How GPON Works

A GPON network is capable of transmitting ethernet, TDM (Time Division Multiplexing) as well as ATM traffic. A GPON network consists of OLT (Optical Line Terminals), ONU (Optical Network Unit), and a splitter. The splitter will divide the signal when needed. The OLT takes in all of the optical signals in the form of beams of light from ONUs and will convert it to an electrical signal. OLTs normally support up to 72 ports. An ONU connects to end users and will send their signals back to the OLT. A GPON network can reach up to 20 km and provide service up to 64 end users. GPON utilizes both upstream and downstream data by means of Optical Wavelength Division Multiplexing (WDM).

In downstream transmission, the lasers wavelength measures 1490 nm while the upstream wavelength measures 1550 nm. A single mode optical fiber coming from a central office, runs to a passive optical power splitter located near end users’ locations. The optical splitter will then divide power into separate paths which can range from two to sixty four. From the optical splitter, separate single mode fiber strands will run directly to the end user’s home, business, school, etc. This transmission can reach up to 20 km starting from the central office running to the user. With GPON transmitting downstream in a broadcast manner and upstream in a TDMA (time division multiple access) manner, different bit rates are possible with 1.2 Gbit/s in upstream and 2.4 Gbit/s in downstream is most common.