视频光端机的作用

视频光端机的作用 光端机的种类: 光端机从接口分类应为视频光端机、音频光端机、数据光端机、电话光端机、以太网光端机。 光端机分3类:PDH，SPDH，SDH。 PDH(Plesiochr onous Digital Hierarchy，准同步数字系列)光端机是小容量光端机，一般是成对应用，也叫点到点应用，容量一般为4E1，8E1，16E1。 SDH(Synchronous Digital Hierarchy，同步数字系列)光端机容量较 大，一般是16E1到4032E1。 SPDH(Synchronous Plesiochronous Digital Hierarchy)光端机，介于PDH 和 SDH 之间。SPDH 是带有 SDH(同步数字系列)特点的 PDH 传输体制(基于 PDH 的码速调整原理，同时又尽可能采用 SDH 中一部分组网技术)。 监控术语的话,那就是 视频光端机,传输视频为主及其他数据,音频,开关量,以太网电话等信号的光电转换传输设备,他的本质是:光电转换传输设备;放在光缆的两端,一收一发,顾名思义光端机;所以广义上讲,基于光纤网络用于传输信号的光电转换设备都可以称为光端机。以此分类用于电信上传输信号(也有压缩的视频)的压缩光端机与用于监控和广播电视行业的非压缩的视频光端机. 平常所说的光端机 概述: 平常所说的光端机是传输视频的非压缩光端机。视频光端机在中国的发展是伴随着监控发展开始的，视频光端机 就是把1到多路的模拟视频信号通过各种编码转换成光信号通过光纤介质来传输的设备，又分为模拟光端机和数字光端机。 视频光端机应用图解 1、模拟光端机 模拟光端机采用了 PFM 调制技术实时传输图象信号。发射端将 模拟视频信号先进行 PFM 调制后，再进行电-光转换，光信号传到接 收端后，进行光-电转换，然后进行 PFM 解调，恢复出视频信号。由 于采用了 PFM 调制技术，其传输距离能达到50Km 或者更远。通过 使用波分复用技术，还可以在一根光纤上实现图象和数据信号的双向 传输，满足监控工程的实际需求。这种模拟光端机也存在一些缺点: a)生产调试较困难; b)单根光纤实现多路图象传输较困难，性能会下降，目前这种模 拟光端机一般只能做到单根光纤上传输4路图象; c)抗干扰能力差，受环境因素影响较大，有温漂; d)由于采用的是模拟调制解调技术，其稳定性不够高，随着使用 时间的增加或环境特 性的变化，光端机的性能也会发生变化，给工程使用带来一些不 便。 2、数字光端机 由于数字技术与传统的模拟技术相比在很多方面都具有明显的 优势，所以正如数字技术在许多领域取代了模拟技术一样，光端机的 数字化也是一种必然趋势。目前，数字视频光端机主要有两种技术方 式:一种是 MPEG II 图象压缩数字光端机，另一种是全数字非压缩 视频光端机。综合布线中长飞光纤光缆的终端盒与光纤耦合器在的光 纤熔接，16路视频光端机比8路视频光端机和4路视频光端机好用。 图象压缩数字光端机一般采用 MPEG II 图象压缩技术，它能将 活动图象压缩成 N×2Mbps 的数据流通过标准电信通信接口传输或者 直接通过光纤传输。由于采用了图象压缩技术，它能大大降低信号传 输带宽。 全数字非压缩视频光端机采用全数字无压缩技术，因此能支持任 何高分辨率运动、静止图像无失真传输;克服了常规的模拟调频、调 相、调幅光端机多路信号同时传输时交调干扰严重、容易受环境干扰 影响、传输质量低劣、长期工作稳定性不高等缺点。并且支持音频双 向、数据双向、开关量双向、以太网、电话等信号的并行传输，现场 接线方便，即插即用。 数字光端机具有明显的优势 与传统的模拟光端机相比，数字光端机具有明显的优势: 1)传输距离较长:可达80Km，甚至更远(120Km); 2)支持视频无损再生中继，因此可以采用多级传输模式; 3)受环境干扰较小，传输质量高; 4)支持的信号容量可达16路，甚至更多(32路、64路)。 二、光端机从模拟走向数字 从上个世纪80年代末模拟光端机开始进入中国应用，到2001年开 始数字光端机的出现;演绎了经济发展带动科学技术进步，科学技术 推动经济发展的过程。 最早出现的模拟光端机主要是采用模拟调频、调幅、调相的方式 将基带的视频、音频、数据等传输信号调制到某一载项，通过另一端 的接收光端机进行解调，恢复成相应的基带视频、音频、数据信号。 把信号调制到光上，通过光纤进行视频传输，通常使用以下几种 调制方式: 调幅或强调制系统(AM):全模拟系统，光学发射单元内发光二 极管(LED)的亮度或强度随输入视频幅度线性变化。调幅的光信号通 过光纤发送给光接收单元，由其将信号转换为模拟基带视频。 调频或脉冲频率调制(FM):也是一个模拟系统，射频载波通过输 入的视频信号线性调节频率，经过调制的载波又用于光发射单元 的 LED 或激光发射器，经过频率调制的信号通过光纤发送给光接收单 元，由其将信号转换为模拟基带视频。 AM 视频传输被广泛用于工业安全市场上从低端到中端 CCTV 监 视及安全应用场合。适用于5.5公里(3.5英里)或更短距离的传输，这样 一个系统能够提供的定性视频性能是相当不错的，并且总是能够达到 RS-250C 长距离传输的品质要求。但是，AM 视频传输设备仅适合 850nm。多模工作波长这就限制了最大可用传输距离。更显著的是， 对于每1dB 的光学路径损耗而言，基于调幅系统的信噪比的线性相关 衰减为2dB，因此，可接受的视频传输质量仅能在相对较短的光缆距 ItAAAASA Close to the desired solution was prepared, and then use the reference material (or another material standard) to determine its exact concentration. This determines its exact concentration is called calibration. For example, for the preparation of 0.1mol • L-1HCl standard solution, first with a certain amount of concentrated HCl diluted with water, mixed concentration is about 0.1mol • L-1 in dilute solution, and then use the anhydrous Na2CO3 benchmark solution titration accurately weigh the material until both quantitative response fully, and then consumed in the titration of aqueous solution of HCl volume and quality of anhydrous Na2CO3, calculate the exact concentration of the HCl solution. Most accurate concentrations of the standard solution are determined by calibration of the method. Constant component in the determination of standard solution concentration range of 0.01 mol • L-1-1 mol • L-1, typically according to the components to be tested to select the height of the size of standard solution concentration. In order to improve the accuracy of calibration, calibration