PON (Passive optical network) based FTTH access network is a point-to-multipoint, fiber to the premises network architecture in which unpowered optical splitters are used to enable a single optical fiber to serve 32-128 premises. FTTH network exploits the low attenuation and high bandwidth of single-mode fiber to provide many times more bandwidth than currently available with existing broadband technologies.
Optical line terminal, optical splitters and optical network terminal/unit are the three components of FTTH access network
OLT (Optical Line Terminal)
The optical line terminal is the main element of the network and it is usually placed in the local exchange. It is the engine that drives FTTH system. Traffic scheduling, buffer control and bandwidth allocation are the most important functions of optical line terminal. Typically, OLT operates using redundant DC power and has at least 1 Line Card for incoming internet, 1 System Card for on-board configuration, and 1 to many GPON cards. Each GPON card consists of a number of GPON ports.
The optical splitter splits the power of the signal. That is to say, each fiber link entering the splitter may be split into a given number of fibers leaving the splitter. Usually, three or more levels of fibers correspond to two or more levels of splitters. This enables sharing of each fiber by many users. The passive optical splitter has the characteristics of broad operating wavelength range, low insertion loss and uniformity, minimal dimensions, high reliability, and supporting network survivability and protection policy.
ONT/ONU (Optical Network Terminal/Unit)
ONT/ONU is deployed at customer’s premises. It is connected to the OLT by means of optical fiber and no active elements are present in the link. In GPON, the transceiver in the ONT/ONU is the physical connection between the customer premises and the central office OLT.
The basic components of the GPON FTTH access network are presented and the contribution of each component to the architecture of the FTTH network is addressed. GPON FTTH network architecture is indeed reliable, scalable, and secure. It is a passive network, so there are no active components from the CO to the end user, which dramatically minimizes the network maintenance cost and requirements. FTTH is future proof solution for providing broadband services.