quasimonochromatic light sources may deliver enough power into optical and fiber-optic systems to make the source noise dominant at the system output. With an RMS value proportional to light intensity, this noise limits the system sensitivity and dynamic range to levels which cannot be improved by injecting more light into the system. Source-related noise may originate not only from the source intensity fluctuations, but also from a phase-to-intensity conversion process which is characteristic of many single-spatial-mode multiple-path optical systems. The shape of the power spectral density of the source-induced noise, being critically dependent on the physical structure of the system, is analyzed for a self-homodyne Mach-Zehnder structure and for a recirculating delay line. For single-path communication systems, it is shown that source-originated noise exceeds both shot and thermal noise for a received optical power of only a few tens of microwatts     

谐振式光学陀螺输出精度的提高设计

介绍了谐振式光学陀螺的系统构建及工作原理。针对谐振式光学陀螺系统中引入白噪声而影响其转动输出精度问题,该文从理论上对该系统中各信号间的互相关性原理进行了分析,并提出了一种采用数字低通滤波器对信号进行噪声滤除的处理方式。通过对该陀螺系统进行转动测试和零偏稳定性测试。研究发现,其转动输出信号幅度范围用数字量表示由原来的300减小到60。利用Allan方差对零偏稳定性测试数据进行拟合计算,得出其输出精度由265.29(°)/h提高到62.96(°)/h,结果表明,该系统输出精度得到有效提高。     

降低可见光OFDM系统限幅失真的部分线性压扩变换研究

针对可见光正交频分复用（OFDM）系统发光二极管（LED）限幅失真严重的问题,提出一种部分线性压扩变换方法。输出光功率约束较大或较小时,在发射端对直流光正交频分复用（DCO-OFDM）双极性信号中的正信号或负信号进行线性压缩变换,在接收端对压扩信号进行扩展变换可以有效地减小限幅噪声。输入信号功率一定时,在有效信噪比最大原则下对部分线性压扩变换系数和直流偏置进行优化,系统能够获得最佳性能。仿真实验表明,随着约束光功率增大,系统性能越差,且压缩系数的最优值也越小。随着QAM调制阶数的增加,部分线性压扩变换获得的性能增益越小。      

Zernike矩提高哈特曼波前传感器的鲁棒性

哈特曼波前传感器是自适应光学(AO)系统中常用的波前传感器件,噪声、器件装配误差常常影响其探测波前的能力和精度,进而影响整个系统对波前的实时校正。通过实验证明,引入数字图像处理中的矩技术,无需在硬件上对自适应光学系统进行修改,利用Zernike矩噪声不敏感、旋转不变等特性,对波前传感器CCD数据进行预处理,能够降低系统对噪声的敏感性,减小对器件装配精度的要求。