利用光反馈半导体激光器产生的混沌激光作为随机数熵源,详细研究了混沌源外腔长度对500Mbit/s随机数特性的影响.研究表明:在单路混沌源情况下,外腔反馈引起的谐振会使产生的随机序列具有弱周期性,且当外腔反馈时间与采样时间的比值为整数时,产生序列的随机性最差,仅能通过NIST统计测试2,3项;在两路混沌源情况下,当混沌源的外腔长不相等且不成比例时,通过两路异或处理可消除由外腔反馈引起的弱周期性,产生的随机序列能够通过NIST的全部统计测试项. Using the chaotic laser generated by the optical feedback semiconductor laser as the random number entropy source, the influence of chaotic source external cavity length on the random number characteristics of 500 Mbit / s is studied in detail.The results show that the resonance induced by external cavity feedback The random sequence generated will have weak periodicity. When the ratio of external feedback time to sampling time is an integer, the randomness of the generated sequence is the worst, which can only pass the NIST statistical test of 2 and 3 items. In the two chaotic sources In the case where chaotic source external cavities are unequal and disproportionate, the weak periodicity caused by external cavity feedback can be eliminated by two exclusive ORs and the resulting random sequence can pass all the NIST statistical test items.