On the Code Synchronization of PPM/OPPM Fiber-Optic CDMA Systems

Hiroyuki YASHIMA

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E87-A    No.10    pp.2692-2701
Publication Date: 2004/10/01
Online ISSN: 
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Wide Band Systems)
fiber-optic CDMA,  PPM,  OPPM,  optical orthogonal codes,  code acquisition and synchronization,  serial-search algorithm,  multiple-access interference,  shot-noise-limited receiver,  

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This paper proposes and theoretically evaluates two different schemes of code acquisition for pulse-position modulation (PPM) and overlapping PPM (OPPM) fiber-optic code-division multiple-access (CDMA) systems, namely threshold-based and demodulator-based code acquisition. Single-dwell detector and serial-search algorithm are employed for both schemes. Theoretical analysis is carried out for shot-noise-limited photon-counting receiver. Discussions upon effects of various parameter settings on the performance of code acquisition for PPM/OPPM fiber-optic CDMA systems, such as index of overlap, PPM/OPPM multiplicity, average photon counts per information nat, and darkcurrents, are presented. It is shown that when the threshold is properly selected, the threshold-based code acquisition system offers better performance, in terms of mean number of training frames, than the demodulator-based one.