Comparison of BER performance limits for coherent ultrashort light pulse and incoherent broadband CDMA systems

Abstract

Summary form only given. Recently, there has been considerable research activity on optical code-division multiple access (CDMA) for local area network applications with systems based on coherent processing (manipulation of optical fields) holding the most promise. Coherent processing may be achieved using either incoherent (e.g., amplified spontaneous emission) or coherent (modelocked pulse) broadband optical sources, together with appropriate receiver structures. CDMA approaches using incoherent sources, such as coherence multiplexing and spectral amplitude coding, called incoherent broadband CDMA (INC-CDMA) offer the advantage of simpler technology. However, recent analyses have shown that INC-CDMA approaches are limited to throughputs of /spl sim/10-25 Gb/s. On the other hand, an analysis of ultrashort CDMA (US-CDMA) using spectral phase coding of coherent ultrashort pulses predicted that throughput could in principle exceed 100 Gb/s, although realization of the full potential of this scheme requires advanced femtosecond technology and is still a research challenge. We perform the first comparison of the theoretical bit-error-rate (BER) and throughput performance of INC-CDMA and US-CDMA for a common set of system parameters and explain the difference in predicted performance.