非线性相位噪声对DQPSK调制系统性能影响研究

为了研究非线性相位噪声对差分正交相移键控（DQPSK）调制系统性能的影响,在理论推导非线性相位噪声数学模型的基础上,通过固定接收端信噪比不变,仿真分析了40Gb/s速率时DQPSK调制系统误码率随输入信噪比的变化情况。结果表明:与二进制差分相移键控（DPSK）调制相比,DQPSK调制对非线性相位噪声的影响更为敏感,当非线性效应较大时,非线性相位噪声将使系统误码率显著增大,严重影响系统通信质量。因此,当采用DQPSK调制时,必须考虑非线性相位噪声对系统性能的影响。     

平衡接收直接检测DPSK接收机噪声统计特性分析

以带光前置放大器且采用MZI相干和直接检测方式的DPSK接收机为分析模型,从考虑线性附加噪声和非线性相位噪声入手,对噪声统计特性进行了数学分析,并推导出了概率密度函数和BER公式。结果表明:数值计算结果与已发表论文的试验结果较为吻合;非线性相位噪声会对系统性能造成严重影响;高斯近似法不能很好的分析此模型。     

PN9000相位噪声测试系统扩频方法研究

在航天测控领域,相位噪声指标已成为系统性能的限制性因素,精确测量载波的相位噪声显得尤为重要;PN9000相位噪声测试系统可直接应用于相位噪声测试,具备测试灵敏度高、系统稳定、测试快速等优点;随着航天测控领域所用频率的不断提高,针对PN9000相位噪声测试系统基本配置的频率范围已无法满足测试需求的问题,为满足PN9000相位噪声测试系统扩频需求,文中提出基于相位检波器法(基本型)和基于中频相位检波器法两种扩频方法,并对两种方法进行原理分析和实验验证;根据实验结果,两种方法均能有效实现扩频功能,但在系统本底相位噪声及经费使用方面各有不同特点;文中提供的方法及实验数据,对PN9000相位噪声测试系统扩频升级及配件选购等具有很好的借鉴作用。     

无间隙采样在近载频相位噪声测量中的应用

本地振荡器是雷达或通信系统的核心器件,其相位噪声指标决定了发射机和接收机的性能;通过对常用相位噪声测试方法的比较,分析了这几种方法各自的特点,特别是针对时间频率中高分辨率及无间隙测量能力结合的计数器,研究了其在近载频相位噪声中的测试及数据分析处理方法,该方法在查找和消除高性能振荡器的噪声源中具有较大的价值。     

远程干涉型光纤传感系统的非线性相位噪声分析

以远程干涉型光纤传感系统为背景, 研究了系统非线性相位噪声构成, 对各构成要素的具体影响进行了详细分析和综合评价, 简要讨论了噪声抑制方案. 研究表明, 系统相位噪声主要包括强度噪声转化而来的相位噪声、非线性效应引起激光 线宽展宽导致的相位噪声以及自相位调制和交叉相位调制引入的相位噪声. 受激布里渊散射和四波混频可引入强度噪声并转化为相位噪声, 对于探测带宽较窄的光纤传感系统, 四波混频引入的该部分噪声往往可以忽略. 受激布里渊散射、四波混频和调制不稳定性都可引起激光线宽展宽从而造成相位噪声的增大. 当系统信道数目较多时, 交叉相位调制对相位噪声的贡献不可忽略. 所得结论对远程干涉型光纤传感系统的实际应用具有重要的指导意义.     

自动补偿高效的差分相位编码QKD系统

提出一种自动补偿高效实用的改进型差分相位编码量子密钥分发方案.在Alice端采用偏振型强度调制器对连续激光进行调制，产生任意个相干脉冲进行差分相位调制编码；在Bob端采用双FM干涉仪代替传统的M-Z干涉仪，自动补偿了环境引起的偏振抖动，提高了系统的干涉稳定度.简化了系统的结构，提高了密钥生成效率，增强了系统的安全性.在实验上实现了稳定的80km量子密钥分配，误码率<4%. 关键词： 量子保密通信 量子密钥分发 差分相位编码 偏振型强度调制器     

稳定的低噪声自由空间量子密钥分配实验研究

基于量子密钥分配的基本原理,采用偏振短脉冲相干光源和双FM差分密钥分配的方案,进行了自由空间量子密钥分配的实验研究. 该方案具有噪声低,稳定性高,误码率低等优点,为空间量子保密通信提供了一个有意义的实施方案,具有一定的实用价值和学术意义. 关键词： 量子保密通信 量子密钥 自由空间 差分相位编码     

匹配干涉结构对远程光纤传感系统噪声的影响

研究了采用内调制相位产生载波（PGC）解调的匹配干涉型光纤传感系统中匹配干涉结构对传输光纤拾音噪声的影响。结果表明：当补偿干涉仪与传感部分相邻时,光学微分效应的作用可大幅度降低由传输光纤光路拾音引入的相位调制噪声;匹配光程差的增加不仅加剧了光频噪声向相位噪声的转换,同时也会影响相位调制噪声的转换幅度。通过设计合适的匹配光程差,并将补偿干涉仪进行有效屏蔽后与传感部分相邻放置,可以有效减小系统的相位噪声。研究成果为光纤传感远程传输系统的综合设计及噪声抑制技术提供了理论及实验基础,具有一定的参考意义。     

