Abstract: Quantum-Noise Randomized Cipher (QNRC) is a kind of physical-layer encryption technology based on Heisenberg uncertainty principle, which can be applied to high-speed, large capacity and long-haul optical fiber communication network. In order to solve the problem that the modulation and demodulation of M-ary Y-00 ciphertext signal in QNRC system is limited by the ADC chip with high sampling rate and high conversion depth, this paper proposes a method to modulate and demodulate Y-00 ciphertext signal by using multiple phase modulators (PM) in series, and the performances of the proposed scheme is verified by using VPItransmission Maker Optical Systems simulation software. The simulation results show that, the PSK-QNRC system at 10 Gbit/s over 1000-km optically amplified links, where the number of ciphertext states are attained to 126 is realized based on the series structure of multiple PM; Reducing the mesoscopic power of the ciphertext quantum state can improve the security level of QNRC system, but it will damage the transmission performance of the system at the same time. It is very important to select the appropriate mesoscopic power to optimize the security and reliability of QNRC system.

Key words: optical communications, anti-interception communication, quantum-noised randomized cipher, Y-00 protocol