International audienceUsing incoherent Optical Code Division Multiple Access (OCDMA) technique has recently attracted much interest since it appears to be not only a simple solution to provide user differentiation but also to perform service differentiation. The main limitation usually taken into account in the theoretical performance evaluation is Multiple Access Interference (MAI) linked to the fact that code sequences are unipolar and thus not strictly orthogonal. However, due to MAI and to the fact that the nature of the optical regime is not perfectly incoherent, beat noise constitutes another important limitation. We focus in this paper on multi-weight two dimensional (2-D) code sequences, which permits providing different BER services. We propose a theoretical statistical model to characterize MAI and beat noise impact. Thanks to this model, a theoretical error probability expression is established, taking into account both MAI and beat noise contribution in multimedia OCDMA systems. The design of multimedia codes satisfying targeted BERs can thus be done considering both limitations. The results permit highlighting the importance of beat noise consideration in the design process and the constraints imposed on optical source requirements