基于法拉第旋镜的干涉型光纤传感系统偏振相位噪声特性研究

偏振诱导信号衰落现象的抑制是干涉型光纤传感系统的关键技术之一. 针对法拉第旋镜(FRM)法抑制偏振诱导信号衰落技术的残留偏振相位噪声问题进行了深入的理论和实验研究. 运用琼斯矩阵法建立了基于法拉第旋镜的干涉型光纤传感系统偏振相位噪声的理论模型; 分析了影响系统偏振相位噪声的主要原因: 法拉第旋镜的旋光角度偏差、入射光偏振态调制度、干涉仪两臂光纤双折射; 提出了相应的抑制偏振相位噪声的方法. 详细仿真分析了入射光偏振态调制度对干涉型光纤传感系统偏振相位噪声的影响, 仿真分析得出若法拉第旋镜旋光角度偏差为最大工艺制造误差1°, 当入射光偏振态调制度为1.84 rad时, 系统可能出现的最大偏振相位噪声为0.0815 rad. 最后, 搭建了基于M-Z型偏振态调制器的偏振相位噪声测试系统, 测试了在传输光纤受到外界偏振扰动的情况下, 干涉传感系统存在的偏振相位噪声, 实验测试结果与理论分析结果基本一致, 有力地证明了该偏振相位噪声理论分析模型的正确性.     

高稳定的差分相位编码量子密钥分发系统

在差分法基础上提出了一种改进的差分相位编码量子密钥分发(QKD)方案.Alice采用脉冲激光光源,通过两个串联光纤延迟环产生四个均匀的相干脉冲，并对脉冲进行差分调制，补偿了传输过程中环境对偏振的扰动.Bob采用双FM干涉仪,在窄脉冲门控模式下进行单光子探测.单程传输避免了木马攻击，增强了方案的安全性.实验结果表明，系统可以长期稳定运转(大于24h)，误码率为3％.改进的系统具有高效、稳定、低成本的优点，实施方便，有很好的实用价值. 关键词： 量子保密通信 量子密钥分发 差分相位编码     

Optimization design of RIS-assisted high-capacity visible light communications based on HDMA

In this paper, a new non-orthogonal multiple access (NOMA) scheme is proposed for the reconfigurable intelligent surface (RIS) assisted high-capacity visible light communication (VLC) system, which is named hybrid domain multiple access (HDMA). HDMA enjoys the benefit of hybrid-domain signals, including the power domain, code domain, and frequency domain, where the message passing algorithm (MPA) and successive interference cancellation (SIC) detectors are jointly used at the HDMA receiver. Furthermore, to achieve a higher communication capacity for the VLC system, we proposed an optimization model by jointly optimizing the power allocation ratio and RIS reflection units. The simulation results verified the proposed scheme. By comparing the system capacity of different RIS allocation schemes and multiple access methods, the VLC system based on HDMA proposed in this paper can significantly improve its communication capacity.     

Study of SAR imaging with COMPASS signal

A concept of space-surface bistatic synthetic aperture radar (SS-BSAR) passive imaging system is proposed,which is parasitic on the signal of COMPASS Navigation Satellite System (CNSS).The feasibility is demonstrated by analyzing the signal ambiguity function and the range resolution as well as the system topology.Due to the multiple peaks of signal in the auto-correlation function,a new correlation is used to remove the side-peaks.A double-channel receiver is employed to receive the direct satellite signal...     

Performance analysis of a hybrid fiber Bragg grating-based spectral-amplitude-coding/successive interference cancellation for optical CDMA systems

Successive interference cancellation (SIC) scheme is proposed as a new technique that has the potential to reduce the interference and suppress the multiple-access interference (MAI) in spectral-amplitude-coding (SAC) optical-code-division-multiple access (OCDMA) systems. The proposed receiver-based on fiber Bragg gratings (FBGs) techniques. The performance of the proposed system is theoretically analyzed, taking into account various types of noise and interference, including both multiple-access interference (MAI) and receiver noise. Analytical results show that the proposed system offers significant improvement in terms of bit error rate and system capacity (number of users). We have tested our results with both modified prime codes (MPR) and modified quadratic congruence (MQC) codes. In addition, we have compared our proposed system with the corresponding one without cancellation. It has been shown that the proposed scheme gives a substantial increase in capacity.     

