*Article* **Key Distribution Scheme for Optical Fiber Channel Based on SNR Feature Measurement**

**Xiangqing Wang <sup>1</sup> , Jie Zhang 1,\*, Bo Wang <sup>1</sup> , Kongni Zhu <sup>1</sup> , Haokun Song <sup>1</sup> , Ruixia Li <sup>2</sup> and Fenghui Zhang <sup>2</sup>**


**Abstract:** With the increase in the popularity of cloud computing and big data applications, the amount of sensitive data transmitted through optical networks has increased dramatically. Furthermore, optical transmission systems face various security risks at the physical level. We propose a novel key distribution scheme based on signal-to-noise ratio (SNR) measurements to extract the fingerprint of the fiber channel and improve the physical level of security. The SNR varies with time because the fiber channel is affected by many physical characteristics, such as dispersion, polarization, scattering, and amplifier noise. The extracted SNR of the optical fiber channel can be used as the basis of key generation. Alice and Bob can obtain channel characteristics by measuring the SNR of the optical fiber channel and generate the consistent key by quantization coding. The security and consistency of the key are guaranteed by the randomness and reciprocity of the channel. The simulation results show that the key generation rate (KGR) can reach 25 kbps, the key consistency rate (KCR) can reach 98% after key post-processing, and the error probability of Eve's key is ~50%. In the proposed scheme, the equipment used is simple and compatible with existing optic fiber links.

**Keywords:** key distribution; signal-to-noise ratio; reciprocity; key consistency rate