should pay attention to the following points: ? determination of calibration should be parallel 3-4, repeated at least three times, and called for determination of the relative deviation is less than 0.2%. ? in order to reduce measurement error, weighing the baseline amount of substance should not be too few, weighing at least 0.2G above; same titration at the end consumption of standard solutions or too small in size, the best is 20mL. C preparation of calibration solutions and use liquor, such as glassware, such as volumetric flasks and pipettes, where necessary, corrected volume, and considering the effect of temperature. D calibration good of standardOperated by stock solution was prepared solution, in principle only be diluted once, if necessary, dilute the secondary. Dilution of too many accumulated error is too large, affect the accuracy of the results. 2. calibration cannot be directly made accurate concentrations of the standard solution, first solution was prepared, and then select the base material calibration. Do the titration with acid and alkali solution, it is usually prepared with about 0.1mol • The concentration of L-1. Of solid acid and alkali solution prepared from original, generally only accurate to 1~2 significant figures, it can be graduated cylinders measuring liquids or solid reagents weigh in the scales, add the solvent (water), graduated cylinder or measuring cup amounts. But in the whole process of calibration solution, everything is very strict and accurate. Weighing standard substances requires the use of analytical balance, accurate to four digits after the decimal point. Volume calibration solution, if it were to participate in the concentration are calculated using volumetric flasks, pipettes, burets accurate operation, not sloppy. (B) the general solution preparation and preservation methods of 1:1 (or 1+1), 1:2 (1+2) volume is expressed as concentration. For example, 1:1 solution of H2SO4, the original concentrated H2SO4 volume 1 volume, mix with 1 volume of water. And as 1:3 HCl, the original volume 1 volume hydrochloric acid and three volumes of water and mix. Preparation of solution, according to the requirements on the accuracy of solution concentration should be determined on the balance at the level of the weighing; record should be written to several significant figures; the prepared solution choose what kind of vessel. That accurate, it should be very strict tolerances can be less stringent. The "quantity" concept 长沙威普讯通信技术有限公司 www.cswpx.com 离下获得。一些生产商的设备可能在初始安装阶段需要接收机增益调 节，从而使安装过程复杂化。最后一点，AM 产品达不到今天 ITS 及 高端工业安全应用中所需达到的 RS-250C 中短距离视频传输技术要 求。 FM 视频传输是曾广泛应用于 ITS 及高端工业安全市场的传输方 式。能够提供极高质量的视频传输性能，通常能达到 RS-250C 中距 离传输的质量要求并且成本合理。不象 AM 设备，FM 产品适用于 1330nm。多模或单模操作，以及1550nm。单模操作，其典型应用的 传输距离可达66公里(42英里){客户需要可达80KM,。无需为了方便 安装而要求用户进行调节。尽管 FM 方式能够提供高质量传输，但是 其信噪比在更高水平的光衰减，或者更长的传输距离的光缆传输过程 中会衰减，并且信噪比与光衰减之间不再是线性关系，因此其性能并 不是可以完全预测或保持不变的。 另外，基于调频的系统很难达到 RS-250C 短距离传输的技术要 求，而且调频视频发射与接收单元也容易受到外界电磁源以及来自蜂 窝电话和手机等的无线电波的干扰(EMI/RFI)，通常出现在野外或路 边环境中。 受技术限制，光端机主要有单路、双路、四路、八路视 频及带 PTZ 控制数据的光端机，在一芯上传输实现点对点，传输容 量严重不足对于具有足够传输容量的光纤造成了浪费，复杂的、大容 量、高路数的设备则需要多芯传输;加上模拟视频技术的缺陷带来的 易受干扰、易衰减的特点，实现多级中继、级联比较困难，传输业务 的单一化(一般只有视频及数据信号)，模拟视频传输在应用了粗波分 复用也同样受技术条件和波分复用设备价格昂贵的限制，在光纤及光 传输设备昂贵的年代许多行业即使有明确的需求也望而 光传输设备 却步其应用了。多路信号同传引起的交调失真。 在现场监控应用中，用户可能有许多各种信号，如视频图像、音 频、数据、以太网、电话或其它用户自定义的信号，为了提高光纤的 利用效率，降低成本，必须将各种信号在光端机进行复用，以便在一 对或一根光纤上传输。