PDH技术应该是光传输技术的鼻祖,它经历了近20年市场风雨的洗礼,应该说到今天还有着旺盛的生命力。在光纤接入领域中,PDH技术仍然扮演着重要的角色。尽管各大运营商总部从网络的维护角度出发,不希望继续使用传统的PDH、而是用SDH直接接入。但是由于PDH价格低廉、安装方便,不占 PDH technology should be the originator of optical transmission technology, it has experienced nearly two decades of market baptism of the market, it should be said that there is still a strong vitality today. PDH technology still plays an important role in the field of optical access. Although major operators headquarters from the network maintenance point of view, do not want to continue to use the traditional PDH, but direct access with SDH. However, due to the low price of PDH, easy installation, does not account for