Optical CDMA system using optical hard-limiter and 2-D RLL code

In this paper, we employ optical hard-limiter and 2-D RLL code to alleviate the adverse impact of MAI and beat noise in time-spreading wavelength-hopping optical CDMA system. Based on the spatial coding, the 2-D RLL code can enlarge the free distance in a trellis code, thus can enhance the system performance. In addition, the utilization of optical hard-limiter can not only further reduce the interference which comes from other interferers but also completely eliminate the beat noise. Apart from the beat noise, some of the negative effects of noises are taken into account, which include thermal noise, shot noise, and relative intensity noise. The numerical results show that the proposed scheme can improve system performance significantly.