一.引言 网络技术的革命从其底层的物理层技术已经历了三个阶段。第一阶段为基于铜线和微波无线电技术的网络,它出现于光纤技术之前,全部采用电设备。第二代网络已经采用了光纤传输技术的一些优点,比如激光二级管和光学元件的高速度,以及光的低损耗和色散。这些网络的特点是部分或全部的用石英光纤来替代铜线的点到点的链路,由此改善了一些性能参数,比如高的数据 I. INTRODUCTION The revolution in network technology has gone through three stages from the underlying physical layer technology. The first phase was a network based on copper wire and microwave radio technology, which appeared before the fiber optic technology, all using electrical equipment. Second Generation networks have taken advantage of the advantages of optical fiber transmission technologies such as the high speed of laser diodes and optics, as well as the low loss and dispersion of light. These networks are characterized by some or all of the point-to-point links that replace quartz copper with quartz fiber, thereby improving some performance parameters such as high data