Optical chaos bandwidth broadening by nonlinear propagation for random bit generation

Abstract

Optical chaos has been widely used in secure communications and cryptography, high-resolution chaotic lidar, and Monte Carlo simulations, where large bandwidth is crucial. For secure communications applications and Monte Carlo simulations, randomness is extracted from chaos in the form of random bits. Semiconductor lasers under optical injection can emit chaotic light. Optical fibers have intrinsic optical nonlinearity that can broaden the chaotic bandwidth as chaotic light propagates along optical fibers. In this project, chaos with bandwidth of 13.1 GHz generated by an optically injected semiconductor laser propagates along a 5-km single-mode fiber with 1-W input power, producing bandwidth-enhanced chaos with bandwidth of 119 GHz. A 1-bit analog-to-digital converter (ADC) and a 2-bit digital counter is then used to extract random bits at a rate of 20 Gbps from the bandwidth-enhanced chaos. Since a 1-bit ADC and a digital counter is utilized to replace a widely used 8-bit ADC for random bit generation, the hardware requirement is alleviated. The above physical random bit generator is demonstrated through simulation. Since the maximum extractable random bit rate is proportional to the bandwidth of entropy source, broad-bandwidth chaos has the potential for ultra-fast random bit generation with bit rate up to a few Tbps.