Frame Time Hopping Patterns for Optical CDMA.

Frame Time Hopping Patterns for Optical CDMA.

Abstract

In this talk, we introduce a new spreading technique for intensity modulation direct detection Fiber-Optic-Code-Division Multiple-Access (FO-CDMA) communication systems. These codes are a class of Optical Orthogonal Codes (OOC's) which have an extremely large cardinality and present a considerably close Multiple-Access (MA) performance to the performance of the optimum OOC codes, i.e., OOC with aut- and cross-correlation value bounded by one (or OOC lambda = 1). The large cardinality of FTH patterns completely removes the number of users constraint in OOC lambda = 1.

Moreover, these codes offer much higher security against eavesdropping and have a more uniform power in time. Another advantage of these codes is the availability of different data transmission rates for different users of the optical network. We compare the MA performance of FTH patterns to the performance of the optimum codes considering photo-detector shot noise. For this purpose, we consider a few well-known and two newly proposed receiver structures. Numerical results show that the MA performance of FTH patterns is considerably close to the performance of OOC lambda = 1 codes. The results also show that the proposed receivers have a considerable performance compared to the current practical receiver structures.