Frame time-hopping fiber-optic code-division multiple access using generalized optical orthogonal codes

In this paper, a new spreading technique for intensity modulation direct detection fiber-optic code-division multiple-access (FO-CDMA) communication systems is proposed. This new spreading technique is based on generalized optical orthogonal codes (OOC) with large cardinality and minimal degradation in performance when compared with a more optimum system, namely, an optical CDMA system using OOC with autocorrelation and cross-correlation value bounded by one, i.e., OOC (A = 1). To obtain the performance of such systems, we use a recently introduced communication scheme, namely, frame time-hopping (FTH)-CDMA with random coding. It is discussed that systems with generalized OOC patterns and random time-hopping coding are close in structure and performance. Furthermore, the performance of such systems is near the performance of optical CDMA with optimum but low cardinality OOC (A = 1), which further renders the practicality of the proposed technique with very large cardinality. Two new receiver structures for FO-CDMA, namely, chip-level detector with optimum comparator threshold and correlation receiver with an electrical hard limiter, are also proposed. Performance analysis for a binary pulse position FTH-FO-CDMA network is considered for the correlation receiver, chip-level detector, correlation receiver with an optical hard limiter, optimum receiver, and the two newly proposed receiver structures. The results also show that a chip-level detector with optimum comparator threshold is superior to a chip-level detector for received low signal powers, and predict that the performance of the correlation receiver with an electrical hard limiter is superior to all other considered receiver structures, e.g., requiring one third of transmission power to achieve a desired bit error rate when compared with other receiver structures.