Experimental investigation of the time-delay signature of chaotic output and dual-channel physical random bit generation in 1550 nm mutually coupled VCSELs with common FBG filtered feedback

Here we propose and experimentally demonstrate mutually coupled 1550 nm vertical-cavity surface-emitting lasers (VCSELs), subject to common fiber Bragg grating (FBG) feedback (FMC-VCSELs), to conceal the time-delay signature (TDS) of chaotic outputs. The autocorrelation function and delayed mutual information are used to quantitatively identify the TDS of chaotic output. For comparison, the evolution of the TDS of chaotic output in mutually coupled VCSELs (MC-VCSELs) is also presented. The effects of injection power, frequency detuning between two VCSELs, and frequency detuning between FBG and VCSELs on the TDS concealment are experimentally measured. Experimental results show that FMC-VCSELs have a better TDS suppression performance than MC-VCSELs for varying injection power. In addition, for the FMC-VCSELs system, the TDS can be suppressed to below 0.1 when the VCSELs x-polarization component is located at the edge of the main FBG lobe. Furthermore, dual-channel physical random numbers with verified randomness at a rate of 800 Gbps (2×5LSBs×80GHz) are achieved by utilizing the chaotic outputs with a low TDS from two VCSELs in the FMC-VCSELs system.