Third Communication Theory Mini-Conference in conjunction with Globecom '94 PHASE DRIFT EFFECTS IN OPTICAL CDMA

Fiber optic communication systems using CDMA have been proposed. While coherent detection is a reasonable assumption in many RF systems , semiconductor lasers for ber applications have been shown to suuer from more serious phase variation that precludes fully coherent detection, the focus of previous CDMA research. In this paper we examine the eeect of phase drift on several multiuser detectors for BPSK, as well as two detectors for BFSK. We show that when the desired user's phase can be tracked, BPSK match ltering ooers better bit error rates than BFSK, and we derive closed form solutions for the error probabilities in the limit of innnitely long spreading codes modeled as a random sequence of plus and minus ones. When there is no phase tracking, we show that the probability of error of the multiuser detectors approaches one half.