A Gigabit Ethernet passive optical network (GE-PON) having a double link structure is disclosed. The GE-PON includes an optical line terminal (OLT), a plurality of optical couplers, and a plurality of optical network units (ONUs). The OLT sets up an active link and a standby link in response to a registration request message received over an optical cable. Each of the ONUs is doubly connected with the OLT via the optical cable and is adapted to transmit the registration request message to the OLT, form the active link with the OLT via the optical cable if it receives an active registration message transmitted from the OLT in response to the registration request message, and form the standby link with the OLT via the optical cable if it receives a standby message from the OLT. The optical couplers are disposed between the OLT and each of the ONUs to doubly interconnect them via different optical cables.