Impact and Mitigation of Noise in Optical 2D Techniques Using (n, w, λa, λc) Optical Orthogonal Codes for Optical CDMA

Abstract

The performance of two dimensional (2D) hybrid wavelength/time optical code division multiple access (OCDMA) system is affected severely by the presence of noise at its physical layer. This noise is present in the guise of multiple access interference (MAI) and beat noise in OCDMA systems and degrades its performance. In this paper an attempt has been made to analyze the impact of noise in OCDMA system using four different coding schemes. The mitigation of noise is then done by using either optical hard limiter (OHL) or by utilizing coherent detection for all these schemes. These codes use synchronized quadratic congruence sequences (SQC), synchronized prime procession (SPP), prime code sequences (PC) and synchronized prime sequences (SPS) for wavelength hopping and (n, w, λ_a, λ_c) one dimensional optical orthogonal codes for time spreading respectively. The code with heavier code weight or lower values of auto- and cross- correlation function performs the best with noise mitigation techniques. Investigations reveal that SQC/OOC coding scheme in combination with OHL and PC/OOC scheme in combination with coherent detection outperforms in comparison to other techniques.