对调频、调幅、调相光端机来讲，将多路视频、 音频或数据信号混合调频、调幅、调相在某一载波上必然会引起各种 镜像、交调干扰。所以目前市场上不乏很多著名国外品牌的调频、调 幅、调相光端机多路视频、音频、数据同传时出现相互干扰的现象， 这些不稳定的现象都是模拟调制技术长期以来一直所固有的缺点。 数字光端机传输的是数字信号，很容易进行大容量复用并且不会 出现相互干扰。对于日益发展的市场需求，模拟光端机已经不能适应 大容量、多业务(视频、数据、音频、开关量、以太网、对讲、电话 等)传输的要求，多路串扰、易衰减、易老化的、售后服务麻烦等问 题使得模拟光端机逐渐随着新技术的出现，市场和应用走向了下坡 路。 数字光端机的出现解决了模拟光端机所出现的问题。2000年开始 通讯技术的发展使得光传输器件技术和数字视频技术的发展，数字光 地址:长沙威普讯通信技术有限公司 网址:www.cswpx.com 客户服务联系电话:0731 88650578 端机开始走向了市场及行业的应用。随着数字光端机和模拟光端机的 的对比发展，慢慢数字光端机开始逐渐代替模拟光端机，到目前为止 已经形成了模拟光端机和数字光端机二八分天下的局面。相信不久的 将来模拟光端机只能成为监控史上的一个名词。如果说早期模拟光端 机是国外光端机厂商带来的最早的传输市场，那么数字光端机可就是 国内和国外竞力，国内厂商优势与国外厂商的一个过程。 最新一代光纤视频传输设备借助于光学传输单元内部的一个模- 数转换器或数字信号编码器(编码/解码器)，对于输入的模拟基带视频 信号(来自 CCTV 摄像机视频、音频、数据、开关量、以太网等)采用 数字解码技术进行处理。然后数字信号又调制到 LED 或激光发射器 上，通过光纤传输到光接收单元，在这里先前的数字信号被一个内部 的数-模转换器重新转化为模拟基带视频信号。这样，系统在电气上 完全透明地将光发射器的视频输入通过光纤发送到了光接收单元的 视频输出，并且能够直接匹配目前使用的 NTSC、PAL 或 SECAM 制 式 CCTV 摄像机。 可以说，将模拟信号进行数字化处理后再进行传输是光端机技术 质的飞跃发展。数字光端机解决了模拟光端机的传输容量少、业务能 力少、信号易衰减、易串扰等缺点，优势突显:传输容量大、业务种 类多，单纤传输容量可达几十路上百路非压缩视频，传输的业务也多 样化的传输视频、音频、数据、以太网、电话信号、开关量等各种信 号。这样节省了光纤，也提高了光纤带宽的利用率，提高了性价比; 信号质量的提升到更高的层次，视频图象的信噪比在10bit 编码量化 下可达到67~70db，远远超出了远距离下模拟信号的50~60db 的参数 指标。在级联技术应用了更是得心应手于模拟光端机。 当我们讨论数字解码视频传输设备时，评价产品与产品之间的性 能时所需考虑的性能参数是系统所使用的数字位数。数字位数从根本 上定义了系统的电气动态范围以及端到端的信噪比，并且是视频传输 性能的主要影响因素。现在任何一个分辨率为6位的系统从技术上讲 都是落后的，不能代表目前的最高技术水准，这样的系统肯定会产生 图像上可见的非自然信号以及视频衰减。有鉴于此，在一个数字解码 视频传输系统中所采用的比特数最少应为8位。8位的分辨率或解码能 力能够使视频传输品质满足或超过 RS-250C 短距离传输或真正的视 频传播质量要求。 采用数字非压缩技术、10位数字式视频编码技术(10bit)和15Mhz 采样频率技术使得视频数字化过程时的数字采样点的表示更为精确 , 得到的图像效果更逼真,更加完美。 三、光端机的传输距离 传输距离是指光端机实际可传输光信号的最大距离。这是个标称 数值，它取决于设备和实际环境等多种因素,双纤的光端机一般可传 输1到120KM,单纤的一般可传输1到80KM。 光端机现在出现电话光端机，其目的是通过光纤来传输电话语音 的光通信设备，设备可通过一对光缆传输1-720路电话，是远距离传 输电话，屏蔽机房，电话超市，小区放号的最佳选择。 ItAAAASA Close to the desired solution was prepared, and then use the reference material (or another material standard) to determine its exact concentration. This determines its exact concentration is called calibration. For example, for the preparation of 0.1mol • L-1HCl standard solution, first with a certain amount of concentrated HCl diluted with water, mixed concentration is about 0.1mol • L-1 in dilute solution, and then use the anhydrous Na2CO3 benchmark solution titration accurately weigh the material until both quantitative response fully, and then consumed in the titration of aqueous solution of HCl volume and quality of anhydrous Na2CO3, calculate the exact concentration of the HCl solution. Most accurate concentrations of the standard solution are determined by calibration of the method. Constant component in the determination of standard solution concentration range of 0.01 mol • L-1-1 mol • L-1, typically according to the components to be tested to select the height of the size of standard solution concentration. In order to improve the accuracy of calibration, calibration should pay attention to the following points: ? determination of calibration should be parallel 3-4, repeated at least three times, and called for determination of the relative deviation is less than 0.2%. ? in order to reduce measurement error, weighing the baseline amount of substance should not be too few, weighing at least 0.2G above; same titration at the end consumption of standard solutions or too small in size, the best is 20mL. C preparation of calibration solutions and use liquor, such as glassware, such as volumetric flasks and pipettes, where necessary, corrected volume, and considering the effect of temperature. D calibration good of standardOperated by stock solution was prepared solution, in principle only be diluted once, if necessary, dilute the secondary. Dilution of too many accumulated error is too large, affect the accuracy of the results. 