<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> We present an extended theoretical model for time- spreading optical code-division multiple-access (OCDMA) coherent systems. We have updated well-known model to evaluate multiuser interference to include arbitrary encoded/decoded chip shape, receiver transfer function, and optical thresholding before detection. Full asynchronous regime is also assumed to exploit statistical benefits over the dominant primary beat noise. The model provides clear improvements in terms of number of users and required intercodes crosstalk, leading to more feasible OCDMA systems. </para>