In pon , the transmission of downlink signal from olt to onu is not complex . usually , the information destined for onus are combined into a multiframe at olt via tdm before reaching the feeder fiber , and then broadcast to each onu via the passive optical demultiplexor . upon receiving the downlink multiframe signal , each onu takes out the part of information for itself only 在無源光網(wǎng)絡(luò)中, olt到onu的下行信號的傳輸過程較為簡單,一般在olt將需要發(fā)送到各onu的信息采用時分復(fù)用的方式組成復(fù)幀送到饋線光纖,通過無源光分路器以廣播的方式發(fā)送到每一個onu , onu收到下行復(fù)幀信號后分別取出屬于自己的那一部分信息。