我国公用电信网的发展十分迅速，先后建立起了 7个宽带因特网骨干网，整个网络规模已成为世界最大的电信网之一。随着因特网的迅猛发展，网络用户将呈指数型增加。作为公用通信网的重要组成部分——用户接入网已成为网络发展的新瓶颈。目前，各国都在致力于研究接入网的技术， The development of China’s public telecommunication network is very rapid, has set up seven broadband Internet backbone network, the entire network has become the world’s largest telecommunications network. With the rapid development of the Internet, network users will increase exponentially. As an important part of the public communications network - the user access network has become a new bottleneck in the development of the network. At present, all countries are devoted to studying the technology of the access network,