Novel methods for extending optical code set for coherent OCDMA

Abstract

Compared with that used in incoherent system, the optical code (OC) for coherent OCDMA system is analyzed in definition, characters, correlation performances and construction method. Aperiodic correlation property of OC is newly defined, and made the criterion for the judgment of OC' performance in a coherent OCDMA system. A novel differential algorithm is firstly proposed for extending OC set with optimal aperiodic auto-correlation property. With such algorithm ten iterative shows that global aperiodic auto-correlation property and capacity are respectively twice and 3713 bigger than original 127-chip Gold sequence. In order to obtain targeted user number's codes in a finite code set with optimal aperiodic cross-correlation property of OC, a novel cross searching algorithm is firstly given. As an example, 49 codes with good aperiodic cross-correlation property (>22) and aperiodic auto-correlation property (>40) are selected from 129 Gold codes. © 2012 Springer Science+Business Media B.V.