Optical receiver for VHF multichannel video transmission

Optical receivers for multichannel TV transmission in the VHF band are analyzed and tested from the viewpoints of linearity, sensitivity, and frequency response. Photodiodes and avalanche photodiodes are compared for use as a front-end detector. Optimization of the preamplifiers is studied in terms of both configurations and biasing conditions. Improvement of frequency characteristics, using a Percival coil, is also investigated. It is concluded that a receiver using a photodiode can attain as high a sensitivity as and a greater linearity (around 5 dB) than one using an avalanche photodiode     

IM-DD long-distance multichannel WDM transmission experiments usingEr-doped fiber amplifiers

We have demonstrated multichannel wavelength-division multiplexed optical signal transmission experiments employing Er-doped fiber amplifiers. Four-channel transmission of 459 km and 1500 km experiments and two-channel transmission of 4550 km experiment are described, and the transmission penalty is analyzed. We also discuss the effect of four-wave mixing. The difference of the transmission fiber clearly shows the difference of the optical spectrum due to four-wave mixing after long-distance transmission. The results show the possibility of long-distance multidestination optical communication systems with wavelength-division multiplexed signals combined with Er-doped fiber amplifiers     

Efficient numerical simulation of multichannel WDM transmission systems limited by XPM

For numerical simulation of wavelength-division-multiplexed transmission lines including group-velocity dispersion, self-phase modulation, and cross-phase modulation, the computation time is reduced by almost one order of magnitude. This is done by taking into account the channel walkoff within one split step.     

基于多路摄像的视频运动目标智能分析系统

为实现对视频运动目标落点的准确定位与参数分析,并满足其实时性要求,研发了基于多路视频图像的运动目标智能分析系统。该系统综合利用图像预处理和判读技术,在改进ViBe和Mean-Shift等相关算法的基础上,对视频图像进行连续的实时滤波、目标检测和定位以实现对目标参数的智能分析。同时,提出了基于多路视频信息定位目标落点算法和多摄像机协同调度技术。实验结果表明,该系统具有精度高、实时性强等特点,具有较高的实用价值。     

基于波分复用的红外图像光纤传输系统

针对目前红外搜索跟踪系统中,光纤千兆以太网带宽无法满足多传感器实时图像传输需求,设计了基于波分复用的红外图像光纤传输系统,此系统带宽达到4 Gbps,体积算法不变的情况下,可扩展到8 Gbps,满足红外搜索跟踪系统使用要求。     

基于ARM的无线视频传输系统的设计

设计一套低帧速无线视频传输系统,将个人计算机屏幕上的图像通过无线的方式传输到投影仪上。系统中视频发送端采用普通个人计算机,视频接收端是基于ARM11的嵌入式系统。所传输图像使用JPEG标准进行压缩,传输数据链路为Wi-Fi。该系统主要用于教学、会议等场合。本系统可以减少演示场合的线缆,并省去频繁插拔的麻烦。     

WDM系统传输容量的仿真研究

基于Optisystem详细讨论如何构建一个完整的WDM仿真系统,分别给出4波长和8波长WDM系统在传输距离为340km和500km的合波器与分波器输出信号及其仿真眼图,并进行比较分析.结果表明此仿真系统能够很好的模拟WDM长距离传输系统,为进一步对WDM传输系统进行平滑升级扩容提供参考.     

全光纤波分复用传输系统实验研究

本文报道了一种新颖的波分复用系统－全光纤集成型系统：光发射机由全光纤激光器构成，光传输过程中各节点的上／下载由光纤光栅ADM承担，传输中继则由掺饵光纤放大器完成，在这一全光纤系统上，首次成功地实现了1．2Gbit/s的非归零码、1．2Gbit/s的归零码和2．5GHz、5GHz的模拟信号经100km的传输和下载。     

基于多通道数据传输技术的无线视频监控系统

文章基于现代通信技术的发展现状,结合计算机网络技术,介绍了基于多通道多媒体数据传输技术的无线视频监控系统.该监控系统利用多个无线模块建立若干条通信链路,并根据各链路的通信质量动态调整数据传输模式,兼容多种传输协议,保障了多媒体数据传输的流畅度和清晰度,实现了对所有无线覆盖地区的网络远程监控.     

无线传输移动视频监控系统设计探究

近年来,网络视频监控在各个领域得到了广泛的应用,通过网络监控系统应用,能够为大众提供更好的服务,同时还可以维护社会的稳定,促进我国社会经济的持续发展.本文阐述了网络视频监控系统设计构思,在此基础上,针对网络视频监控系统设计中相关要点及应用效果进行了分析,以供读者参考.     

