Novel multi-code pulse position modulation for performance improvement of 2-D OCDMA systems

In OCDMA systems, pulse position modulation (PPM) and multi-code modulation (MCM) have been proven as efficient methods for respectively mitigating multiple access interference (MAI) and dispersion. In this paper, we propose to combine PPM and MCM to create a novel modulation scheme, multi-code pulse position modulation (MCPPM). We then theoretically analyze the performance of the 2-D OCDMA system using MCPPM over a linear dispersive channel, while taking into account the negative impact of MAI, optical-beating interference (OBI), and receiver noise. It is seen that the use of MCPPM can simultaneously relax the effects of MAI, OBI, and dispersion. As a result, in comparison to the conventional systems using PPM and MCM, the one using MCPPM can support a higher user bit rate and a larger number of users. Also, a lower transmitted power can be achieved.