Opt Lett. 2023 Jul 1;48(13):3547-3550. doi: 10.1364/OL.490057.
Secure key distribution (SKD) schemes based on the interaction between a broadband chaotic source and the reciprocity of a fiber channel exhibit reliable security and a high key generation rate (KGR). However, under the intensity modulation and direct detection (IM/DD) architecture, these SKD schemes cannot achieve a long distribution distance due to the limitations on the signal-to-noise ratio (SNR) and the receiver's sensitivity. Here, based on the advantage of the high sensitivity of coherent reception, we design a coherent-SKD structure where orthogonal polarization states are locally modulated by a broadband chaotic signal and the single-frequency local oscillator (LO) light is transmitted bidirectionally in the optical fiber. The proposed structure not only utilizes the polarization reciprocity of optical fiber but also largely eliminates the non-reciprocity factor, which can effectively extend the distribution distance. The experiment realized an error-free SKD with a transmission distance of 50 km and a KGR of 1.85 Gbit/s.
基于宽带混沌源相互作用和光纤互易性的安全密钥分配（SKD）方案具有可靠的安全性和高密钥生成速率（KGR）。然而，在强度调制和直接检测（IM/DD）架构下，由于信噪比（SNR）和接收器灵敏度的限制，这些 SKD 方案无法实现长距离分配。在这里，基于相干接收的高灵敏度优势，我们设计了一种相干-SKD 结构，其中宽带混沌信号局部调制正交偏振态，单频本振（LO）光在光纤中双向传输。所提出的结构不仅利用了光纤的偏振互易性，而且还大大消除了非互易性因素，这可以有效地延长分配距离。实验实现了无差错的 SKD，传输距离为 50km，KGR 为 1.85Gbit/s。