A low-cost multichannel optical transmission system for videosignals

A novel low-cost multichannel optical transmission system for video signals is described. The system uses time-division multiplex pulse-position modulation (TDPPM). The transmitter and receiver are realized in a standard bipolar process while an external low-cost laser and PIN photodiode are used. A maximum of 16 channels can be multiplexed, while achieving a weighted signal-to-noise ratio (SNR) of 54 dB, a differential gain of 1% and a differential phase of 0.5°. For a launched power of 0 dBm (pulse amplitude), the optical budget for a 45 dB weighted SNR exceeds 20 dB. Besides video signals the system is also capable of handling other signals such as digital coded audio signals or computer data. The feasibility of a four-channel system has been confirmed by measurements     

基于双模视频的存储与传输系统的设计

简述了双模视频的存储与传输的应用需求、MPEG-4标准特性的概念,详细说明视频发送和接收的过程,最后在此基础上提出了一种基于双模视频的存储与传输系统的设计方案.该方案首先给出了系统的设计框架,然后阐述系统的具体运行流程,最后详细地阐述了系统各模块的设计.实验结果表明,系统在目标检测与跟踪的应用中具有较好的应用价值.     

基于PSTN的远程视频传输系统设计与分析

基于PSTN的远程视频传输能够为管理部门提供直观、实时的视觉材料,从而达到降低工作强度,提高工作效率,优化管理结构的目的,因此,设计并分析了PSTN的视频传输系统,利用高效的MPEG-4压缩算法及差错控制,在预定的比特率预算和网络带宽限制下可获得较好的视频重建质量.     

基于3G网络的视频直播传输系统方案设计

实现了标清视频通过3G网络进行直播传输,针对3G网络现状上行速率不足的问题,采用多信道绑定和信道均衡预处理技术,提出系统的解决方案,并给出了系统发送端设备的硬件和软件的实现方案,最后给出样机的测试和试用情况,结果显示该方案的有效性.     

基于FPGA的激光回波数据采集与传输系统

传统的激光测距机只是通过测量激光发射主波和目标反射的回波的时间间隔来测量目标距离的。这种方法简单易行,但是没有充分利用信号波形所携带的信息,没有达到探测系统的最佳信噪比。为了提高信号的信噪比、增加激光测距机的作用距离,可以采用全波形高速采样的方案,这些激光全波形数据可用于后续处理的幅度累加、自相关、互相关等处理,能够有效地提高回波信号的信噪比。本文的工作是这种测距方案的一个重要组成部分,包括高速AD采样、FPGA的时序控制、数据采集和传输等部分。针对激光回波数据采集与实时传输的要求和AD采样芯片的多通道、数据量大、速率快的特点设计了基于现场可编辑逻辑门阵列(FPGA)、单时钟先进先出存储器FIFO(First-In- First-Out)和RS232接口总线的激光回波数据采集与实时传输系统。系统主要以FPGA和RS232协议为核心,主要研究采用状态机设计模块来将系统各个模块联结起来。由FPGA向AD芯片写入配置数据的同时,也接收AD芯片的输出数据并送入到FIFO存储器进行缓存和运算处理,处理好的数据由RS232总线发送给上位机进行数据处理。仿真实验结果表明系统逻辑准确,可以满足激光回波波形实时采集与传输的基本要求。     

基于WDM的多速率无源光接入系统传输实验研究

建立了基于WDM的无源光网络下行方向传输实验系统,信道波长间隔0.8nm,一路为恒定速率NRZ调制,另一路为多速率调制.通道最大插损12.5dB,邻道串扰小于-36dB.信号眼图张开度好、眼皮厚度小,多速率和恒定速率下接收灵敏度分别为-32.28dBm和-27.09dBm,功率代价0.52dB.实验结果表明系统在传输速率较低时主要受功率损耗影响,随着速率的提高,色散和非线性效应成为影响传输性能的重要因素.     

基于C/S模型的视频信息传输系统研究

讨论了IP网络与C／S模型，并对多媒体网络的传输协议作了分析，借助RTP／RTCP协议来确保视频信息传输的质量，采用C／S模型，在Windows2000环境下，设计了一个支持IP组播的视频信息传输系统，用它能够实现IP网络上的实时视频信息传输。     

HFC网VOD系统视频传输技术实现

简要介绍了基于ＨＦＣ网视频点播系统,重点讨论了其视频传输实现技术,分析并描述了视频传输协议最后给出了该系统视频传输的具体实现。     

Frequency up-conversion of optical microwaves for multichannel optical microwave system on a WDM network

We propose a multichannel optical microwave system employing a frequency up-converting optoelectronic oscillator (FU-OEO) [FU-OEO: frequency up-converting optoelectronic oscillator] as a low-phase noise local oscillator (LO) and a multichannel frequency up-converter. Employing the FU-OEO, we demonstrated an optical microwave system capable of 16 optical microwave links in the C-band on a WDM network; the generated optical microwaves were distributed to their designated remote stations according to the channel wavelength. When the FU-OEO was used as the system LO, the phase noise of the optical microwaves was under ?80 dBc/Hz at a 10 kHz offset from a 20 GHz carrier frequency. As a frequency up-converter, the FU-OEO simultaneously up-converted all optical data channels at a 1.25 Gbps data rate for optical microwaves in the 20 GHz band of an optical carrier suppression mode having almost 100% modulation depth. The overall system performance was verified by measuring the bit error rates (BER) of the data recovered from optical microwaves received through single-mode fibers. The measured BER indicated that the system can transmit over 50 km with a power penalty of less than 1 dB. This method can be useful for high-frequency applications where the generation and transmission of optical microwaves are greatly restricted by optical or electrical bandwidths.