Extended perfect difference codes for SAC optical CDMA PONs

In this letter, we present a new code family named the extended perfect difference codes (EPDC) suitable for passive optical network (PON) using compact SAC OCDMA encoder and decoder. Applying a mapping technique, we construct the EPDC, which not only still retain the cyclic property but also can provide flexible code length. Because of the cyclic property, the optical line terminal (OLT) needs only one arrayed waveguide grating (AWG) router to generate each user's codeword effectively. In addition, the decoder in each optical network unit (ONU) using fiber Bragg gratings (FBGs) and the EPDC is also designed. We analyze the system performance with the consideration of phase- induced intensity noise (PIIN) and thermal noise. The numerical result shows that the proposed code has higher transmission capacity than other SAC OCDMA codes.