Dual-threshold sequential detection code synchronization for an optical CDMA network in the presence of multi-user interference

The paper examines the acquisition performance of a synchronization system for an optical fiber-based code-division multiple-access (CDMA) network that employs a dual-threshold sequential detector. The noncoherent optical CDMA network operates asynchronously and optical orthogonal codes (OOCs) are used for the spreading sequences. The performance measure of the synchronizer, the mean acquisition time, is derived via the Markov flow-graph method and Monte Carlo simulations are used to obtain the statistical parameters of the synchronizer when used within the system. The model takes into account the number of active users, the multi-user interference (MUI), the receiver noise and the coupler losses within the network. The results show that by adjusting both the acceptance and rejection thresholds of the sequential detector, the mean acquisition time ran be optimized. The degradation in the synchronizer performance, when the number of active users is changed from the number the synchronizer is designed for, is also assessed.