国内传统运营商的城域传输网络以承载话音业务为主,而一些新兴运营商的城域网络则以承载数据业务为主。综合考虑设备的成本、技术的成熟程度、需要承载的业务和可靠性等因素,目前国内各运营商城域传输网络的建设仍以SDH设备为主,运营商在网络节点之间铺设光缆,在每个节点安装SD The metro transport network of the traditional domestic carriers is mainly for carrying voice services, while the metro networks of some emerging operators are mainly for carrying data services. Considering the cost of the equipment, the degree of maturity of the technology, the service to be carried and the reliability, etc., at present, the construction of the transmission network of each operator’s metropolitan area is still dominated by the SDH equipment. The operator paves the optical cable between the network nodes, A node to install SD