基于全可编程SoC和LabVIEW的磁共振接收系统设计

本文提出了基于全可编程片上系统（System-on-a-Chip,SoC）和实验室虚拟仪器工程平台（Laboratory Virtual Instrument Engineering Workbench,LabVIEW）的磁共振信号接收系统设计.使用集成了ARM（Advanced RISC Machines）和现场可编程门阵列（Field Programmable Gate Array,FPGA）的全可编程SoC作为接收机的主芯片,利用Xilinx提供的数字信号处理（Digital Signal Processing,DSP）开发工具System Generator设计了数字下变频（Digital Down Converter,DDC）算法,并实现了接收机硬件电路.使用可视化编程平台LabVIEW设计了磁共振上位机软件,完成了磁共振信号的显示、存储和与接收机通信的工作,提高了软件开发效率.实验结果表明,本文设计的接收机能正确接收磁共振回波信号,且具有较高的信噪比.     

Enhanced performance for 10 Gb/s long reach RSOA based WDM-PON by using power pre-emphasized OFDM signal

An extended reach 10 Gb/s wavelength division multiplexing passive optical networks (WDM-PONs) system based on reflective semiconductor optical amplifier (RSOA) is proposed by using power pre-emphasized orthogonal frequency division multiplexing (OFDM) signal. Experimental results show that the proposed technique can effectively enhance the system performance against the limited bandwidth and chirp induced fading effect from direct modulation of RSOA. The receiver sensitivity is improved by 5 dB at the limit of BER for forward error correction (FEC) code over the 60 km and 85 km fiber transmission without any dispersion compensation module.     

基于NI PXIe-7966R的磁共振成像接收机设计

提出了一种基于NI PXIe-7966R（National Instruments Corporation,美国）的磁共振成像（MRI）接收机设计方案,进行磁共振信号直接采样、数字下变频（DDC）和数据上传,以及磁共振图像恢复．使用NI LabVIEW FPGA（National Instruments Corporation,美国）开发平台,对NI PXIe-7966R板载现场可编程门阵列（FPGA）内构建的所有功能模块进行了设计仿真和硬件描述语言生成,使其能灵活实现DDC功能．设计的接收机的采样速度为50 Mbps、模数转换位数为16位、带宽设置范围为100 Hz~1 MHz,并具有较好的滤波效果．实验结果表明,该设计方案是一种高性能的磁共振接收机方案．     

A novel approach for simultaneous millimeter wave generation and high bit rate data transmission for Radio over Fiber (RoF) systems

We propose a novel method for simultaneous transmission of OC-192 (9.95328 Gbps) digital data and 60 GHz RF generation in a Standard Single Mode Fiber (SSMF) link utilizing Stimulated Brillouin Scattering (SBS). The system comprises of a 1550 nm DFB Laser diode, Mach Zehnder modulator (MZM), 50 km SSMF and Optical receiver. The receiver includes laser diode for optical pump, a regenerator for data retrieval and a RF bandpass filter for RF generation. This system requires minimum number of RF and optical components for the generation of 60 GHz RF. The remotely generated 60 GHz RF signal may be used for wireless transmission of data. The entire link is simulated in Optisystem software to analyze the system performance.     

Performance analysis of wavelength/spatial coding system with fixed in-phase code matrices in OCDMA network

This paper proposes a wavelength/spatial (W/S) coding system with fixed in-phase code (FIPC) matrix in the optical code-division multiple-access (OCDMA) network. A scheme is presented to form the FIPC matrix which is applied to construct the W/S OCDMA network. The encoder/decoder in the W/S OCDMA network is fully able to eliminate the multiple-access-interference (MAI) at the balanced photo-detectors (PD), according to fixed in-phase cross correlation. The phase-induced intensity noise (PIIN) related to the power square is markedly suppressed in the receiver by spreading the received power into each PD while the net signal power is kept the same. Simulation results show that the W/S OCDMA network based on the FIPC matrices cannot only completely remove the MAI but effectively suppress the PIIN to upgrade the network performance.     

Pre-amp EDFA ASE noise minimization for optical receiver transmission performance optimization

Amplified spontaneous emission (ASE) noise mitigation from the pre-amp erbium-doped fiber amplifier (EDFA) to the photon detector (PD) in optical receivers can be reduced by optimizing the EDFA at the optical receiver level to achieve optimal optical receiver transmission performance.     

Simulation research of medium-short distance free-space optical communication with optical amplification based on polarization shift keying modulation

Circular polarization shift keying (CPolSK) modulation technique has many advantages such as excellent BER performance and freedom from the alignment of polarization coordinates of the transmitter and the receiver, etc., and it turns out to be a good choice to FSO system. In this paper, a FSO system using CPolSK modulation is studied by simulation; it is found that the communication performance of the system is excellent in most weather condition. Additionally, three ways of optical signal amplification are proposed, and contrastive analysis on performance of corresponding optical amplification systems is carried out by examining SNR、BER and transmission distance with different specific attenuation. The results show that the system with optical amplifier at the transmitter have the optimum performance, and then the system with optical amplifier at the both ends with the same total gain, it is worst for the system with optical amplifier at the receiver. In addition, the safety factor for high emission power induced by optical amplification is also considered in this paper for practical application. The study above may be utilized in the system design for enhancing performance.