问题 问答题 简答题

请简述DCM色散补偿模块在G.652光纤中进行补偿的几种种方案。

答案

参考答案:

1)置于发送端的OBA与OMU之间,此时发送端的OMU采用介质膜滤波器型。此方案为预补偿

2)在接收端采用OPA+DCM进行后补偿

3)置于线路中,DCM插在OLA放大前面,采用DCM+OLA作为放大站。

4)对于32×10Gb/s系统,当OTM收端前级线路插损<12dB时,无须配置OPA板但是需要配置SDMR板,可在接收端采用SDMR+DCM进行后补偿

5)置于线路中,采用OPA+DCM+OBA两级放大作为放大站。此方案既可做后补偿,亦可做前补偿。

6)在OADM站点,采用OPA+OBA两级放大,中间插DCM的方法

阅读理解

阅读理解。

     Up to 65% of children don't get as much sleep as they should do, and this can make them nervous

and slower at school, scientists say.

     So how long should young people sleep each night? The answer is between eight and ten hours. If

you don't get enough sleep at night, you'll have less energy the next day.

     But the scientists say many children have missed out on 4,500 hours of sleep by the time they are

seven years old. They say that children miss sleep because they have TVs and computers in their rooms,

and busy parents don't read to their younger children at night any more. The traditional "bedtime story"

helps children to relax and fall asleep peacefully. Children with TVs and computers in their bedrooms

were more likely to sleep badly, and to get less than eight hours' sleep. Even losing one hour's sleep a

night can mean that children do less well at school.

    German scientists think that your brain (大脑) keeps working while you are asleep. To show that

they were right, they gave two groups of people a problem to work out. One group went to sleep, and

the other group stayed awake. The result? The people who slept worked out the answer more quickly.

This showed that their brains had been trying to find the answer while the people were asleep. So,

make sure you get enough sleep tonight, and you'll be at your best tonight , and you'll be at your best

tomorrow!

1. What problem do more than a half of students have?

A. They don't get on well with their studies.  

B. They don't  have enough sleep at night.

C. They don't relax themselves at school.    

D. They don't follow their school rules

2. If you have less energy the next day, you'll probably feel _______.

A. sleepy, slow and nervous            

B. tried, bored and worried

C. afraid, alone and angry              

D. dull, lazy and crazy

3. According to the third paragraph, what has worst influenced many children's sleep?

A. Their parents' noise.                  

B. Bedtime stories.  

C. Too much homework                  

D. TV and computers

4. The German scientists' experiment showed that _______.

A. our study depends on our sleep          

B. our sleep helps improve our health

C. our brain works while we sleep          

D. our brain works faster during sleep

5. This passage in mainly written for _______.

A. parents      

B. school teachers      

C. scientists    

D. young students

单项选择题