通信人家园
标题:
求助OTDR资料
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时间:
2007-5-31 15:26
作者:
yymtv
标题:
求助OTDR资料
<p>各位大虾好：</p><p> 小弟是学通信工程专业的，毕设抽到基于<font color="#ff0000">OTDR</font>的光缆网自动监测系统，</p><p>下了一些OTDR的仿真软件，但是缺少相关的资料，想请教大家有没有一些</p><p><font color="#f73809">OTDR</font>的资料，像<font color="#ff0000">.SOR</font>文件什么的。</p><p>紧急求助了！！！！</p><p>不胜感激</p>
时间:
2007-5-31 16:22
作者:
饿了就吃包子
<p>很简单的，现在OTDR都能远端操控的啊</p>
时间:
2007-5-31 22:31
作者:
yymtv
<p>问题在于我这根本没有设备啊</p><p>导师只是叫我做仿真</p><p>又没有相关的资料，LS的大虾帮帮忙吧</p>
时间:
2007-6-2 22:55
作者:
yymtv
<p>事情紧急</p><p>求助各位大虾了</p>
时间:
2007-6-10 23:06
作者:
唐萧
我有OTDR软件！请联系我吧wenjiang886@163.com
时间:
2007-6-11 14:09
作者:
ahowei
没有 来帮顶
时间:
2007-6-22 23:32
作者:
artbuchwald
<p>哈哈 我以前都有的 现在没有了</p><p>爱莫能助了</p>
时间:
2007-6-23 20:51
作者:
artbuchwald
<p class="MsoNormal" align="center" style="MARGIN: 0cm 0cm 0pt; TEXT-ALIGN: center;"><p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt;"><font size="5"><span lang="EN-US"><font face="Times New Roman">OTDR</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">中测试仪表中的几个参数</span></font></p></p><h3 style="MARGIN: 13pt 0cm;"><font size="5"><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";"></span></font><b style="mso-bidi-font-weight: normal;"><font size="3"><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">测试距离、脉冲宽度、折射率、测试光波长、平均值、动态范围、死区、“鬼影”</span></font></b></h3><h3 style="MARGIN: 13pt 0cm;"><b style="mso-bidi-font-weight: normal;"><font size="3"><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";"></span></font></b><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";"><font size="3">下面简单介绍上面各个参数（术语）代表的意义</font></span></h3><h3 style="MARGIN: 13pt 0cm;"><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";"></span><font size="3"><span style="COLOR: red; FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">测试距离</span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">：由于光纤制造以后其折射率基本不变，这样光在光纤中的传播速度就不变，这样测试距离和时间就是一致的，实际上测试距离就是光在光纤中的传播速度乘上传播时间，对测试距离的选取就是对测试采样起始和终止时间的选取。测量时选取适当的测试距离可以生成比较全面的轨迹图，对有效的分析光纤的特性有很好的帮助，通常根据经验，选取整条光路长度的</span><span lang="EN-US"><font face="Times New Roman">1.5</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">－</span><span lang="EN-US"><font face="Times New Roman">2</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">倍之间最为合适。</span></font></h3><p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt;"><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";"><font size="3">从发射脉冲到接收到反射脉冲所用的时间，再确定光在光纤中的传播速度，就可以计算出距离。以下公式说明测量距离</font></span></p><p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 21pt;"><font size="3"><span lang="EN-US"><font face="Times New Roman">c</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">：光在真空的速度</span></font></p><p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 21pt;"><font size="3"><span lang="EN-US"><font face="Times New Roman">t</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">：脉冲发射到接收的总体时间（双程）</span></font></p><p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt; TEXT-INDENT: 21pt;"><font size="3"><span lang="EN-US"><font face="Times New Roman">IOR</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">：光纤的折射率</span></font></p><p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt;"><span lang="EN-US"><p><font face="Times New Roman" size="3"> </font></p></span></p><p><font face="Times New Roman" size="3"> </font></p><font size="3"><span style="COLOR: red; FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">脉冲宽度：</span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">可以用时间表示，也可以用长度表示，很明显，在光功率大小恒定的情况下，脉冲宽度的大小直接影响着光的能量的大小，光脉冲越长光的能量就越大。同时脉冲宽度的大小也直接影响着测试死区的大小，也就决定了两个可辨别事件之间的最短距离，即分辨率。显然，脉冲宽度越小，分辨率越高，脉冲宽度越大分辨率越低。如图所示：</span></font><p></p><p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt;"><font size="3"><span style="COLOR: red; FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">折射率</span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">就是待测光纤实际的折射率，这个数值由待测光纤的生产厂家给出，单模石英光纤的折射率大约在</span><span lang="EN-US"><font face="Times New Roman">1.4</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">－</span><span lang="EN-US"><font face="Times New Roman">1.6</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">之间。越精确的折射率对提高测量距离的精度越有帮助。<span style="COLOR: red;">这个问题对配置光路由也有实际的指导意义，实际上，在配置光路由的时候应该选取折射率相同或相近的光纤进行配置，尽量减少不同折射率的光纤芯连接在一起形成一条非单一折射率的光路。