This paper investigates the Optical Serial Interference Cancellation (Opt-SIC) techniques for an Optical Code Division Multiple Access system. A theoretical study has been performed and has lead to an analytic expression of error probability. From numerical calculation and simulation, the performance of both techniques have been studied and compared to the conventional correlation method. We have shown that the Opt-SIC receivers manage to upgrade the performance by choosing the best code parameters and the optimized threshold values.