The EPON ONU SFP transceiver is designed for the Optical Network Unit (ONU) in Gigabit Ethernet Passive Optical Networks, supporting symmetrical data rates of 1.25 Gbps for both downstream and upstream transmission. It fully complies with the IEEE 802.3ah EPON standard. Digital diagnostics monitoring (DDM) is implemented via the 2-wire serial bus as specified in the SFP MSA.