ng deployed fibers) as well as of the number of optical-electronic conversions Central office (CO) Fiber Fiber Passive splitter FTTB/C Copper Fiber (G.fast) Up to 0.25 km FTTCab Copper Fiber (VDSL2) Up to 1.5 km Access network (up to 20 km) FTTH - Fiber to the home ONT - Optical network termination FTTCab - Fiber to the cabinet ONU - Optical network unit FTTB/C - Fiber to the building/curb NT - Network termination OLT - Optical line termination VDSL - Very high bitrate digital subscriber line Figure 4.3 FTTx network architecture. 4.2 Ultra-Broadband Optical Access on the way of the signals. All data processing, including buffering, scheduling, etc., at network nodes is done in the electronic domain, while transmission is carried over fiber. In FTTx network architecture electronics is located in the optical line termination (OLT) on the telecom operator's side and in the optical network termination (ONT) on the end-user's side (where the optical link ends, in the home, cabinet, etc.). In the case of FTTC, the termination node is the optical network unit (ONU). The difference between ONT and ONU disappeared over time, SO they will be used interchangeably. Depending whether the fiber architecture is point-to-point or point-to-multipoint (P2MP), four basic architectures for the FTTx access network can be distinguished, which are also referred to as the optical distribution network (ODN): Point-to-point architecture. It uses a separate fiber link between the telecom opera- tor and the user's home. So, the number of fiber links needed in this case equals the number of homes being connected. Obviously this architecture can provide maxi- mum capacity because there is dedicated optical cable per home; however, it is the least cost-effective. Passive optical network architecture. This is P2MP architecture which uses a shared fiber link between the OLT and passive splitters toward the ONTs on the end-user's side (they perform signal splitting in the optical domain, without any electric power connection to the unit) between 