Employment of 2-D RLL precoder and optical hard-limiter in optical CDMA system

In this paper, the 2-D RLL Precoder and optical hard-limiter are utilized in time-spreading wavelength-hopping optical CDMA system, which the system performance can be drastically enhanced. In optical CDMA system, the error floor effect occurs due to the adverse impact of MAI and beat noise; this will severely limit the system performance. Employing optical hard-limiter can effectively to eliminate the detrimental effect of MAI and beat noise, thus further reduce the error floor. In addition, we also utilize spatial coding scheme to construct a 2-D RLL precoding mechanism, which the free distance is larger than 1-D RLL trellis. Aside from the beat noise, some of the physical noises are also taken into consideration, which include thermal noise, shot noise, and relative intensity noise. The numerical results reveal that our proposed scheme can improve system performance significantly.