2. calibration cannot be directly made accurate concentrations of the standard solution, first solution was prepared, and then select the base material calibration. Do the titration with acid and alkali solution, it is usually prepared with about 0.1mol • The concentration of L-1. Of solid acid and alkali solution prepared from original, generally only accurate to 1~2 significant figures, it can be graduated cylinders measuring liquids or solid reagents weigh in the scales, add the solvent (water), graduated cylinder or measuring cup amounts. But in the whole process of calibration solution, everything is very strict and accurate. Weighing standard substances requires the use of analytical balance, accurate to four digits after the decimal point. Volume calibration solution, if it were to participate in the concentration are calculated using volumetric flasks, pipettes, burets accurate operation, not sloppy. (B) the general solution preparation and preservation methods of 1:1 (or 1+1), 1:2 (1+2) volume is expressed as concentration. For example, 1:1 solution of H2SO4, the original concentrated H2SO4 volume 1 volume, mix with 1 volume of water. And as 1:3 HCl, the original volume 1 volume hydrochloric acid and three volumes of water and mix. Preparation of solution, according to the requirements on the accuracy of solution concentration should be determined on the balance at the level of the weighing; record should be written to several significant figures; the prepared solution choose what kind of vessel. That accurate, it should be very strict tolerances can be less stringent. The "quantity" concept 长沙威普讯通信技术有限公司 www.cswpx.com 四、光端机接口类型 光端机的典型物理接口如下: BNC 接口 BNC 接口是指同轴电缆接口，BNC 接口用于75欧同轴电缆连接 用，提供收(RX)、发(TX)两个通道，它用于非平衡信号的连接。 光纤接口 光纤接口是用来连接光纤线缆的物理接口。通常有 SC、ST、FC 等几种类型，它们由日本 NTT 公司开发。FC 是 Ferrule Connector 的 缩写，其外部加强方式是采用金属套，紧固方式为螺丝扣。ST 接口 通常用于10Base-F，SC 接口通常用于100Base-FX。 RJ-45接口 RJ-45接口是以太网最为常用的接口，RJ-45是一个常用名称，指 的是由 IEC(60)603-7标准化，使用由国际性的接插件标准定义的8个 位置(8针)的模块化插孔或者插头。 RS-232接口 RS-232-C 接口(又称 EIA RS-232-C)是目前最常用的一种串行通 讯接口。它是在1970年由美国电子工业协会(EIA)联合贝尔系统、 调 制解调器厂家及计算机终端生产厂家共同制定的用于串行通讯的标 准。它的全名是“数据终端设备(DTE)和数据通讯设备(DCE)之间串行 二进制数据交换接口技术标准”。该标准规定采用一个25个脚的 DB25 连接器，对连接器的每个引脚的信号内容加以规定，还对各种信号的 电平加以规定。(目前多用 DB9) RJ-11接口 RJ-11接口就是我们平时所说的电话线接口。RJ-11是用于西部电 子公司(Western Electric)开发的接插件的通用名称。其外形定义为6针 的连接器件。原名为 WExW，这里的 x 表示“活性”，触点或者打线针。 例如， WE6W 有全部6个触点，编号1到6, WE4W 界面只使用4针， 最外面的两个触点(1和6) 不用，WE2W 只使用中间两针(即电话线接 口用) 五、PDH 光端机介绍 PDH 光端机是以超大规模集成电路构成的120路光电合一传输设 备。可提供4个 E1，适用于小容量交换机组网、用户环路网，移动通信(基站)、专网、DDN 网等。特点是体积小，使用方便。 主要特点 采用超大规模集成芯片，具有功耗低，可靠性高的特点。 提供 E1的远端环回测试功能，维护方便。 120提供4个 E1通道; 具有完备的告警功能，可显示本端和远端告警。 告警信息(包括掉电告警)可通过网管通道上报到对端。 采用收发一体光器件，工作性能稳定可靠。 整机单板设计体积小巧，使用方便。 判断光端机参数的主要指标 目前市场上多路数字视频光端机，涉及的技术指标种类繁多，大 部分工程商和用户也缺乏相应的手段而无法判断技术指标的合理性 地址:长沙威普讯通信技术有限公司 网址:www.cswpx.com 客户服务联系电话:0731 88650578 与真实性，因此在选择产品时容易迷失方向。 下面介绍几个光端机参数的指标: 1.技术指标考虑，有视频带宽足够、APL 范围足够宽、信噪比(SNR) 大等等。 2.可靠性考虑。供电方便，电源范围宽。 供电是保证数字视频光端 机可靠性的首要考虑要素，供电不能保证可靠、合理，谈数字视频光 端机的可靠性就成了水中捞月。温度、湿度适应性强。还有接地考虑、 端口保护等等。 3.实用性考虑。外观大方，结构合理;接口丰富，布局合理;最重要 的是指示灯含义明确，方便工程开通和维护。 如何正确的认识光端机，以及如何选择我们所需要的光端机已经变得 尤为重要.下面我们将简单的从国家对光端机的标准和各技术参数对 光端机的影响方面熟悉下光端机。 光端机参数性能介绍: 模拟光端机系列: ?采用频率调制方法,降低了重影,抖动及通道间串扰,从而达到极佳 的传输质量. ?