In this paper, we interest on the synthesis of spectral phase OCDMA encoders/decoders based on step chirped Fiber Bragg Gratings to enhance their spectral and temporal efficiency. In this process, we use a real-coded Genetic Algorithm as a synthesis technique. The encoders/decoders are formed by step chirped fiber Bragg gratings with π phase shifts giving rise to bipolar code signatures. In fact, the device structure results from the concatenation of fiber Bragg gratings with different nominal periods and π phase shifts inserted between the gratings to implement the code behavior