(Ethernet Passive Optical Network (EPON) is the connection of point-to-multipoint network topology and Ethernet technology. Therefore, it can be regarded as a point-to-multipoint LAN. In the upstream direction (ONU to OLT), EPON is a multipoint-to-point network, and in the downstream direction (OLT to ONU), EPON is a broadcast network. Moreover, the OLT and ONU in EPON are not equal, they belong to the master-slave relationship.)