The key feature that makes GPON the most commonly adopted solution for FTTH is the fact that the optical network is passive, meaning that there are no powered points between the two ends of the network (exchange and homes). This is a significant advantage of the technology, as it reduces costs and the possibility of failures. While a large city covered by FTTC has hundreds of active devices (ONUs) scattered throughout the streets, with FTTH-GPON, the only elements the operator needs to worry about powering are the exchanges/POPs.
GPON is the technology currently used in Italy to create FTTH networks.
A passive optical network (such as GPON) is of the point-to-multipoint type. The “point” is an operator device (OLT, Optical Line Terminal), which is often found in the local exchange, while the “multipoints” are devices installed inside the customers' homes (ONT or UN, respectively Optical Network Terminal And Optical Network Unit).
In the case of GPON, a single OLT is able to connect a maximum of 128 users for each output fiber optic cable. This number determines the splitting factor (or branching factor, in Italian).
An OLT can have hundreds of ports, each of which forms an optical tree, connected to each end by a number of users equal to the splitting factor. The 2.5/1.25 Gbps speed provided by GPON is shared among all the users connected to the same tree...