Advanced Techniques to Increase the Number of Users and Bit Rate in OCDMA Networks

Optical code-division multiple-access (OCDMA) systems have recently become a topic of interest for their potential application in access points and optical LANs. In this paper, we review OCDMA systems and their limitations, as well as various experimental techniques to increase the number of users and/or bit rate in a system or a network. These techniques include incorporating M-ary modulation formats, hard-limiting receiver, variable thresholding, and orthogonal polarizations as the third dimension. We also discuss some network limitations such as congestion collapse and near-far effect, and we investigate two techniques to overcome them: interference avoidance and missing chip detection.