High-Speed Random Bit Generation Based on Chaotic Laser Signals and PAM-Based Amplitude Redistribution

This work presents a novel high-speed random bit generation approach based on chaotic optical signals combined with a pseudo-random pulse amplitude modulation (PAM) sequence. Chaotic dynamics generated by a laser diode under optical feedback provide the physical entropy source. At the same time, the PAM signal is added as an amplitude-level transformation to enhance the statistical distribution of the digitized signal. Unlike conventional post-processing techniques such as least significant bit (LSB) extraction, which reduce the effective bit rate, the proposed method described in this article preserves the full 8-bit resolution of the analog-to-digital converter improving the distribution of amplitude levels. Experimental results show a significant improvement in compliance with the NIST SP 800-22 statistical test suite. The system operates at a sampling rate of 20 GSa/s, achieving a theoretical bit generation rate of 160 Gb/s. These results demonstrate that the proposed approach provides an alternative to conventional digital post-processing techniques while maintaining high throughput.