Time-delay signature characteristics of the chaotic output from an optoelectronic oscillator by introducing an optical feedback

In this work,via autocorrelation function(ACF)and permutation entropy(PE)methods,we numerically investigate the time-delay signature(TDS)characteristics of the chaotic signal output from an optoelectronic oscillator(OEO)after introducing an extra optical feedback loop.The results demonstrate that,for such a chaotic system,both the optoelectronic feedback with a delay time of T1 and the optical feedback with a delay time of T2 contribute to the TDS of generated chaos.The TDS of the chaotic signal should be evaluated within a large time window including T1 and T2 by the strongest peak in the ACF curve of the chaotic signal,and the strongest peak may locate at near T1 or T2.Through mapping the evolution of the TDS in the parameter space of the optical feedback strength and time,certain optimized parameter regions for achieving a chaotic signal with a relatively weak TDS can be determined.

Massive and parallel 10 Tbit/s physical random bit generation with chaotic microcomb

Ultrafast physical random bit(PRB)generators and integrated schemes have proven to be valuable in a broad range of scientifc and technological applications.In this study,we experimentally demonstrated a PRB scheme with a chaotic microcomb using a chip-scale integrated resonator.A microcomb contained hundreds of chaotic channels,and each comb tooth functioned as an entropy source for the PRB.First,a 12 Gbits/s PRB signal was obtained for each tooth channel with proper post-processing and passed the NIST Special Publication 800-22 statistical tests.The chaotic microcomb covered a wavelength range from 1430 to 1675 nm with a free spectral range(FSR)of 100 GHz.Consequently,the combined random bit sequence could achieve an ultra-high rate of about 4 Tbits/s(12 Gbits/s×294=3.528 Tbits/s),with 294 teeth in the experimental microcomb.Additionally,denser microcombs were experimentally realized using an integrated resonator with 33.6 GHz FSR.A total of 805 chaotic comb teeth were observed and covered the wavelength range from 1430 to 1670 nm.In each tooth channel,12 Gbits/s random sequences was generated,which passed the NIST test.Consequently,the total rate of the PRB was approximately 10 Tbits/s(12 Gbits/s×805=9.66 Tbits/s).These results could ofer potential chip solutions of Pbits/s PRB with the features of low cost and a high degree of parallelism.