Reducing the Dispersion Effects in Multiwavelength Optical CDMA Systems by Using MCM Signaling

We propose a novel multiwavelength optical code-division multiple-access (OCDMA) system using multicode modulation (MCM) signaling. For the multicode demodulator, we employ a maximum-likelihood detection and optical hard limiters. The work in this paper theoretically analyzes the performance of the proposed system over linear dispersive channels, while taking into account the impacts of multiple-access interference (MAI), optical-beating interference (OBI), and receiver noise. It is seen that the use of MCM can significantly relax the effects of chromatic dispersion. In addition, MAI and OBI can be effectively mitigated in the proposed system. As a result, in comparison with the conventional systems using on-off keying (OOK) modulation and pulse-position modulation (PPM), the proposed system can support a higher user bit rate and a larger number of users. Also, a lower transmitted power is required and a longer transmission length can be achieved.