Increasing the Capacity of Optical CDMA Transmission with Non-Binary Modulation

A.A. Garba, J. Bajcsy, and L.R. Chen (Canada)


Optical CDMA, Modulation Techniques, Channel Capacity.


We explore the benefits of using non-binary signaling for Optical Code Division Multiple Access (OCDMA) systems in comparison to traditionally considered binary OCDMA transmission. In particular, we calculate the information theoretic capacity of optical networks when non-binary CDMA sequences and single-user detection are used. We model the OCDMA system as a discrete memoryless channel and compare the M-ary modulated OCDMA system's capacity to the capacity when binary OCDMA is used. We observe that the use of non-binary OCDMA can lead to more than threefold increase in transmission rates in practice. We present a class of input probability distributions that achieve near-capacity mutual information and show potential noise robustness of such transmission architectures. Finally, we propose a scheme for turbo coded OCDMA network and present its simulated bit error rate (BER) performance.

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