Security enhancement of quantum noise stream cipher system based on optical temporal scrambling

•The proposed optical temporal scrambling scheme can be excellent adaptability to improve the security of quantum noise stream cipher system (QNSC) system.•By using an cascade Fabry-Perot cavities architecture to implement the masking of time domain features.•This work provides a security enhancement method for QNSC system to implement the capability of anti-eavesdropping for optical fiber communication, which could be favorable for the deployment of optical network infrastructure. In order to enhance security of QNSC signal, an optical temporal scrambling scenario which can avoid leaking synchronous clock parameters in QNSC system is proposed and experimentally demonstrated. In the proposed scenario, it utilized a cascaded FPCs to disturb time signature of 12.5 Gbps QNSC with 1024(210) intensity levels. The results indicate that, optical temporal scrambler cascaded 36 FPCs can spread the QNSC signal, resulting in the neighboring 12.5 bits of QNSC signal may be overlapped, which makes the signal look like noise both in intensity level and in time domain. Then, the descrambling process can be implemented by a matched filter corresponding to the optical temporal descrambling. Furthermore, by analyzing the scrambled QNSC signals, the power penalty caused by transmission for 50.8 km is about 3.22 dB. As for its actual effect, it greatly enhanced the security of the QNSC signal due to the concealment of time features.