GPON stands for Gigabit Ethernet passive optical network (PON)
It consists of an optical line terminal (OLT) that connects several optical network terminals (ONTs/ONUs)
Each splitter is limited to 25 to ensure at least dedicated 100Mbps bandwidth (as majority of customers are on 100Mbps plan)
If there is 2 PONs in an OLT this is said to be dual leg. Both legs back up each other in case one is down. Traffic can also be directed or redirected from one leg to another remotely