Optical Sampling Of Chaotic Laser Using Terahertz Asymmetric Demultiplexer

Random number is now widely used in the field of information security, spread spectrum communication, radar test, cable and fiber breakpoint detection and so on. The quality of random number is especially important in the field of information security based on cryptography. Random number can be divided into two categories, one is pseudo random number and the other is physical random number. Pseudo random number is generated by means of seeds and algorithm, although the rate is high, there will be a certain periodicity sometimes. In addition, it is easy to be cracked. While physical random number is generated by means of random physical phenomena, such as electronic thermal noise, amplified spontaneous emission noise (ASE), oscillator frequency vibration, chaotic laser and so on. Because the chaotic laser has the characteristics of high bandwidth and weak correlation, it has been conducted by a lot of research groups to generate random number. We can obtain hundreds of Gbit/s physical true random number from the chaotic laser, through analog-to-digital conversion and subsequent series-parallel conversion. However, these processes cannot complete without the optical to electric conversion, so the rate of random number generated by the direct implementation of electronic is limited to only a few G bit/s by bottleneck. So our group proposed a scheme to generate random numbers in all-optical domain, so that there will not be the electronic bandwidth limitations, thus greatly improve the rate of random number. To achieve all-optical random number, both chaotic laser sampling and quantization in optical domain is needed. This paper is mainly about the study of sampling of chaotic laser in the optical domain.The mainly work can be included as follows:1. Firstly, we introduce the classification and the development of random number at present, compare the advantages and disadvantages of the existing random number generator, and explain the necessity of all-optical random number generator. Then we introduce the scheme of all-optical random number generator that our research group proposed, and show a brief introduction to the project. According to the characteristics of chaos, such as weak coherent strength, the random variation of polarization state, we analyze the feasibility of all-optical sampling of chaotic laser. 2. According to the characteristics of chaotic laser, such as poor coherence random fluctuation of polarization, we propose the use of terahertz asymmetric demultiplexer (TOAD) to realize the sampling scheme of chaotic laser. The key device in this scheme is the semiconductor optical amplifier (SOA), so we pay attention to the internal physical processes and some nonlinear effects of the nonlinear device SOA.3. Based on the effect of cross phase modulation in SOA, we realize the sampling of chaotic laser using TOAD, and analyze the effect of the peak power, full width at half maximum of the pump pulse, and the offset of SOA and other parameters on the sampling results. We evaluate the sampling results according to two indexes, one is the final output of power and the other is the sampling linearity R2. Taking these two factors into account, we obtain the best sampling condition for chaotic light, realizing the optimal sampling of1.25GHz. The simulation provides theoretical basis for the realization of chaotic laser sampling in the experiment using TOAD.4. Summarize the contents in this paper and put forward prospects for the future.