Analyze the technical features of the optical fiber Access Network

The optical fiber access network is worth learning a lot. Here we mainly introduce the technical features of the optical fiber access network. The optical fiber access network refers to the access network with the optical fiber as the transmission medium in the access network. The Optical fiber access Network technology can be divided into two categories: AON and Active Optical Networks and PON and Passive Optical networks ). Active optical networks can be divided into SDH-based AON and PDH-based AON. Passive Optical Networks can be divided into narrowband PON and broadband PON.

Because the optical fiber access network uses optical fiber as the transmission medium, according to the depth of the user base of the optical fiber, the optical fiber access network can be divided into FTTC optical fiber to the roadside), FTTZ optical fiber to the residential area), FTTB optical fiber to the building) FTTO optical fiber to office) and FTTH optical fiber to household), collectively referred to as FTTx. FTTx is not a specific access technology, but the progress or Usage Policy of the optical fiber in the access network.

Technical Features

1. Active Optical Network

As the name suggests, the CE of the local device of the Active Optical Fiber access network and the RE of the remote device are connected through the active optical transmission equipment. The transmission technology is a widely used SDH and PDH Technology in the backbone network, however, SDH technology is the main technology. Remote devices are used to collect, adapt, reuse, and transmit services. Local devices provide interface adaptation, multiplexing, and transmission functions. In addition, local devices also provide network management interfaces to the Network Element Management System. In actual access network construction, the topology of the Active Optical Network is usually star or ring. Active Optical Networks have the following technical features:

◆ Large transmission capacity. SDH transmission devices currently used in access networks generally provide interfaces of 155 Mbit/s or 622 Mbit/s, and some even provide interfaces of 2.5 Gbit/S. In the future, as long as there is sufficient traffic demand, the transmission bandwidth can increase. The transmission bandwidth potential of optical fiber is almost unlimited compared with the access network demand.

◆ The transmission distance is far. The transmission distance can reach 70 ~ 80 km.

◆ User information isolation is good. The network topology of the Active Optical Network is either star or ring. Logically, the transmission mode of user information is point-to-point.

◆ Mature technology: SDH devices and PDH devices have been widely used in Ethernet.

Because SDH/PDH technology is widely used in backbone transmission networks, the cost of active optical access devices has been greatly reduced. However, compared with other access technologies, the cost of access networks is relatively high.

2. ATM Passive Optical Network (ATM-PON)

The most important characteristic of ATM-PON is its passive point to multi-point network structure. It integrates the ATM technology and passive optical network technology, and can provide various services from narrowband to broadband. The ATM-PON is composed of OLT, ONU/ONT and Passive Optical splitter. The Splitter is the optical Splitter. It splits the incoming optical signals and distributes them to multiple optical fibers, or combines them into one optical fiber. ONU/ONT is mainly used to collect, adapt, reuse, and transmit services. OLT is mainly used to adapt, reuse, and transmit interfaces. In addition, the OLT also provides network management interfaces to the Network Element Management System.

The working method of the optical splitter In the ODN optical distribution network is passive, which is the origin of the word "passive" in the passive optical fiber access network. However, the ONU and OLT work in the active mode, that is, the external power supply is required to work normally. Therefore, using the passive optical network access technology, not all devices work without external feeds, but the ODN part does not have any active devices.