可适应多种恶劣的环境. ?兼容 NTSC,PAL,SECAM 多种制式. ?支持通过一根光纤传输八路视频. ?独立式和插卡式结构. ?带电热插拔,即插即用. ?自动恢复过载保护. ?实时传输. ?无电磁干扰,无射频干扰,无地电流. ?表面贴装技术. ?BNC 视频连接器. ?ST,FC 光学连接器 ?单模光纤允许最大链损为 18dB(DFB 可达 29dB). ?超级光学动态范围,使用无需调节. 光端机技术参数: 数据: 信号输入/输出: 1Vp-p 阻 抗: 75Ω 带 宽: 10HZ-8MHZ 信号接口: BNC 不平衡 微分增益(DG):<3% 微分相位(DP):100,000 小时 数字视频光端机系列: ?采用当今世界最新的 10 位数字式编码技术,通过单模或多模光纤 传输,可达到真正的广播级视频传输品质. ?即插即用的设计,使安装极其简便,并采用先进的自适应技术,使用 时无需调节. ?完全色彩兼容. ItAAAASA Close to the desired solution was prepared, and then use the reference material (or another material standard) to determine its exact concentration. This determines its exact concentration is called calibration. For example, for the preparation of 0.1mol • L-1HCl standard solution, first with a certain amount of concentrated HCl diluted with water, mixed concentration is about 0.1mol • L-1 in dilute solution, and then use the anhydrous Na2CO3 benchmark solution titration accurately weigh the material until both quantitative response fully, and then consumed in the titration of aqueous solution of HCl volume and quality of anhydrous Na2CO3, calculate the exact concentration of the HCl solution. Most accurate concentrations of the standard solution are determined by calibration of the method. Constant component in the determination of standard solution concentration range of 0.01 mol • L-1-1 mol • L-1, typically according to the components to be tested to select the height of the size of standard solution concentration. In order to improve the accuracy of calibration, calibration should pay attention to the following points: ? determination of calibration should be parallel 3-4, repeated at least three times, and called for determination of the relative deviation is less than 0.2%. ? in order to reduce measurement error, weighing the baseline amount of substance should not be too few, weighing at least 0.2G above; same titration at the end consumption of standard solutions or too small in size, the best is 20mL. C preparation of calibration solutions and use liquor, such as glassware, such as volumetric flasks and pipettes, where necessary, corrected volume, and considering the effect of temperature. D calibration good of standardOperated by stock solution was prepared solution, in principle only be diluted once, if necessary, dilute the secondary. Dilution of too many accumulated error is too large, affect the accuracy of the results. 2. calibration cannot be directly made accurate concentrations of the standard solution, first solution was prepared, and then select the base material calibration. Do the titration with acid and alkali solution, it is usually prepared with about 0.1mol • The concentration of L-1. Of solid acid and alkali solution prepared from original, generally only accurate to 1~2 significant figures, it can be graduated cylinders measuring liquids or solid reagents weigh in the scales, add the solvent (water), graduated cylinder or measuring cup amounts. But in the whole process of calibration solution, everything is very strict and accurate. Weighing standard substances requires the use of analytical balance, accurate to four digits after the decimal point. Volume calibration solution, if it were to participate in the concentration are calculated using volumetric flasks, pipettes, burets accurate operation, not sloppy. (B) the general solution preparation and preservation methods of 1:1 (or 1+1), 1:2 (1+2) volume