In this paper, we have formulated a strategy that the limited available code sequences in pure Direct-Sequence (DS) or Frequency-Hopping (FH) system can be reused to realize dense optical CDMA: the strategy of novel hybrid DS/FH system. In which, the case that there are n users employing the same FH pattern but different DS code patterns is considered. On the condition that the impact of channel noises is neglected, the upper bound probability of error is evaluated based on the stationary random process theory. The results show that the hybrid system is suitable for Dense Optical CDMA (DOCDMA) communication. Moreover, the problems such as the link-impairment, dispersion of group velocity, etc. in the pure (DS or FH) system can be solved effectively. In this paper, we have formulated a strategy that the limited available code sequences in pure Direct-Sequence (DS) or Frequency-Hopping (FH) system can be reused to realize dense optical CDMA: the strategy of novel hybrid DS / FH system. The case that there are n users employing the same FH pattern but different DS code patterns is considered. On the condition that the impact of channel of noise noises is neglected, the upper bound probability of error is evaluated based on the stationary random process theory . The results show that the hybrid system is suitable for Dense Optical CDMA (DOCDMA) communication. Moreover, the problem such as the link-impairment, dispersion of group velocity, etc. in the pure (DS or FH) system can be solved effectively .