Construction of Optimal 2D Optical Codes Using (n,w,2,2) Optical Orthogonal Codes

Two-dimensional (2D) wavelength-time coding schemes have recently been studied for optical code-division multiple access. In this paper, we propose a new family of 2D codes, which use "synchronized" quadratic congruence sequences for wavelength hopping and (n, w, 2, 2) optical orthogonal codes for time spreading. The new 2D codes provide larger (asymptotically optimal) code cardinality than other 2D codes by relaxing the maximum cross-correlation function from one to two. Our study shows that the heavier code weight supported by our 2D codes results in better code performance than some of previously proposed 2D codes (of the maximum cross-correlation functions of one and two). The new codes potentially support more subscribers and heavier bursty asynchronous traffic with gradual performance degradation as traffic load increases.