After successful application of CDMA techniques in wireless communications, optical CDMA has been considered as a candidate for future access networks. We will focus on passive optical networks (PONs) in particular. This work pursues three main goals: First, due to the depth and extension of the topic, offer a comprehensive overview. Several classes of optical codes are reviewed and different technologies for implementing codes are described and compared. Second, provide some guidelines in order to facilitate the design of OCDMA-based PONs. Since OCDMA allows flexible network design, different approaches can be considered. Finally, outline a possible solution, discussing and analyzing key issues as optical coding and encoding/decoding hardware. System performance or network architecture are also studied.