PERFORMANCE ANALYSIS OF DIRECT-DETECTION OPTICAL CDMA COMMUNICATION-SYSTEMS WITH AVALANCHE PHOTODIODES

Direct-detection optical code-division multiple-access (CDMA) communication systems with avalanche photodiode (APD) photodetectors are investigated. A Chernoff upper bound, modified Chernoff upper bound, and Gaussian approximation on the probability of bit error (pbe) are presented for general APD's and arbitrary {0, 1}-valued optical signature sequences. Multiple-user interference, shot-noise, and receiver thermal noise effects on the pbe are studied in detail. One-coincidence optical orthogonal codes and prime codes are considered in the numerical analysis. Equal-weight orthogonal signaling formats that do not require dynamic estimation of the receiver threshold are proposed. Our results suggest that equal-weight orthogonal signaling schemes are preferable to the on-off orthogonal signaling schemes commonly employed in the literature.