A Passive Optical Network (PON) is a system that transmits all or most of the fiber cabling and signals to end-users. Depending on where the PON terminal is located, the system can be described as fiber-to-the-curb (FTTC), fiber-to-the-building (FTTB), or fiber-to-the-home (FTTH).

The optical distribution network does not contain any electronic devices and electronic power supply, ODN splitter consist of the passive components, and other components do not require expensive active electronic devices. A passive optical network includes an optical line terminal (OLT) installed at a central control station and a set of optical network units (ONUs) installed at customer side. The Optical Distribution Network (ODN) between the OLT and the ONU contains optical fibers as well as passive optical splitters or couplers.

The structure of the PON system is mainly composed of an Optical Line Terminal (OLT) at the carrier’s office, an Optical Distribution Network (ODN) including passive optical components, an ONU (Optical Network Unit / ONT (Optical Network Terminal). The difference is that the ONT is directly located at the user end, and there are other networks between the ONU and the user, such as Ethernet) and the network element management system (EMS), and usually adopts point-to-multipoint Tree topology.

Fiber is so cheap and easy to use, so FTTx (Fiber To The X, fiber access) as a new generation of broadband solutions are widely used to provide users with high-bandwidth, full-service access platform. The FTTH (Fiber To The Home, FTTH, the fiber is directly connected to the user’s home) is also known as the best business transparent network, is the ultimate way of access network development.

The FTTx is how to work? In many kinds of schemes, PON (Passive Optical Network) is the best choice. PON is an optical distribution network (ODN) which is applied to an access network, an OLT and a plurality of client devices (ONU / ONT) through passive optical cables, optical splitters/combiners, etc., Connecting network. As shown on the right. Both the ONU and the ONT belong to the user equipment. The difference between them lies in that the ONT is located directly on the user end, and there are other networks between the ONU and the user, such as Ethernet.

The key point of “passive” is that the ODN between the OLT and the ONU is an optical access network without any active electronic equipment. Because of this “passive” feature, the purely PON network can avoid electromagnetic Interference and lightning effects reduce line and external device failure rates, improve system reliability, and reduce maintenance costs.

PON technology began to develop in the 1990s, ITU (International Telecommunication Union) started from APON (155 M), developed BPON (622 M), and to GPON (2.5 G); meanwhile, in this century, due to Ethernet technology widespread application, IEEE also developed EPON technology in Ethernet technology. At present, PON technologies for broadband access mainly include EPON and GPON, and the two adopt different standards. The future development is higher bandwidth, such as EPON / GPON technology has developed 10G EPON / 10G GPON, the bandwidth has been a higher upgrade.