is expressed as concentration. For example, 1:1 solution of H2SO4, the original concentrated H2SO4 volume 1 volume, mix with 1 volume of water. And as 1:3 HCl, the original volume 1 volume hydrochloric acid and three volumes of water and mix. Preparation of solution, according to the requirements on the accuracy of solution concentration should be determined on the balance at the level of the weighing; record should be written to several significant figures; the prepared solution choose what kind of vessel. That accurate, it should be very strict tolerances can be less stringent. The "quantity" concept 长沙威普讯通信技术有限公司 www.cswpx.com ?LED 状态指示器可监视所有关键的运行参数. ?无模拟调频,调相,调幅光端机的交调干扰. ?支持任何高分辩率视频信号. ?支持视频无损再生中继. ?自动兼容 PAL,NTSC,SECAM 视频制式. ?支持(1-32)路视频(路数可调),音频(路数可调),数据(路数可调), 以太网(路数可调),电话语音并行传输. ?千兆光纤传输技术,大容量,易升级. ?光纤 WDM/CWDM/DWDM 技术. ?单,多模光纤传输,距离 0-100KM. ?专用 ASIC 设计及高速 DSP 技术. ?全表面贴装技术. ?工业级设计,可靠性高. ?独立模块或机架式. 光端机的使用和光端机的作用 在近年来各市县的有线电视系统技术改造中，光端机的使用在 光通信领域明显扩大，光纤传输以其损耗低、抗干扰、容量大等诸多 优点获得广泛应用，但由于这是一种新技术，如果系统设计和设备选 用不合理，将会给系统带来不可弥补的损失。综合布线中长飞光纤光 缆的终端盒与光纤耦合器在的光纤熔接，16 路视频光端机比 8 路视 频光端机和 4 路视频光端机好用。 下面就市县 HFC(光纤、同轴电缆混合传输)系统建设中如何合理选 用光发射机、光接收机的问题进行探讨。 1 光端机选用原则 (1)较高的性价比 各种品牌的光端机其性能指标不尽一样，价格相差也极为悬殊。在选 择时可根据网络设计指标并结合自身经济状况进行综合考察，尽量选 择性能价格比高的品牌。 (2)可靠的质量保证体系 生产组装光端机的厂家各自的经济实力和技术实力相差极大，而产品 的可靠性又必须经过较长时期的实际运行才能检验出来。那些经济、 技术实力较差的厂家难免在市场竞争中被 淘汰，其产品一旦出现问题亦将给系统造成巨大的经济损失和影响。 (3)良好的售后服务保障体系 在选择品牌时，厂家售后服务及时、保障系统安全运行也是选型的原 则之一。 除了以上 3 条原则以外，产品是否经广电部门批准入网，是否经 合格，以及厂家有关资质等也是在产品选型时必须考虑的因素。 国外名牌光端机使用优异线性化的 M-2 光外调制器及优异的 SBS 抑制 技术，加上先进的数字化驱动电路及微处理机控制系统，可自动将系 统性能调整在最优化的状态，与 EDFA 光放大 器配合使用，可以传送 CATV 信号达 120 km 以上而仍能保持良好的信 号品质，具有很好的适应性，通过后台软件控制 SBS 值可调整。同时 地址:长沙威普讯通信技术有限公司 网址:www.cswpx.com 客户服务联系电话:0731 88650578 由于是双光回路输出，可经济有效地适用于光 环路网络，采用双电源备份设计，建立更可靠的网络系统。 3 光端机的使用、保养与维护 (1)光端机的使用中要保证连续、正常供电 光端机的激光器组件和光电转换模块最忌瞬时脉冲电流的冲击，因此 不宜频繁开关机。在光端机集中的中心前端机房与 1 550 nm 光发射 机光放大器设置点应配置 UPS 电源，以保护激光组件，使光电转换模 块免受脉冲大电流的损害。 (2)光端机的使用中要保持有一个通风、散热、防潮、整洁的工作 环境 光发射机的激光器组件是设备的心脏，对工作条件要求较高，为了保 证设备正常工作，生产厂家在设备内设置了制冷、排热系统，但当周 围环境温度超过允许范围时，设备就不能正常工作，因此在炎热的季 节，当中心机房发热设备多，通风散热条件又差时，最好安装空调系 统以保证光端机正常工作。 光纤纤芯工作直径为微米级，细小的尘埃进入尾纤活动接口内就会阻 挡光信号的传播，引起光功率大幅度下降，系统信噪比降低，这类故 障率约为 50%，因此机房的清洁卫生也很重要。 (3)光端机的使用中要运行监测与 光端机设备内设置有微处理器，监测系统内部工作状态采集模块的各 种工作参数，并通过 LED 和 VFD 显示系统直观显示，为了及时提醒值 机人员，光发射机内设置了声光报警系统，维护人员只要根据运行参 数确定故障原因，并及时进行处理，就能保障系统正常运行。 光端机的作用 光端机的作用主要是将多个 E1(一种中继线路的数据传输标准，通 常速率为 2.048Mbps，此标准为中国和欧洲采用)信号变成光信号并 传输的设备(它的作用主要就是实现电-光和 光-电转换)。光端机根据传输 E1 口数量的多少，价格也不同。一般 最小的光端机可以传输 4 个 E1，目前最大的光端机可以传输 4032 个 E1。 光端机的作用还有，在光通信系统中的传输设备，进行光电转换及传 输功用。一般用于电信、电力、监控、工业控制、视频传输等功能， 在各个行业有着广泛的应用。常说的光端机指的是用于监控系统用来 传输视频、数据、以太网、音频等综合信息的光端机。主要分模拟光 端机和数字光端机。基于传输的介质的不同有单模光端机和多模光端 机之分。 光端机是用来将光信号和电信号互相转换的一种设备,对所传信号不 会进行任何压缩.而网络视频服务器是用来对模拟视频信号进行数字 化的一种设备,一般会对数字信号进行压缩。 光端机分光发射机和关接收机，光发射机是接受电信号，转换成在光 纤中传输的光信号，而光接受机。 网络视频服务器是接受模拟的音视频信号，可以是摄像机和监听头直 接的信号，经过数字压缩编码，流行的是 MPEG-4,进行网络传输的专 ItAAAASA Close to the desired solution was prepared, and then use the reference material (or another material standard) to determine its exact concentration. This determines its exact concentration is called calibration. For example, for the preparation of 0.1mol • L-1HCl standard solution, first with a certain amount of concentrated HCl diluted with water, mixed concentration is about 0.1mol • L-1 in dilute solution, and then use the anhydrous Na2CO3 benchmark solution titration accurately weigh the material until both quantitative response fully, and then consumed in