Nowadays, Passive Optical Network (PON) [1][2] has emerged to become the most popular optical access network solution. A PON typically consists of an Optical Line Terminal (OLT) at the central office transmitting optical signals received from the access network to the Internet and vice versa, a Remote Node (RN) demultiplexing downstream optical signals received from the OLT and multiplexing upstream optical signals to the OLT, and a group of Optical Network Units (ONUs) receiving downstream optical signals from the RN and generating upstream optical signals to the RN.