2ⁿ coding architecture for optical code-division multiple-access

Recent study shows that optical code-division multiple-access (CDMA) networks cannot be evaluated or designed by only considering the performance (i.e., correlation properties) of the optical pseudo-orthogonal codes selected. The structures of optical encoders and decoders are another important factors to consider and are needed to coordinate with the selected optical codes as much as possible. As a result, a "serial" coding architecture for optical CDMA has been introduced. This new architecture is found particularly attractive for ultrafast optical processing and waveguide implementation for the future high-capacity, low-loss, all-optical CDMA networks. Since the optical encoder is made of a serial combination of 2×2 optical switches with n of them being biased to a "mix-split" state, the generated OOC's, so-called 2ⁿ codes, pose with a symmetric delay-distribution property. In this paper, we first experimentally demonstrate the serial coding architecture. Afterwards, some techniques for algebraically constructing 2ⁿ codes of weight 4 are presented.