Physical random number, which is non-reproducible and non-periodical, has attracted much attention due to its potential applications in various fields such as secure communication, statistical analysis, and numerical simulation. Recently, fast physical random number generators based on optical chaotic entropy sources have been demonstrated to reach a rate of up to several hundreds of Gbit/s. Although many efforts have been made to optimize the schemeis of chaotic-based random number generation, most of them are based on distributed feedback semiconductor lasers and can only generate single-channel physical random number. After taking into account the costs and technological applications, the multi-channel physical random number generation technique needs developing. On the other hand, vertical-cavity surface-emitting lasers(VCSELs)can simultaneously emit two orthogonally polarized components under appropriate parameter conditions, and then each polarized component can be used as an entropy source for generating random number. As a result, VCSEL-based chaotic entropy sources may be suitable for multi-channel random number generation. In this work,a scheme for achieving multi-channel physical random number is proposed. Also the influence of the coupling parameters on the performance of the randomness of final bit sequences is investigated. For such a scheme,two orthogonally mutually coupled VCSELs are used to supply four-channel chaotic signals with a comparable output power and weak time-delay signature (TDS). The four-channel chaotic signals, which serve as chaotic entropy, are quantized by 8-bit analog-to-digital converters(ADCs)with 20 GHz sampling rate,and then the m least significant bit (m-LSB) post-processing method is adopted for generating final four-channel random bit sequences. Firstly, based on the spin-flip mode of VCSELs, the influences of coupling strength and frequency detuning on the dynamics of two orthogonally mutually coupled 1550 nm VCSELs are analyzed. Next, the optimized parameter regions for generating four-channel chaotic signals with comparable output power and weak TDS are preliminarily determined. For a given optimized value of coupling strength and different frequency detunings within the optimized parameter regions, the generated four-channel chaotic signals are taken as the entropy sources for obtaining final bit sequence by quantizing the 8-bit ADC and m-LSB post-processing. Finally, the randomness of the four final bit sequences is tested by NIST SP 800-22 statistical test suite,and the regions of preferred coupling parameters for simultaneously generating four-channel random numbers are determined.%提出将正交互耦1550 nm垂直腔面发射激光器(1550 nm-VCSEL)在优化条件下输出的多路平均功率可比拟、延时特征(TDS)得到有效抑制的混沌信号作为混沌熵源,经8位模数转换器(ADC)量化和最低有效位(m-LSB)后续处理获取多路物理随机数的方案,并研究了系统参量对最终获取的比特序列随机性的影响.首先,基于VCSEL的自旋反转模型分析耦合强度和频率失谐对两个正交互耦合1550 nm-VCSEL输出动力学的影响,初步确定利用该系统产生四路平均功率可比拟、TDS得到抑制的混沌信号所需的耦合强度和频率失谐优化范围;在此基础上,选择一个耦合强度值,利用处于优化范围内的不同频率失谐下获取的四路混沌信号作为熵源,经8位ADC量化和m-LSB后续处理得到最终的比特序列;最后,采用NIST Special Publication 800-22统计测试套件对获取的最终比特序列的随机性能进行测试,确定了同时获取四路高质量随机数所需的参数范围.
展开▼
