We have provided the Internet data service for more than 30 million users over broadband network in Korea. At emerging time of introducing Internet data service, downstream data rate was a critical issue. But nowadays, the key issue is not provided the best effort service but guaranteed bandwidth service. PON system can guarantee the both points. In this paper we present the requirement of EPON system for Fiber to The Pole (FTTP) and Fiber to the Home (FTTH). And then we will show some examples of EPON deployment at KT.