| Random numbers are widely used in the fields of radar,remote sensing measurement,confidential communication,cryptography,etc.Random numbers are usually used as radar signal,remote sensing measurement signal,group synchronization and encryption decryption in digital communication,the address code and spreading code in CDMA,and the key in cryptography.With the development of modern technology,random numbers have also used in the fields of aerospace,automatic control,driverless and information security.Traditional pseudo-random numbers generated by complex algorithms are hidden dangers in the application process of many fields due to the essence of its certainty,and random numbers generated by physical entropy sources have attracted additional attention.How to obtain high-quality and high-speed random numbers from physical entropy sources has gradually become a research hotspot,and multiple plans have been proposed one after another.Among them,chaotic signal from a semiconductor laser under optical feedback as physical entropy source to obtain random numbers has attracted much attention since the first realization in 2008.In this scheme,how to obtain high-quality chaotic signal based on a semiconductor laser under optical feedback,and efficient post-processing method are two key technologies.This thesis has carried out the following works around these two key technologies:1.For the obvious time-delayed-signature(TDS)in chaotic signal generated by a semiconductor laser under single optical feedback,this thesis proposes a semiconductor laser under multi-path optical feedback to generate low TDS chaotic signal.The theoretical simulation and experimental results show that compared to a semiconductor laser under single optical feedback,under the same system conditions,the chaotic signal generated by a semiconductor laser under multi-path optical feedback has lower TDS,and the feedback intensity of a semiconductor laser under multi-path optical feedback which is linked to weak TDS(TDS peak less than 0.1)has a wider range.In-depth research on the performance of a semiconductor laser under multi-path optical feedback with different fiber couplers discovered that the TDS of the chaotic signal generated by a semiconductor laser under multi-path optical feedback with different fiber couplers has a great different,and the length of the feedback circuit has a weak influence on the TDS of the chaotic signal.2.Although the chaotic signal generated by a semiconductor laser under multi-path optical feedback presents a low TDS under the appropriate system parameters,its bandwidth is relatively small(its bandwidth is limited to the relaxation of the laser,only a few GHz),which is used as physical entropy source is difficult to produce high-speed random numbers.In order to settle this problem,the chaotic signal with low TDS is injected into another laser to increase the chaotic bandwidth.The theoretical simulation and experimental results show that by selecting system parameters such as the appropriate injection intensity and frequency detuning,the bandwidth of the chaotic signal can be significantly enhanced by use this new method.In particular,with the help of light injection,the TDS of the chaotic signal can be further weakened.A chaotic signal with effective bandwidth of 26 GHz and TDS peaks less than 0.02 is obtained in the experiment.3.The low TDS and large bandwidth chaotic signal obtained by the above experiment is used as entropy source and with the help of high-speed sampling and circulating exclusive-or post-processing method,random numbers with a rate of 640Gb/s it obtained.The high-quality chaotic signal is first sampled by an analog-to-digital converter with 8-bit vertical resolution and 80 GSa/s sampling rate.Then,the sampling data is carried out by circulating exclusive-or post-processing method,and random numbers with a rate of 640 Gb/s is obtained.Tested the generated sequence by statistical histogram,two-dimensional dot diagram,the National Institute of Standard Technology Special Publication 800-22 statistical tests(NIST statistical test suite),and triple standard deviation tests,and the results show that the generated sequence can pass all the tests.In addition,probability calculation indicates that circulating exclusive-or post-processing method can greatly improve the balance of sequence distribution.Because there is no need to abandon any sampling points,almost all sampled bits are used,and all the information of the entropy source is retained,so the random numbers with max rate can be achieved under the condition of the given vertical resolution and sampling rate.4.On the basis of the above work,the two sampling sequences are combined into a sequence through the sampling points interleaved combination.Using the combined sequence combined with circulating exclusive-or post-processing method to further increase the generating rate of random numbers.Based on the above research,two independent sets of chaotic light injection system based on a semiconductor laser under multi-path optical feedback are used to generate two low TDS and large bandwidth chaotic entropy sources.Then two sampled sequences are obtained by two analog-to-digital converters with 8-bit vertical resolution and 80 GSa/s sampling rate.Next,the two sampling sequences are combined into a sequence through the sampling points interleaved combination,and circulating exclusive-or post-processing method is performed.In the end,random numbers which passed the NIST statistical test suite was obtained and its rate is as much as 1.28 Tb/s.Because the process of this scheme is relatively simple,it is easy to use this scheme to more independent and stable chaotic entropy sources,so it has the potential to further increase the rate of random numbers generation. |
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