A novel double masking scheme for enhancing security of optical chaotic communication based on two groups of mutually asynchronous VCSELs

The emergence of optical chaotic secure communication has opened up an alternative path for information security. In this paper, based on two groups of mutually asynchronous vertical-cavity surface-emitting lasers (VCSELs), a novel double masking (DM) scheme for enhancing security of optical chaotic communication is proposed. We numerically analyze the synchronization characteristic of the lasers and the suppression of the time-delay signature (TDS). The self-correlation function (SF) and permutation entropy (PE) are employed to extract the TDS. Meanwhile, based on the high quality synchronization, we also investigate the communication performances of DM scheme in a long distance. Especially, the influence of the time delay due to delay fiber (DF) on the communication quality in different cases is studied. The results show that the TDS can be suppressed by the DM scheme to some certain degree. Four messages of 10 Gbit/s can be propagated in 138 km single mode fiber (SMF) after introducing the dispersion compensating fiber (DCF), bidirectionally and simultaneously. When the BER ⩽10-9 and Q factor ⩾6, the DM scheme has smaller critical value of the time shift (Δt) than the single masking (SM) system, which indicate a good level of security.