Abstract
Chaotic external-cavity semiconductor laser (ECL) is a promising entropy source for generation of high-speed physical random bits or digital keys. The rate and randomness is unfortunately limited by laser relaxation oscillation and external-cavity resonance, and is usually improved by complicated post processing. Here, we propose using a physical broadband white chaos generated by optical heterodyning of two ECLs as entropy source to construct high-speed random bit generation (RBG) with minimal post processing. The optical heterodyne chaos not only has a white spectrum without signature of relaxation oscillation and external-cavity resonance but also has a symmetric amplitude distribution. Thus, after quantization with a multi-bit analog-digital-convertor (ADC), random bits can be obtained by extracting several least significant bits (LSBs) without any other processing. In experiments, a white chaos with a 3-dB bandwidth of 16.7 GHz is generated. Its entropy rate is estimated as 16 Gbps by single-bit quantization which means a spectrum efficiency of 96%. With quantization using an 8-bit ADC, 320-Gbps physical RBG is achieved by directly extracting 4 LSBs at 80-GHz sampling rate.
Highlights
Fast physical random bit generation (RBG), used to supply digital key, is of vital importance to information security of current high-speed optical communication [1,2,3,4]
Physical RBG based on chaotic external-cavity semiconductor lasers (ECLs) has attracted intensive attention because the generation speed can readily exceed one gigabit per second (Gbps) [5,6]
The rate of RBG can be greatly improved to hundreds of Gbps and even over Tbps by using multi-bit extraction method, in which each sampling point is converted to several digital bits by using a multi-bit analog-to-digital converter (ADC) [10,11,12,13,14,15,16,17,18,19,20]
Summary
Fast physical random bit generation (RBG), used to supply digital key, is of vital importance to information security of current high-speed optical communication [1,2,3,4]. Demonstrated by Kanter et al, first-order derivative post processing obtained 12.5-Gbps (5 LSBs retained × 2.5 GHz sampling rate) random bits from a chaotic ECL [11]; by contrast, achieving 300 Gbps (15 LSBs × 20 GHz) required 16th-order derivative [14]. For XOR processing, as reported by Uchida et al, a generation rate of 400 Gbps (8 LSBs × 50 GHz) was achieved using a bandwidth-enhanced chaos with bit-order reversal time-shift XOR [17], whereas only 75 Gbps (6 LSBs × 12.5 GHz) was obtained without bit-order reversal [16]. After quantization using an 8-bit ADC, 320-Gbps physical random bits are achieved by directly extracting 4 LSBs at 80-GHz sampling rate
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