2/sup n/ codes for optical CDMA and associated networks

Optical coders and decoders that avoid the high excess losses experienced by code-division multiaccess (CDMA) networks using prime codes are reported. A ladder structure, which is probably the most energy-efficient passive structure for such applications, is used; regardless of its length, it only introduces a power reduction by 2 for a matched decoder. The new codes corresponding to the ladder networks are named the 2/sup n/ codes, since the peak power reduction factor P=2/sup n/, where (n+1) is the number of couplers. They are quite different from the prime codes in their temporal structures: for example, only symmetric pulse patterns are allowed. A standard signal-to-noise analysis for the simplest class of possible codes (orthogonal) shows that the 2/sup n/ codes are quite comparable to the prime codes, in that comparable BERs with code sequences of approximately the same length, and similar numbers of possible codes to accommodate the users, are obtained.<>