A successful commercial deployment of quantum key distribution (QKD) technologies requires integrating QKD links into existing fibers and sharing the same fiber networks with classical data traffic. To mitigate the spontaneous Raman scattering (SpRS) noise from classical data channels, several quantum/classical coexistence strategies have been developed. O-band solutions place the QKD channel in the O-band for lower SpRS noise but with the penalty of higher fiber loss and can rarely reach beyond 80 km of fiber; another method is C-band coexistence with attenuated classical channels, which sacrifices the performance of classical channels for lower SpRS noise. In this work, a time-interleaving technique is demonstrated to enable the co-propagation of quantum and classical channels in the C-band without sacrificing either performance. By embedding QKD pulses in the gaps between classical data frames, the quantum channel is isolated from SpRS noise in both wavelength and time domains. C-band co-propagation of a polarization-encoding decoy-state BB84 QKD channel with a 100 Gb/s QPSK channel is experimentally demonstrated with quantum bit error rate (QBER) of 1.12%, 2.04%, and 3.81% and secure key rates (SKR) of 39.5 kb/s, 6.35 kb/s, and 128 b/s over 20, 50, and 100 km fibers, respectively. These results were achieved with the presence of classical launch power up to 10 dBm, which is at least one order of magnitude higher than reported works. We also demonstrated the co-propagation of a QKD channel with eight classical channels with total launch power up to 18-dBm (9-dBm per channel), which is the highest power of classical channels reported in C-band coexistence works.

翻译：量子密钥分发（QKD）技术的商业部署需要将QKD链路集成至现有光纤，并与经典数据流量共享同一光纤网络。为抑制经典数据信道产生的自发拉曼散射（SpRS）噪声，目前已发展出多种量子/经典共存策略。O波段方案将QKD信道置于O波段以降低SpRS噪声，但代价是光纤损耗较高且难以突破80公里传输距离；另一种C波段共存方案需衰减经典信道功率以抑制SpRS噪声，这降低了经典信道性能。本工作提出一种时间交织技术，可在不牺牲任何信道性能的前提下实现C波段量子与经典信道的共传输。通过将QKD脉冲嵌入经典数据帧的间隙，量子信道在波长域和时间域均与SpRS噪声隔离。实验展示了偏振编码诱骗态BB84 QKD信道与100 Gb/s QPSK信道在C波段的共传输：在20公里、50公里和100公里光纤上，量子比特误码率（QBER）分别为1.12%、2.04%和3.81%，安全密钥率（SKR）分别为39.5 kb/s、6.35 kb/s和128 b/s。这些结果是在经典信道发射功率高达10 dBm的条件下实现的，该功率值比已有报道高至少一个数量级。我们还演示了QKD信道与八个经典信道的共传输，其总发射功率达18 dBm（每信道9 dBm），这是C波段共存工作中报道的最高经典信道功率。