在光纤通信理论中，光纤有单模、多模之分，区别在于：

1. 单模光纤芯径小（10m m左右），仅允许一个模式传输，色散小，工作在长波长（1310nm和1550nm），与光器件的耦合相对困难

2. 多模光纤芯径大（62.5m m或50m m），允许上百个模式传输，色散大，工作在850nm或1310nm。与光器件的耦合相对容易

而对于光端模块来讲，严格的说并没有单模、多模之分。所谓单模、多模模块，指的是光端模块采用的光器件与何种光纤配合能获得最佳传输特性。

一般有以下区别：

1. 单模模块一般采用LD或光谱线较窄的LED作为光源，耦合部件尺寸与单模光纤配合好，使用单模光纤传输时能传输较远距离

2. 多模模块一般采用价格较低的LED作为光源，耦合部件尺寸与多模光纤配合好

 

 

 

 

 

 

 

 

 

 

 

 

 

单模光纤(Single Mode Fiber)：中心玻璃芯很细(芯径一般为9或10μm)，只能传一种模式的光。因此，其模间色散很小，适用于远程通讯，

http://attach.sl.iciba.com/images/thread/de/ae/deae13d7b420e40240804baea3ed0a69.jpg                 http://attach.sl.iciba.com/images/thread/8e/75/8e755b78a458eba7614eb4f6b3f15617.jpg

1．商务写作：

Sales Department
Lang Tong Ltd
45 Haidai Street
Wakon Strict
Beijing China

December 23,2000

Purchasing Department
Fu Rong Supermarket
No. 112, Lan Tian Road
Shanghai, China

Dear Sir,

We are to clear a residue stock of electric equipment of various types, some of which you ordered from us in large quantities previously.
As you are one of our most regular customers, we would like you to share this excellent opportunity first. You may be interested to see from the enclosed price-list that for all the types available we allow you a discount of 20% on the current prices stated.
This is an exceptional opportunity for you to buy a stock of high-quality products at prices we cannot repeat. We hope you will take full advantage of it. The above offer is subject to your reply reaching here before the end of the month.
We are looking forward to your favorable r