As the first-generation passive optical networks get accepted as the major access network options and more bandwidth demanding broadband applications emerges, the current 1Gb/s network will face the speed limit soon. In the same time, high efficiency OFDM modulation format is considered to replace the traditional OOK-NRZ to increase the speed in optical communications. In this paper, we will introduce the OFDM modulation format and its advantages in optical communications. Besides, using OFDM in PON network is discussed on its current status and future perspective.