Tanizawa Ken, Futami Fumio
Opt Express. 2021 Mar 29;29(7):10451-10464. doi: 10.1364/OE.418302.
A record-long 10,118-km fiber transmission with physical layer encryption is demonstrated utilizing a Y-00 cipher based on signal masking by quantum (shot) noise. The Y-00 cipher enables symmetric-key data encryption to ensure the security of the physical layer of optical communications. Irreducible secrecy without significant negative impact on transmission performance is achieved by the synergistic effect of combining seed-key-based high-order modulation and truly random shot noise inevitable in optical detection. This paper reports a comprehensive study of applying a phase-shift-keying (PSK) Y-00 cipher for ultra-long haul fiber transmission. Theoretical analysis shows that security-enhanced transmission over transoceanic-distance (>10,000 km) fiber is feasible when the quadrature PSK data signal is encrypted by converting to a PSK signal with 2 levels. Subsequently, 10,118-km standard single-mode fiber transmission of 48-Gbit/s line-rate dual-polarization PSK Y-00 cipher with 2 levels is experimentally demonstrated. An adequate signal quality above the Q-factor threshold of soft decision forward error correction is achieved together with sufficient signal masking by shot noise, yielding balanced transmission performance and high security in an ultra-long-haul PSK Y-00 cipher transmission system.
利用基于量子（散粒）噪声信号掩蔽的Y-00密码，演示了长达10118公里的具有物理层加密的光纤传输。Y-00密码实现了对称密钥数据加密，以确保光通信物理层的安全。通过基于种子密钥的高阶调制与光检测中不可避免的真正随机散粒噪声的协同效应，实现了不可约保密性，且对传输性能无显著负面影响。本文报道了将相移键控（PSK）Y-00密码应用于超长距离光纤传输的全面研究。理论分析表明，当正交PSK数据信号通过转换为具有2个电平的PSK信号进行加密时，跨洋距离（>10000公里）光纤上的增强安全性传输是可行的。随后，通过实验演示了488-G>10000公里标准单模光纤上48-Gbit/s线速率双偏振2电平PSK Y-00密码的传输。在软判决前向纠错的Q因子阈值以上实现了足够的信号质量，同时散粒噪声提供了足够的信号掩蔽，在超长距离PSK Y-00密码传输系统中实现了平衡的传输性能和高安全性。
