Provided is an optical access network capable of realizing protection control without affecting an E-PON for providing an Ethernet service. In the optical access network comprising the E-PON having a transmission line which is duplexed between an OLT and a plurality of ONTs, the OLT includes a layer-2 (L2) control section in which a protocol, in which protection control information is provided, as a protocol structure, above an Ethernet media access control (MAC), is mounted. Further, the OLT has a protocol structure in which the protection control information is provided independently from the Ethernet MAC to transfer user data and the protection control information.