the titration of aqueous solution of HCl volume and quality of anhydrous Na2CO3, calculate the exact concentration of the HCl solution. Most accurate concentrations of the standard solution are determined by calibration of the method. Constant component in the determination of standard solution concentration range of 0.01 mol • L-1-1 mol • L-1, typically according to the components to be tested to select the height of the size of standard solution concentration. In order to improve the accuracy of calibration, calibration should pay attention to the following points: ? determination of calibration should be parallel 3-4, repeated at least three times, and called for determination of the relative deviation is less than 0.2%. ? in order to reduce measurement error, weighing the baseline amount of substance should not be too few, weighing at least 0.2G above; same titration at the end consumption of standard solutions or too small in size, the best is 20mL. C preparation of calibration solutions and use liquor, such as glassware, such as volumetric flasks and pipettes, where necessary, corrected volume, and considering the effect of temperature. D calibration good of standardOperated by stock solution was prepared solution, in principle only be diluted once, if necessary, dilute the secondary. Dilution of too many accumulated error is too large, affect the accuracy of the results. 2. calibration cannot be directly made accurate concentrations of the standard solution, first solution was prepared, and then select the base material calibration. Do the titration with acid and alkali solution, it is usually prepared with about 0.1mol • The concentration of L-1. Of solid acid and alkali solution prepared from original, generally only accurate to 1~2 significant figures, it can be graduated cylinders measuring liquids or solid reagents weigh in the scales, add the solvent (water), graduated cylinder or measuring cup amounts. But in the whole process of calibration solution, everything is very strict and accurate. Weighing standard substances requires the use of analytical balance, accurate to four digits after the decimal point. Volume calibration solution, if it were to participate in the concentration are calculated using volumetric flasks, pipettes, burets accurate operation, not sloppy. (B) the general solution preparation and preservation methods of 1:1 (or 1+1), 1:2 (1+2) volume is expressed as concentration. For example, 1:1 solution of H2SO4, the original concentrated H2SO4 volume 1 volume, mix with 1 volume of water. And as 1:3 HCl, the original volume 1 volume hydrochloric acid and three volumes of water and mix. Preparation of solution, according to the requirements on the accuracy of solution concentration should be determined on the balance at the level of the weighing; record should be written to several significant figures; the prepared solution choose what kind of vessel. That accurate, it should be very strict tolerances can be less stringent. The "quantity" concept 长沙威普讯通信技术有限公司 www.cswpx.com 用设备，视频服务器一般都带有以太网 RJ- 45 接口和光纤 FC 接口,还带有 SCSi 接口外接硬盘进行前端存储，他 是常用语远程网络监控系统中的最加设备。 