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 (2-D) 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 probability of error (bit-error rate) in terms of multiuser interference and the maximum number of codes that can be generated. We show that 2-D 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(-9).