All-optical Random Number Generation Based On The Nonlinear Effects In Highly Nonlinear Fiber

Random numbers have a wide range of applications in information security, scientific computing, commercial finance and other fields. Especially in the field of information security which is based on the cryptography, the quality of random number is directly related with the secure transmission of information. Random numbers can be divided into pseudo-random number and physical random number according to the different producing methods. Pseudo-random number is generated by seed which should be processed by deterministic algorithm. The physical random is achieved through processing the physical source of natural world applying the electronic device, such as resistor thermal noise, the oscillator frequency jitter, the photon noise, amplified spontaneous emission noise, chaotic laser etc. Among them, the chaotic laser is the most attractive entropy source for high-speed true random number generation in recent years, due to its highly sensitive to initial conditions, high bandwidth and other factors. 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, the subsequent operations are using software processing. The way of single way is still limited by the bottleneck of electronic devices. Moreover, in the face of the rapid development of all-optical communication network, the electric random number generators need optical-electric-optical converters, which seriously affect information processing speed and the cost of project. In order to overcome the electronic bottleneck problem, our experimental groups proposed a series of schemes of all-optical random number generator which can better compatible with high-speed optical communication network. In these schemes, we can achieve10Gbit/s random number by use of1-bit analog-to-digital conversion,The main contents are summarized as follows:1.Firstly, we introduce the application and the research progress of random number generator, analyze in detail the advantages and disadvantages of the random number generator and indicate the significance to research the all-optical random number. Secondly, we mainly introduce the schemes of all-optical random number which were proposed by our experimental group in recent years. Lastly, we sum up current all-optical sampling technology, and analyze the feasibility of all-optical sampling to chaotic laser.2. Based on four-wave mixing in highly nonlinear fiber, a scheme to chaotic laser sampling independent of polarization is proposed due to poor coherence of chaotic laser, and random fluctuations of polarization state. Combining with characteristics of chaotic laser and four-wave mixing phase matching conditions, the parameters of pump laser is determined, such as light wavelength, power, repetition rate, fiber length, which can make the four-wave mixing sampling efficiency be optimal. Polarization insensitive sampling for chaotic laser which wavelength is1550nm and power range is0-10mw, is implemented with sample rate of5GHz by numerical method. The results can provide a theoretical basis for the further experiment.3. Based on the nonlinear effects in highly nonlinear fiber, a new scheme of all-optical random number is proposed. In the program, utilizing ultra-wideband chaotic laser as entropy source, we generate10Gbit/s random numbers through the all-optical sampling, all-optical comparator and all-optical exclusive-or (XOR) operations, which are realized by four-wave mixing and cross-phase modulation in highly nonlinear fiber. Lastly, the random numbers pass through the NIST standard statistical test. The entire operations are completed in the all-optical domain, which can overcome the bottleneck problem of electronic devices, and compatible high-speed all-optical communication network.4. Summary and outlook for future research.