All-optical Random Number Generator

Random number generators have a wide range of applications and play a crucial role in nation's science, technology and information security strategy. With the development of modern computation and communication technology, high data rates require high speed random number generators with good quality.There are two types of random number generators which can generate random bits or numbers. Deterministic algorithms, the first type, can generate random numbers at high rates, but their quality is unfavorable due to the very nature of their deterministic origin. The core of random numbers is non-determined and unpredictable. Thus, good quality random number generator should be achieved by means of physical random processes. Unfortunately, the generation rates of traditional physical random number generators are only of the order of several Mbit/s due to the limitation of bandwidth although the randomness of the generated random numbers gets improved.Distinct with those physical sources above, chaotic lasers can generate large-amplitude, wide frequency spectrum and noise-like signals from microscopic noise by nonlinear amplification and mixing mechanisms. They are ideal candidates of physical random number generators with good quality. Until now, there have been lots of random number generators based on chaos, but all of them process their signals in the electric domain and thus their rates will be finally restricted by the bottleneck of electronic signal processing. In this paper, we make use of chaos in laser to achieve efficient generation of all-optical random numbers at high rates which can overcome the "electronic bottleneck". The main research contents are mentioned as below:1. The methods of generating random numbers and their application are generalized. The merits and drawbacks of common methods are analyzed and summarized. Especially, existing random number generators based on chaotic lasers are emphasized. It indicates that it is significant to design a kind of random number generator based on chaotic lasers which do all signal processing in the optical domain—all-optical random number generators.2. Two schemes of random number generator are proposed and demonstrated. One is comprised of three parts:an ultra-wide bandwidth (UWB) chaotic laser as random number source, a Sagnac interferometer as all-optical sampler and aλ/4-shifted DFB lasers (λ/4 DFB) as all-optical comparator. The other mainly consists of a chaotic laser, an electro-optical modulator (EOM) and an all-optical flip-flop. The generation rate of both schemes can reach several Gbit/s.3. Post processing, i.e. exclusive or (XOR), is introduced to improve quality of random number. The generated high-speed random numbers can successfully pass the standard statistical tests for randomness, i.e. the test suite of the National Institute of Standard Technology (NIST).4. In the last chapter, we sum up our works and give some advices about the future works.