Optical access network, also known as “fiber subscriber loop.” It refers to a set of access connections that use optical transmission or partially share the same network side interface between the service node or the remote module and the user equipment.
Optical access network (OAN) refers to the use of optical fiber as the main transmission medium to realize the information transmission function of the access network. It is connected to the service node through an optical line terminal (OLT) and connected to the user through an optical network unit (ONU). The optical access network includes remote devices – optical network units and central office devices – optical line terminals that are connected by transmission devices.
The role of the OLT is to provide an interface between the access network and the local switch, and communicate with the optical network unit of the client through optical transmission. It completely separates the switching function of the switch from user access. The optical line terminal provides maintenance and monitoring for itself and the user. It can be placed directly at the exchange or with the local switch at the remote end.
The role of the ONU is to provide a user-side interface to the access network. It can be connected to a variety of user terminals, with photoelectric conversion and corresponding maintenance and monitoring functions. The main function of the ONU is to terminate the fiber from the OLT, process the optical signal and provide business interfaces for multiple small businesses, business users and residential users. The network side of the ONU is an optical interface, and the user end is an electrical interface. Therefore, the ONU has optical/electrical and electrical/optical conversion functions. It also has the digital/analog and analog/digital conversion functions of the dialogue. The ONU is usually placed closer to the user and has a great deal of flexibility.
1. the network coverage radius is generally small, and no repeater can be needed. However, due to the sharing of optical power or wavelength distribution caused by many users sharing optical fibers, it may be necessary to use a fiber amplifier for power compensation;
2. it is required to meet the transmission of various broadband services, and the transmission quality is good and the reliability is high;
3. the application range of the fiber access network is broad;
4. the investment cost is large, the network management is complicated, and the remote power supply is difficult.