</span></span><span lang="EN-US" style="COLOR: red;"><p></p></span></font></p><p></p><p></p><p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt;"><span lang="EN-US" style="COLOR: red;"><p><font face="Times New Roman" size="3"> </font></p></span></p><p><font face="Times New Roman" size="3"> </font></p><font size="3"><span style="COLOR: red; FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">测试光波长</span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">的就是指</span><span lang="EN-US"><font face="Times New Roman">OTDR</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">激光器发射的激光的波长，波长越短，瑞利散射的光功率就越强，在</span><span lang="EN-US"><font face="Times New Roman">OTDR </font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">的接收段产生的轨迹图就越高，所以</span><span lang="EN-US"><font face="Times New Roman">1310</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">的脉冲产生的瑞利散射的轨迹图样就要比</span><span lang="EN-US"><font face="Times New Roman">1550nm</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">产生的图样要高。但是在长距离测试时，由于</span><span lang="EN-US"><font face="Times New Roman">1310nm</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">衰耗较大，激光器发出的激光脉冲在待测光纤的末端会变得很微弱，这样受噪声影响较大，形成的轨迹图就不理想，宜采用</span><span lang="EN-US"><font face="Times New Roman">1550nm</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">作为测试波长。在高波长区（</span><span lang="EN-US"><font face="Times New Roman">1500nm</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">以上），瑞利散射会持续减少，但是一个红外线衰减（或吸收）就会产生，因此</span><span lang="EN-US"><font face="Times New Roman">1550nm</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">就是一个衰减最低的波长，因此适合长距离通信。所以在长距离测试的时候适合选取</span><span lang="EN-US"><font face="Times New Roman">1550nm</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">作为测试波长，而普通的短距离测试选取</span><span lang="EN-US"><font face="Times New Roman">1310nm</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">为宜，视具体情况而定。</span></font><p></p><p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt;"><span lang="EN-US"><p><font face="Times New Roman" size="3"> </font></p></span></p><p><font face="Times New Roman" size="3"> </font></p><font size="3"><span style="COLOR: red; FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">平均值：</span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">是为了在</span><span lang="EN-US"><font face="Times New Roman">OTDR</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">形成良好的显示图样，根据用户需要动态的或非动态的显示光纤状况而设定的参数。由于测试中受噪声的影响，光纤中某一点的瑞利散射功率是一个随机过程，要确知该点的一般情况，减少接收器固有的随机噪声的影响，需要求其在某一段测试时间的平均值。根据需要设定该值，如果要求实时掌握光纤的情况，那么就需要设定平均值时间为</span><span lang="EN-US"><font face="Times New Roman">0</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">，而看一条永久光路，则可以用无限时间。</span></font><p></p><p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt;"><span lang="EN-US"><p><font face="Times New Roman" size="3"> </font></p></span></p><p><font face="Times New Roman" size="3"> </font></p><font size="3"><span style="COLOR: red; FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">动态范围</span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">：它表示后向散射开始与噪声峰值间的功率损耗比。它决定了</span><span lang="EN-US"><font face="Times New Roman">OTDR</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">所能测得的最长光纤距离。如果</span><span lang="EN-US"><font face="Times New Roman">OTDR</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">的动态范围较小，而待测光纤具有较高的损耗，则远端可能会消失在噪声中。目前有两种定义动态范围的方法：</span></font><p></p><p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt;"><span lang="EN-US" style="mso-fareast-font-family: "Times New Roman";"><span style="mso-list: Ignore;"><font face="Times New Roman"><font size="3">1、</font><span style="FONT: 7pt "Times New Roman";"> </span></font></span></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";"><font size="3">峰值法：它测到噪声的峰值，当散射功率达到噪声峰值即认为不可见。</font></span></p><p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l0 level1 lfo1; tab-stops: list 18.0pt;"><font face="Times New Roman"><span lang="EN-US" style="mso-fareast-font-family: "Times New Roman";"><span style="mso-list: Ignore;"><font size="3">2、</font><span style="FONT: 7pt "Times New Roman";"> </span></span></span><span lang="EN-US"><font size="3">SNR=1</font></span></font><font size="3"><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">法：这里动态范围测到噪声的</span><span lang="EN-US" style="COLOR: red;"><font face="Times New Roman">rms</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">电平为止，对于同样性能的</span><span lang="EN-US"><font face="Times New Roman">OTDR</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">来讲，其指标高于峰值定义大约</span><span lang="EN-US"><font face="Times New Roman">2.0db</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">。