RIA: All-Optical Code Division Multiple-Access Communication Systems

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9409452 Brandt-Pearce An optical free-space or fiber communications network can theoretically support several terabits per second total information throughput. Several possibilities of design of multi-user optical systems are proposed such that the bandwidth is utilized efficiently. Code-division multiple-access (CDMA) has been chosen as the multiplexing scheme due to its flexibility and efficiency. The thrust of this research is the design and subsequent analysis of all-optical modulation and demodulation techniques for coherent detection and incoherent detection optical CDMA. A symbol detector must be implemented optically if the overall CDMA spreading gain and user data-rate is to remain unrestricted. The conventional optical CDMA system suffers a through-put limit orders of magnitude lower than the theoretical limit due to its poor symbol detection algorithm (the correlation detector). First, several alternative detection algorithms relying on all-optical processing for an incoherent (direct-detection) system are proposed that improve the throughput and performance without imposing an excessive hardware complexity. Then several multi-user detection algorithms are proposed for a coherent (heterodyne) detection optical system. Optical processing is used on the broadband CDMA signal, followed by an electronic symbol decision algorithm. The bit-error probability is approximated by using large deviations theory, moment space bounds, and importance sampling simulations. ***