An FTTH access network comprises five areas, which are a core network area, a central office area, a feeder area, a distribution area and a user area/customer premises.
The core network includes the internet service provider ISP equipment, PSTN (public switched telephone network, packet switched or the legacy circuit switched) and cable TV provider equipment.
The main function of the central office is to host the OLT and ODF (optical distribution frame) and provide the necessary powering. Sometimes it might even include some of the components of the core network.
The feeder area extends from ODF in the central office (CO) to the distribution points. These points, usually street cabinets, are called fiber distribution terminals (FDTs) where level-1 splitters usually reside. The feeder cable is usually connected as ring topology starting from a GPON port and terminated into another GPON port as shown in the picture above to provide type B protection.
Distribution cable connects level-1 splitter (inside the FDT) with level-2 splitter. Level-2 splitter is usually hosted in a pole mounted box called fiber access terminal (FAT) usually placed at the entrance of the neighborhood.
In the user area, drop cables are used to connect the level-2 splitter inside the FAT to the subscriber premises. For ease of maintenance, usually an aerial drop cable is terminated at the entrance of the subscriber home with a terminal box (TB), then an indoor drop cable connects the TB to an access terminal box (ATB) residing inside the home. Finally a patch cord connects the ONT to the ATB.