问题 问答题 简答题

光浪涌现象是如何产生的,说明中兴公司的DWDM设备是如何消除光浪涌现象的。

答案

参考答案:

当光路正常时,由泵浦光激励的饵粒子被信号光带走,从而完成信号光的放大。但是如果此时由于某种原因截断了信号光的输入,而泵浦光源继续将饵离子泵到亚稳态,从而使处于亚稳态的饵粒子越来越多。如果这时候有信号光输入,则将产生能量跳变,产生光浪涌。

解决这一问题的方法是设法在系统中加装光浪涌保护装置。中兴公司的波分复用系统采用了自动光功率减小(APR)的方式来防止浪涌。

启用自动APR功能后,如果下游信号光由于某种原因中断,则根据监控光通道反馈的信号,自动减少或者截断泵浦光源。以消除光浪涌。

阅读理解

阅读短文,根据其内容回答问题。

        Many people always say that listening to spoken English is too hard for them. But if you don't

understand what people are saying, how can you talk with them? It may be difficult, but learning by

listening is necessary. It can be done.

        As we know, different people have different pronunciations of the same word. Standard (标准)

pronunciation is important for English speaking as well as for listening. In China, people from one area

may not understand what people from another area are saying because of the different Chinese dialects

(方言). Standard Chinese pronunciation can help people from different places understand each other easily. 

        It is the same with English. If your pronunciation is not standard, it is as hard for other people to

understand you as it is for you to understand them.

        If you want to learn how to listen to English, the following ways are helpful.

        Get some good books with tapes. Do the exercises, from the simple to the difficult, step by step.

        You can also watch English-language films, listen to English-language radio and TV programmes.

        Try to listen every day, even if only for a few minutes. At first you may understand few words.

Don't give up. Just listen.

        Remember to red and speak English every day. It will help you a lot. Every day, spend an hour

reading English. Finally you will notice that you're making progress.

        Talk to English-speaking people as often as possible. They will speak more slowly with you, use

simple words and use body language to help you understand them. Don't be afraid to talk to them. They

won't mind because they may have more trouble to make themselves understood in Chinese.

1. Is it possible for people to learn English by listening?

    ________________________________________________

2. What do you have to do when you talk with English-speaking people?

    ________________________________________________

3. Why is standard English very important?

    ________________________________________________

4. How many ways does the writer talk about to practise listening?

    ________________________________________________

5. When do you feel easier to understand English-speaking people?

    ________________________________________________

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