Performance evaluation of asynchronous multi-carrier code division multiple access for next-generation long-reach fibre optic access networks

In this study, the authors evaluate the performance of asynchronous optical multi-carrier code division multiple access (MC-CDMA) for intensity modulated/direct detection systems to be used in next-generation optical access networks. The proposed system employs Gold sequence in frequency-domain to provide asynchronous resource sharing. In long-reach passive optical networks, fibre impairments degradation to the performance of ordinary optical CDMA can be avoided by frequency-domain digital compensation methods in the proposed MC-CDMA. In comparison with orthogonal frequency division multiple access, peak-to-average power ratio in the proposed MC-CDMA is reduced and asynchronous resource sharing is achieved. The performance of the proposed optical MC-CDMA system is analytically evaluated by driving closed-form equations for signal-to-interference plus noise ratio and bit error rate (BER) performances. Furthermore, the simulation results are provided in terms of BER against signal-to-noise ratio in one case and the number of users in another, conditioned on the modulation levels. Finally, the analytical formulation of BER is verified with the help of simulation results.