Design and performance of 2-D codes for wavelength-time optical CDMA

In this letter, we use a depth-first search algorithm to generate two-dimensional (2D) codes with unit auto- and cross-correlation properties for wavelength-time optical code-division multiple access (CDMA) systems. We examine how the code weight and size (number of wavelengths and/or time chips) affect the two important system parameters, namely the error probability (bit-error rate) in terms of multiuser interference and the maximum number of codes that can be generated. We show that 2D wavelength-time optical CDMA systems should use codes with low weight and a high wavelength to time chip ratio. The depth first search algorithm allows us to generate significantly more codes than previously proposed code construction algorithms; when used in conjunction with forward error correction, our approach potentially allows for a large number of simultaneous users operating with a BER<10/sup -9/.