Abstract
Semiconductor laser can generate various nonlinear dynamical states by the action of optical feedback (OF) system including periodic-one oscillation state (P1), quasi-periodic oscillation state (QP), chaotic oscillation state (C) and so on. Through the calculation of autocorrelation of time series in chaotic oscillation state, we can find the time delay signature (TDS). This phenomenon is unfavorable to apply in random number generator~(RNG) because of it's special periodicity. In this study, TDS is suppressed and random number is generated by different interference techniques. First, we use the Delayed Self-Interference (DSI) to be the basic standard of comparison of the whole study. The setup of the DSI combined the OF system and Mach–Zehnder interferometer (MZI). With a proper power and feedback strength, the TDS reduction ratio can be up to 35%. Then we add a acousto-optic modulator (AOM) to improve the DSI, which called the Delayed Self-Heterodyne Interference (DSHI). Through the design of the external cavity length and the frequency of the AOM, the TDS reduction ratio can be up to 65%. We change the MZI setup to the Loss-Compensated Recirculating Delayed Self-Heterodyne Interferometer (LC-RDSHI). The LC-RDSHI chaos signal is equal to a multiple-beam interference results, which can suppress the TDS value more. We calculate the TDS reduction ratio of 92%. In addition, the effective bandwidth enhancement ratio can be up to 52%. On the other hand, we demonstrate the different interference techniques for generation of random number. The NIST Special Publication 800-22 Statistical Tests evaluated the randomness of chaos signal. The bit sequences of the LC-RDSHI signal can generate higher bit rate from 10 to 50 Gigabit per second than the DSI and the DSHI. The high random bit generation rates can be used to confidential communication and military application.