The optical distribution network (ODN) extends between the optical line termination( OLT) and the optical network unit( ONU), which in the case of Fiber to the Home ( FTTH), for example, is located in the customer's company building.
In the optical distribution network, data is transmitted bidirectionally via optical media and optical components. Monomode fibers are usually used as optical media, transmitting data from downstream users over different wavelengths. GPON and 10GEPON are used in the optical access networks. Optical splitters provide point-to-multipoint connectivity.
In the optical access networks, the optical line termination (OLT) and the optical network unit (ONU) are interconnected by an optical fiber; the maximum distance between the two units is about 20 km.