The basic structure and advantage analysis of FTTH network.The first thing to know about the concept of FTTH network is that it is an optical fiber directly to the home.Specifically, FTTH cable refers to the optical network unit (ONU) installed in the home user or enterprise user, is the optical access network application type closest to the user except FTTD(fiber to the desktop) in the optical access series.
With the development of science and technology, FTTX technology makes optical fiber more and more close to the end user, and this form will bring greater performance convenience to the user.Every aspect of optical fiber that is superior to copper wire, including bandwidth, rate, data format and transparency of wavelength and protocol, will be directly faced by households and enterprises, and some limitations of copper wire will gradually fade away with the process of "copper withdrawal".
The basic structure and advantage analysis of FTTH network.
A typical EPON system consists of OLT, ONU and ODN:
The OLT is located in the central machine room and can be viewed as an L2 switch or an L3 routing switch.In the downward direction, OLT provides fiber optic interface for ODN.In the upstream direction, the OLT will provide GE lamp power interface, and will support similar high-speed interface when the Ethernet technology standard of 10Gbit/s is finalized in the future.To provide multi-service access, OLT can also support E1 and OC3 interfaces to achieve traditional voice access or circuit relay services.
ODN is an optical distribution network composed of passive fiber branch and fiber.Passive fiber optic branchers are passive devices that connect OLT and ONU to distribute downlink and centralize uplink data.Passive splitters are quite flexible in their deployment.Since it is a passive device, it can adapt to almost all environments.The spectral ratio of passive optical fiber branch is 1:2, 1:4, 1:8, 1:16, 1:32, 1:64 and so on.It is generally recommended to use a first order spectrophotometer, with no more than a second order spectrophotometer.
ONU is a terminal device placed on the user's site. In EPON, ONU adopts Ethernet protocol to realize low-cost Ethernet layer 2 switching function.Since Ethernet protocol is used, protocol conversion is no longer needed in the communication process, realizing transparent transmission of user data by ONU.Encryption protocol is adopted between OLT and ONU to ensure the security of user data.(http://www.aoatech.cn/)