Optical transmission is getting more popular in the access network due to the increasing demand for bandwidth. This paper introduces an overview of Wavelength-Division-Multiplexed Passive Optical Network (WDM-PON) technology and Time- Division Multiplexing Passive Optical Network (TDM-PON) as well as different passive optical network architectures such as Gigabit PON (GPON), Broadband PON (BPON) and Ethernet PON (EPON).The advantages and disadvantages of each PON architecture is shown in this paper and the comparative results are provided.