FTTH (Fiber-to-the-Home) system is the most common type of technology used in optical access networks, especially in the widespread application of broadband optical access networks. It enables full-fiber access to the network for numerous household users, providing access to various narrowband and broadband telecommunication services.
In public telecommunications transit networks, which includes core networks and access networks, FTTH is a form of access network. Therefore, the FTTH system is the access network, meaning it is positioned between the business node interface and the user network interface. These two interfaces define its position in the entire communication network.
Functional components
According to the system's functions in the standard, FTTH system's functional components include three main parts: FTTH Optical Line Terminal (OLT), distribution network, and FTTH Optical Network Terminal (ONT). The standard provides a functional reference model for OAN, which is also applicable to FTTH systems.
Function of components
In FTTH systems, OLT provides the interface on the core network side and connects to one or more DN. DN is the optical distribution network between OLT and ONU; ONU/ONT provides the user-side interface and connects to one or more DN. OLT is placed in the communication bureau, while ONU/ONT is placed in the communication user's home. DN can use active or passive networks. The difference between active and passive networks is that the method of distributing light signals is based on either active electronic devices or passive optical devices. Passive DN has the characteristics of strong environmental adaptation, no power supply, and maintenance. It is widely used in engineering, also known as intelligent optical distribution networks. However, when using a passive optical splitter, the transmission distance will be limited by the optical power budget.
The difference between ONU and ONT is that their UN-side interfaces are different, and ONT can be directly connected to the user terminal, while ONU needs to add adaptation functions to connect to the user terminal. The adaptation function can adapt to xDSL interfaces, Ethernet interfaces, etc.
FTTH system topology
FTTH topology refers to the network topology consisting of central office equipment, DN, and user terminal equipment. Based on the optical interface on the central office access network side corresponding to the user-side optical interface, FTTH network's basic topology can be point-to-point, star, tree, bus, and ring, as well as other types and limited combinations of the basic types, such as ring-shaped star.
The performance indicators of the FTTH system include network performance indicators and business performance indicators. Therefore, the standard sets out the performance indicators for voice services, network performance indicators for cable television signals, network performance indicators based on IP, network performance indicators based on Ethernet, and reliability and availability indicators for the system.
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