（图）</span></font></p><p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt 18pt;"><font size="3"><span style="COLOR: red; FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">后向散射系数</span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">：如果连接的两条光纤的后向散射系数不同，就很有可能在</span><span lang="EN-US"><font face="Times New Roman">OTDR</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">上出现被测光纤是一个增益器的现象，这是由于连接点的后端散射系数大于前端散射系数，导致连接点后端反射回来的光功率反而高于前面反射回的光功率的缘故。遇到这种情况，建议大家用双向测试平均趣值的办法来对该光纤进行测量。</span></font></p><p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt;"><span lang="EN-US"><p><font face="Times New Roman" size="3"> </font></p></span></p><p><font face="Times New Roman" size="3"> </font></p><font size="3"><span style="COLOR: red; FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">死区</span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">：死区的产生是由于反射淹没散射并且使得接收器饱和引起，通常分为衰减死区和事件死区两种情况。</span></font><p></p><p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l1 level1 lfo2; tab-stops: list 18.0pt;"><span lang="EN-US" style="mso-fareast-font-family: "Times New Roman";"><span style="mso-list: Ignore;"><font face="Times New Roman"><font size="3">1、</font><span style="FONT: 7pt "Times New Roman";"> </span></font></span></span><font size="3"><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">衰减死区：从反射点开始到接收点回复到后向散射电平约</span><span lang="EN-US"><font face="Times New Roman">0.5db</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">范围内的这段距离。这是</span><span lang="EN-US"><font face="Times New Roman">OTDR</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">能够再次测试衰减和损耗的点。</span></font></p><p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt 18pt; TEXT-INDENT: -18pt; mso-list: l1 level1 lfo2; tab-stops: list 18.0pt;"><span lang="EN-US" style="mso-fareast-font-family: "Times New Roman";"><span style="mso-list: Ignore;"><font face="Times New Roman"><font size="3">2、</font><span style="FONT: 7pt "Times New Roman";"> </span></font></span></span><font size="3"><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">事件死区：从</span><span lang="EN-US"><font face="Times New Roman">OTDR</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">接收到的反射点开始到</span><span lang="EN-US"><font face="Times New Roman">OTDR</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">恢复的最高反射点</span><span lang="EN-US"><font face="Times New Roman">1.5db</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">一下的这段距离，这里可以看到是否存在第二个反射点，但是不能测试衰减和损耗。如图所示</span></font></p><p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt 18pt;"><font size="3"><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">鬼影：它是由于光在较短的光纤中，到达光纤末端</span><span lang="EN-US"><font face="Times New Roman">B</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">产生反射，反射光功率仍然很强，在回程中遇到第一个活动接头</span><span lang="EN-US"><font face="Times New Roman">A</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">，一部分光重新反射回</span><span lang="EN-US"><font face="Times New Roman">B</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">，这部分光到达</span><span lang="EN-US"><font face="Times New Roman">B</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">点以后，在</span><span lang="EN-US"><font face="Times New Roman">B</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">点再次反射回</span><span lang="EN-US"><font face="Times New Roman">OTDR</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">，这样在</span><span lang="EN-US"><font face="Times New Roman">OTDR</font></span><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">形成的轨迹图中会发现在噪声区域出现了一个反射现象。如下图所示（红色为一次反射，绿色为二次反射）：</span></font></p><p style="MARGIN: 0cm 0cm 0pt 18pt;"><font size="3"><span style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman";">的突然跌落.</span></font></p>
时间:
2007-6-25 11:36
作者:
阿皮
<p>不是太明白说的是什么？</p>
时间:
2007-8-29 11:03
作者:
doudouch
<p>好像有那么点明白了，有图看就更好了</p><p></p>
时间:
2007-8-31 12:59
作者:
阿皮
你邮箱多少？我这里有一些
时间:
2008-3-14 22:11
作者:
orange33
<p>我的邮箱;hy_chenzhi@163.com,联系我.传些给你吧,每个月我们都有要测</p>
时间:
2008-6-16 15:13
作者:
卡罗维拉
小第也想学习一下,谢谢
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