Dual-channel Physical Random Bits Generation By A Master-slave Vertical-cavity Surface-emitting Lasers Chaotic System

Physical random bits(PRB)are widely used in the fields of computing and secure communications due to the advantages of non-periodicity,non-predictability,and nonreproducibility.The entropy source of traditional PRB generators are based on amplified thermal noise of the resistor,metastability of circuit and frequency jitter of oscillators.However,the bandwidth restricts the rate of generating random bits with the order of Mbit/s,and then there is a large gap between the generation rate and the transmission rates of current optical communication systems.Wide-bandwidth chaotic signals can be obtained from semiconductor laser under the external disturbances such as optical injection,optical feedback and photoelectric feedback.High-speed random bits can be obtained based on the chaotic signal as entropy source.The high-speed physical random bits generation based on the chaotic time series of wide-bandwidth semiconductor lasers has been widely studied by scholars,and one of the key technology is to obtain highquality chaotic signals with good randomness,large spectral bandwidth and weak periodicity.Up to now,most researches are based on the single-channel random bit generated by distributed feedback semiconductor lasers(DFB-SLs).Compared with DFB-SLs,vertical-cavity surface-emitting lasers(VCSELs)possess some unique virtues such as small size,low threshold,single-longitudinal-mode output,and easiness to photonic integration.Especially,VCSELs can simultaneouly lase at two orthogonally polarization components under appropriate parameter conditions,which theoretically can be used as chaotic entropy sources to generate dual-channel PRBs.Double-channel random bit can be directly used in the fields of multi-channel communication security.Besides,a random bit with double rate can be obtained via cross-merging operation.In this paper,we propose a scheme for acquiring dual-channel high-speed physical random bits(PRBs)by taking the chaotic output from a master-slave framework chaotic system as chaotic entropy resource.For such a scheme,a vertical-cavity surface-emitting laser(VCSEL)under polarization-preserved optical feedback from a fiber Bragg grating(FBG)is utilized as the master VCSEL(M-VCSEL).Under suitable operating parameters,both X and Y polarization components(X-PC and Y-PC)of the M-VCSEL can output chaotic signals with comparable power and weak time-delay signatures(TDS).The chaotic outputs from the X-PC and Y-PC of the M-VCSEL are divided into two parts,and then injected into the corresponding polarized component of another VCSEL(named as slave VCSEL,S-VCSEL)after undergoing different flight-time,and such an injection method is named as dual-path polarization-preserved optical injection(DP-PPOI).The X-PC and Y-PC in the S-VCSEL under DP-PPOI can simultaneously output chaotic signals with enhanced bandwidth,which are quantified by 8-bit analog-to-digital converters(ADC)and taken as the entropy sources for generating dual-channel bit sequence after adopting m least significant bits(m-LSBs)extraction and logical exclusive-OR(XOR)post-processing.Finally,the randomness of the bit sequences generated under optimized parameters is tested by NIST SP 800-22 statistical test suite.The results demonstrate that dual-channel random bits at rate of 500 Gbit/s can be obtained,and the rate of random bits can be further increased to 1 Tbit/s through adopting cross-merging method.