PON is a point-to-multipoint optical fiber access technology, including ATM PON, broadband PON, Gigabit PON and Ethernet PON, consisting of OLT (Optical Line Terminal) at the central office, ONU (Optical Network Unit) at the user side, and ODN (Optical Distribution Network) optical network system is a main technology of FTTX. EPON / Gpon is the current mainstream market demand.