SDH系统的光传输距离主要受两个因素的限制:一是();二是()。对于高比特率的传输系统,()是限制中继段传输长度的主要因素。
参考答案:光功率限制;光源的色散限制;色散
完成句子
11.He was so excited that l couldn't make him _____ (平静下来).
12. We are all _________ (相处得很好) each other in our class.
13.She _____ (为....担忧)her son's future.
14.There has been ________ (一系列)cars accidents at the crossing.
15.Filling the blanks ________ (根据)what I have said.
什么是审计?