问题 多项选择题

与多模光纤传输模式相比,单模光纤的传输特点有()。

A.模间色散很小,适用于远距离传输

B.耦合光能量小,传输频带较宽

C.光纤与光源、光纤与光纤间接口较困难

D.传输设备较便宜

答案

参考答案:A, B, C

解析:本题考查的是有线通信线缆。单模光纤的优点是模间色散很小,传输频带宽,适用于远程通信,每公里带宽可达缺点是芯线细,耦合光能量较小,光纤与光源以及光纤与光纤之间的接口比多模光纤难,单模光纤的传输设备较贵。参见教材P66。

阅读理解

阅读理解

       People in different countries have different ways of doing things. Something that is polite in one

country may be quite impolite in another. In Britain, you mustn't lift (举起) your bowl to your mouth

when you are having some soup. But it's different in China. And in Japan you even needn't worry about

making a noise when you have it. It shows that you are enjoying it. Making a noise is considered as

(被认为) bad manners (举止,礼仪) in Britain. If you are a visitor in Mongolia, what manners do they

wish you to have? They wish you to give a loud "burp" (打嗝) after you finish eating. Burping shows

that you like the food.

       In Britain, you should try not to put your hands on the table when you're having a meal. In Mexico,

however, they hope you keep the hands on the table during a meal. But Arabians consider you must be

very careful with your hands. You mustn't eat with your left hand. Arabians consider it very bad manners

eating with left hands. So, what should you do if you are on a visit in another country? Well, you can ask

the local people to help you or just watch carefully and follow them if you are on a visit in another country.

1. It is impolite to lift your bowl to your mouth when you are having some soup in _________.

A. Britain     

B. China     

C. Japan   

D.Mexico

2. In Mongolia, burping after eating shows that _________.

A. you are rude  

B. you are hungry   

C. you dislike the food

D. you like the food

3. What's the main idea of the passage?

A. People in different countries have different ways of doing things.

B. British people are very polite.

C. You mustn't eat with your left hand.

D. Don't worry about making a noise when you have soup.

解答题