Threshold-based vs. demodulator-based code acquisition for PPM/OPPM FO-CDMA systems

This paper proposes and theoretically evaluates two different schemes of code acquisition for pulse-position modulation (PPM), overlapping PPM (OPPM) fiber-optic code-division multiple-access (FO-CDMA) systems, namely threshold-based and demodulator-based code acquisition. The serial-search algorithm is employed for both schemes. Theoretical analysis is carried out with help of a Markov chain model. Discussions upon effects of various parameter settings on the performance of code acquisition for PPM/OPPM FO-CDMA systems, such as index of overlap, PPM/OPPM multiplicity factor, average photon counts per information nat, and darkcurrents, are presented.