Journal of Lightwave Technology

High-Speed Real-Time Random Bit Generation Based on a Modeless Raman Fiber Laser

Yanxin Li, Xuewen Shu

Published Apr 21, 2026• 0 citations

Abstract

True random numbers are essential for cryptography and secure communications. Algorithmically generated pseudo-random numbers lack true physical randomness, while conventional lasers as physical entropy sources introduce time-delay signatures (TDS) and require complex post processing. To address this challenge, this study presents a high speed, real-time true random bit generator utilizing a modeless Raman fiber laser (RFL). A modeless RFL was constructed using an ultra-low reflectivity (-27 dB) fiber Bragg grating (FBG) and a high-reflectivity FBG serving as cavity mirrors. The laser delivers stable modeless Raman lasing within the pump power range of 5 W to 10 W. Compared with multilongitudinal-mode operation, the modeless laser exhibits significantly lower temporal coherence. By truncating the four least significant bits of the 8-bit digitized temporal intensity signal from the modeless RFL, random bit sequences were generated at a rate of 320 Gbps. The resulting random bit stream shows a uniform distribution of bits 0 and 1, its autocorrelation function contains no TDS, and it successfully passes the NIST statistical test. In contrast, the same generation method fails to produce qualified random bits when applied to the Raman fiber laser operating in the multilongitudinal-mode regime. The demonstrated modeless RFL system combines real-time operation, high speed, and stability, offering a robust physical entropy source for cryptographic and secure communication applications.

DOI: 10.1109/jlt.2026.3686262

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