六、光端机系列产品 视频光端机 音频光端机 地址:长沙威普讯通信技术有限公司 网址:www.cswpx.com 客户服务联系电话:0731 88650578 电话光端机 ItAAAASA Close to the desired solution was prepared, and then use the reference material (or another material standard) to determine its exact concentration. This determines its exact concentration is called calibration. For example, for the preparation of 0.1mol • L-1HCl standard solution, first with a certain amount of concentrated HCl diluted with water, mixed concentration is about 0.1mol • L-1 in dilute solution, and then use the anhydrous Na2CO3 benchmark solution titration accurately weigh the material until both quantitative response fully, and then consumed in the titration of aqueous solution of HCl volume and quality of anhydrous Na2CO3, calculate the exact concentration of the HCl solution. Most accurate concentrations of the standard solution are determined by calibration of the method. Constant component in the determination of standard solution concentration range of 0.01 mol • L-1-1 mol • L-1, typically according to the components to be tested to select the height of the size of standard solution concentration. In order to improve the accuracy of calibration, calibration should pay attention to the following points: ? determination of calibration should be parallel 3-4, repeated at least three times, and called for determination of the relative deviation is less than 0.2%. ? in order to reduce measurement error, weighing the baseline amount of substance should not be too few, weighing at least 0.2G above; same titration at the end consumption of standard solutions or too small in size, the best is 20mL. C preparation of calibration solutions and use liquor, such as glassware, such as volumetric flasks and pipettes, where necessary, corrected volume, and considering the effect of temperature. D calibration good of standardOperated by stock solution was prepared solution, in principle only be diluted once, if necessary, dilute the secondary. Dilution of too many accumulated error is too large, affect the accuracy of the results. 2. calibration cannot be directly made accurate concentrations of the standard solution, first solution was prepared, and then select the base material calibration. Do the titration with acid and alkali solution, it is usually prepared with about 0.1mol • The concentration of L-1. Of solid acid and alkali solution prepared from original, generally only accurate to 1~2 significant figures, it can be graduated cylinders measuring liquids or solid reagents weigh in the scales, add the solvent (water), graduated cylinder or measuring cup amounts. But in the whole process of calibration solution, everything is very strict and accurate. Weighing standard substances requires the use of analytical balance, accurate to four digits after the decimal point. Volume calibration solution, if it were to participate in the concentration are calculated using volumetric flasks, pipettes, burets accurate operation, not sloppy. (B) the general solution preparation and preservation methods of 1:1 (or 1+1), 1:2 (1+2) volume is expressed as concentration. For example, 1:1 solution of H2SO4, the original concentrated H2SO4 volume 1 volume, mix with 1 volume of water. And as 1:3 HCl, the original volume 1 volume hydrochloric acid and three volumes of water and mix. Preparation of solution, according to the requirements on the accuracy of solution concentration should be determined on the balance at the level of the weighing; record should be written to several significant figures; the prepared solution choose what kind of vessel. That accurate, it should be very strict tolerances can be less stringent. The "quantity" concept