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complete temporary tasks assigned by the Manager. Second, characteristic functions 1, according to the company, \bility of three\quirements of the management system, responsible for \bility of three\nd the formulation of major rules and regulations, and is responsible for training, implementation, inspection and guide its operation; 2, the company responsible for the Department (workshop) annual and monthly economic responsibility economic responsibility system and various special formulation, revision, inspection, evaluation, internal evaluation, summary, approved and communicated, audits, surveys, feedback from senior Department assessment; 3, responsible for the company's long-term plan, annual plan of work; 4, is responsible for the company's monthly operating conditions analysis and monthly focus assessment focus; 5 rules and regulations, the company responsible for the development, examination, inspection and training, Discovery Manager. 10 quality accidents of work, the company responsible for the Department of investigation, judge, processing, analysis, summary and reporting; 11, and is responsible for implement implementation implementation national of financial system, and financial discipline, according to company \bility three of\s, developed company financial management and financial supervision system (including funds costs approval system, and borrowing approval system, and settlement system cash management system,), by Manager approved Hou seriously organization implementation, and implementation, and实验一 光纤光学基本知识演示

【实验目的】

通过光纤的预备知识和的具体演示，使实验者对光纤光学有基本的认识，并为后面的实验打下知识基础

【实验仪器】

普通光纤（3米长） 二根（一根为单模光纤，一根为多模光纤） He-Ne激光器及电源 一套 短波光功率计 一只 白纸光屏 一个

【演示实验内容】

[演示一] 如图一所示，取一根长约一米的普通单模光纤，剥去其两端头的套塑和涂敷层，然后将激光耦合进任一端，试观察光纤另一端的输出面发光情况。其中，亮的中心部分为纤芯，外围为包层。对多模光纤可观察到光纤传输模式。

He-Na laser

聚焦透镜 光纤支架 出射光

图一、演示二示意图

[演示二] 如图二实验系统，激光输出的激光束经耦合入光纤后在光纤中传输，然后从另一端射出，用白屏接收光斑，观察其近场图案和远场图案。

聚焦透镜光纤支架激光器光纤支架近场图案远场图案光纤图七、光纤的近场图和远场图 [演示三] 如图三所示实验系统，先让三米长左右的光纤的尽量伸展开，读出并记录下此时光纤的输出光功率值，然后将光纤一圈一圈绕于手上，观察输出光功率随所绕圈数多少和圈半径大小的关系。（注意，光纤不能绕过小圆圈，否则会损伤和折断光纤）

光功率

He-Na

220V交 聚焦透光纤支光纤支探测器短波 图三、演示三示意图

complete temporary tasks assigned by the Manager. Second, characteristic functions 1, according to the company, \bility of three\quirements of the management system, responsible for \bility of three\nd the formulation of majorules and regulations, and is responsible for training, implementation, inspection and guide its operation; 2, the company responsible for the Department (workshop) annual and monthly economic responsibility economic responsibility system and various special formulation, revision, inspection, evaluation, internal evaluation, summary, approved and communicated, audits, surveys, feedback from senior Department assessment; 3, responsible for the company's long-term plan, annual plan of work; 4, is responsible for the company's monthly operating conditions analysis and monthly focus assessment focus; 5 rules and regulations, the company responsible for the development, examination, inspection and training, Discovery Manager. 10 quality accidents of work, the company responsible for the Department of investigation, judge, processing, analysis, summary and reporting; 11, and is responsible for implement implementation implementation national of financial system, and financial discipline, according to company \bility three of\s, developed company financial management and financial supervision system (including funds costs approval system, and borrowing approval system, and settlement system cash management system,), by Manager approved Hou seriously organization implementation, and implementation, and输入光功率固定P0= 弯曲半径 输出光功率 损耗系数（dB）

用matlab拟合出出损耗系数与曲率半径的关系式；

【思考题】

1、根据演示二观测到的近场图案和远场图案，试想可以确定光纤的那些参数？ 2、通过阅读材料，说出减小光纤损耗的途径有那些？

实验二 光纤数值孔径（NA）的性质和测量实验

【实验目的】

１、熟悉光纤数值孔径的定义和物理意义 ２、掌握测量光纤数值孔径的基本方法

【实验原理】

光纤数值孔径（NA）是光纤能接收光辐射角度范围的参数，同时它也是表征光纤和光源、光检测器及其它光纤耦合时的耦合效率的重要参数。图一示出了阶梯多模光纤可接收的光锥范围。因此光纤数值孔径就代表光纤能传输光能的大小，光纤的NA大，传输能量本领大。

