A spectral amplitude coded-optical code division multiplexing time division multiplexing (SAC-OCDM/TDM) passive optical network (PON) for upgrading the traditional TDM PON is proposed. To the best of our knowledge, our work is the first to report on the use of both spectral and orthogonal code domains, which are transparent to optical network unit (ONU) for hybrid PON, in order to upgrade TDM PON seamlessly. The fewer encoder/decoders and cheaper optical source under the conditions of high bite rate and large ONU accommodation make the system cost-effective. A downstream experiment is demonstrated, and the results demonstrate that the proposed system is feasible.