5. Conclusions

We have reviewed a serial of novel data encryption schemes for physical-layer security enhancement for optical OFDM transmission. By incorporating multi-fold digital chaos-based data encryption in various DSP procedures in OFDM signal generation, modulation as well as OFDM symbol synchronization, data security is greatly enhanced with a huge key space. Moreover, the OFDM transmission performance is significantly improved because the pseudo-random properties of digital chaos are employed for effective PAPR reduction. Moreover, for the chaotic precoding schemes, the reconfigurable chaotic precoding matrices are predetermined by digital chaos; therefore, the sideband information is no longer necessary, which also improves the spectral efficiency in transmission. The proposed chaotic data encryption schemes have been successfully demonstrated by ~10 Gb/s OFDM transmission experiments, which verifies that these schemes could be promising candidates for next-generation secure OFDM-PON.