自由空间θc接收光锥范围纤芯 NA的定义式是

图一、光纤最大接收角和接收光锥示意图NA?no*Sinθ=

式中no为光纤周围介质的折射率，θ为最大接受角。n1和n2分别为光纤纤芯和包层的折射率。光纤在均匀光场下，其远场功率角分布与理论数值孔径NAm有如下关系：

Sin?????NAm

其中θ是远场辐射角，Ka是比例因子，由下式给出：

?

??1??P(?)/P(0)? 式中P（0）与P（θ）别分θ=0和θ=θ处远场辐射功率，g为光纤折射率分布参数。计算结

2

θmax包层

n?n1222

g/2

complete temporary tasks assigned by the Manager. Second, characteristic functions 1, according to the company, \bility of three\quirements of the management system, responsible for \bility of three\nd the formulation of major rules and regulations, and is responsible for training, implementation, inspection and guide its operation; 2, the company responsible for the Department (workshop) annual and monthly economic responsibility economic responsibility system and various special formulation, revision, inspection, evaluation, internal evaluation, summary, approved and communicated, audits, surveys, feedback from senior Department assessment; 3, responsible for the company's long-term plan, annual plan of work; 4, is responsible for the company's monthly operating conditions analysis and monthly focus assessment focus; 5 rules and regulations, the company responsible for the development, examination, inspection and training, Discovery Manager. 10 quality accidents of work, the company responsible for the Department of investigation, judge, processing, analysis, summary and reporting; 11, and is responsible for implement implementation implementation national of financial system, and financial discipline, according to company \bility three of\s, developed company financial management and financial supervision system (including funds costs approval system, and borrowing approval system, and settlement system cash management system,), by Manager approved Hou seriously organization implementation, and implementation, and 果表明，若取P（θ）/P（0）=5%，在g≥2时Ka的值大于0.975。因此可将对应于P（θ）曲线上光功率下降到中心值的5%处的角度θe的正弦值定义为光纤的数值孔径，称之为有效数值孔径：

NAeff?sin?e

本实验正是根据上述原理和光路可逆原理来进行的。

【实验仪器】

He-Ne激光器及电源、读数旋转台、光纤微调架、毫米尺、白屏、短波长光功率计等。 实验系统图如图1和图2所示。

【实验步骤 】

１、He-Ne激光器和光功率计的电源，调整实验系统； a.调整He-Ne激光管，使激光束平行于实验平台面； b.调整旋转台，使He-Ne激光束通过旋转轴线； c.取待测光纤，一端经旋转台上的光纤微调架与激光束耦合，另一端与光探测器相连； d.仔细调节光纤微调架，使光纤端面准确位于旋转台的旋转轴心线上，并辅助调节旋转台使光纤的输出功率最大。 光纤支架 读数旋转台 待测光纤 He-Na laser 聚焦透镜 观察屏 光功率计 图二、光纤数值孔径的测量(方法一) 光纤支架 读数旋转台 待测光纤 He-Na laser 聚焦透镜 220V交流探测器短波探 图三、光纤数值孔径的测量(方法二)

测输出数值孔径角θo。实验系统图如图1所示。

(1)移开光探测器，固定光纤输出端；

(2)置观察屏于距光纤端面L距离处，则在观察屏上可见光纤输出圆光斑，其直径为D；

(3)利用毫米尺测量L和D的值，得输出孔径角为：

θo=arctan[D/（2L）]

２、测试输入孔径角θi

(1) 光纤输出端于光功率计的探头相连；

(2)旋转读数平台，改变光束入射角，记录不同旋转角度θ下的输出光功率值； (3)出P-θ曲线，取P（θ）下降到中心值的5%时所对应的θ值作为θi。 ３、计算光纤数值孔径。

计算公式为： N．A．= Sin θ （8） 其中θ即上一步骤测得的θo和θi。

４、关He-Ne激光器和光功率计的电源，整理实验仪器，结束实验。

【实验数据和记录】

表（1）方法一 测量所得的实验数据和结果

3