The access network is the bridge for users to enter the metropolitan area network/backbone network, and is the "last mile" of the information transmission channel. In the past few years, the core part of the network has undergone earth-shaking changes. Both switching and transmission have been updated, and the access network has developed slowly due to economic issues such as user business needs, user density, and user economic affordability, which has become a constraint on the network to broadband and full service. The bottleneck of development. With the rapid development of my country's economy, high-bandwidth consuming services have gradually emerged, and bandwidth acceleration has become an urgent need. In order to meet the needs of users, a variety of new technologies continue to emerge, and access network technology has become the focus and investment focus of equipment manufacturers, operators and telecom research departments.
Among various broadband access technologies, passive optical networks have become popular technologies due to their large capacity, long transmission distance, lower cost, and full service support. At present, the most common passive optical networks that have been commercialized mainly include EPON and GPON. The transmission wavelength used is generally 1490nm for downlink and 1310nm for uplink; 2.5Gbps for downlink and 1.25Gbps for upload. As the demand for efficient transmission of network rates is becoming more and more urgent, some areas have adopted 10G EPON systems, which can reach 10Gbps in the downlink and support up to 10Gbps in the uplink, which greatly improves the transmission of the network rate.
The three main parts of PON (passive optical network) include OLT (Optical Line, Terminal, optical line terminal) at the central office, terminal ONU Optical Network Unit, and ODN (Optical Distribution Network, optical distribution network) ). PON "passive" means that the ODN is all composed of passive components such as optical splitters (Splitter), and does not contain any electronic components and power supplies.
To put it simply, a PON network consists of an optical line terminal (OLT) installed at the central control station, and a batch of matching optical network units (onu) installed at the user site. The optical distribution network (ODN) between the OLT and the ONU contains optical fibers and passive splitters or couplers.