Fig. 1. Schematic of fast physical random number generation with retaining multiple least significant bits. EDFA, erbium-doped fiber amplifier; OBPF, optical band-pass filter; PD, photodetector; ADC, analog-to-digital converter; LSB, least significant bit.

Fig. 2. (a) The output power and applied voltage versus the injection current. Inset in (a), schematic diagram of the 2D circular-sided square microcavity. (b) The optical spectrum, (c) the RF spectra, (d) the time series, (e) the intensity distribution of the time series, and (f) the autocorrelation function of the time signal for the chaos state at 32 mA. Inset in (f), overall ACF curve within 1 µs.

Fig. 3. Probability distribution histogram of the digitalized chaotic signal with (a) LSBs = 7, (b) LSBs = 6, (c) LSBs = 5, and (d) LSBs = 4.

Fig. 4. RF spectrum of the recovered time series with retaining 4-LSBs.

Fig. 5. (a) Statistical bias and (b) absolute autocorrelation function versus the sample size of the generated 400 Gb/s random bit stream. The first 100 points of the 200-Mbits autocorrelation coefficient are shown in (b).