1 Telecommunication networks and digital subscriber lines
1.4 Hybrid access network

Nowadays it is necessary to provide to subscribers new services than just phone service. Above all, it is a high-speed data transfer and access to the global Internet network, the transmission of television and video signals. Possibilities of metallic access network but nowadays approaching their limits. Physical parameters of twisted pair (attenuation, group velocity of propagation, crosstalks, etc.) significantly reduce transmission parameters such as transfer rate and prevent its further increase. The solution to this situation is to replace the symmetrical pairs in the access network for optical fibers. Given the conventional topology of the access network, however, this solution is too expensive. Therefore, the replacement of copper pairs for optical fibers takes place gradually since the ISP network node towards the end subscriber. Such access network abbreviated FTTx (Fiber to the x), where character x is a wildcard, which indicates the point of termination of the optical fiber. The main types of FTTx networks are:

- FTTH – Fiber To The Home
- FTTO – Fiber To The Office (means to the office or business premises)
- FTTB – Fiber To The Building
- FTTC, FTTCab – Fiber To The Curb, Fiber To The Cabinet (means to a local cabinet or sidewalk column) with a length of copper wire up to 300 m,
- FTTN – Fiber To The Node (to a local hotspot - street cabinet, column) with a length of copper wire over 300 m,
- FTTEx – Fiber To The Exchange (means to the local digital exchanges),
- FTTdb – Fiber To The Distribution Point.

Example of classical metallic access network, hybrid access network based on concept FTTCab and fully optical access network