Covert Key Generation and Distribution Based on Gain Switching Laser

This article proposes and experimentally demonstrates a covert key distribution scheme based on the phase fluctuation of a gain-switched laser diode (GSLD). The gain-switched pulse is used to generate the covert signal through spectral broadening and temporal spreading. The amplified spontaneous emission (ASE) light is used to generate ASE noise in the public channel. Eavesdroppers cannot perceive signals hidden in the public noise. The experimental results show that the correlation coefficient of the key waveforms reaches 0.95, and the scheme’s key generation rate (KGR) reaches 1.88 Gbit/s through a 25 km single-mode fiber (SMF). Moreover, the binary bitstreams have passed the NIST statistical test suite. The covert key distribution scheme proposed in this article provides an efficient way for the method of “one-time-pad” key distribution in high-speed optical communication systems.