A novel secure optical 3D probabilistic shaping carrier-less amplitude and phase (3D-PS-CAP) system based on spherical constellation masking is proposed in this letter. In order to improve the bit error rate (BER) performance of the system, probabilistic shaping (PS) is given full play. By employing different masking vectors in different cubes, masking for the constellation points is realized. We successfully conducted an experiment demonstrating 6.5 Gb/s 3D-PS-CAP-16 data transmission over 25 km standard single-mode fiber (SSMF). At BER of $1\times 10^{ {-3}}$ , the received sensitivity of 3D-PS-CAP-16 is improved by 1 dB. Moreover, with spherical constellation masking, a key space size of $9.5\times 10^{ {139}}$ is achieved to bring about high security and good encryption performance, suggesting broad application prospects in future short-range secure communications.

中文翻译：

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基于球形星座掩蔽的安全光学 3D 概率整形 CAP 系统

在这封信中提出了一种基于球形星座掩蔽的新型安全光学 3D 概率整形无载波幅度和相位 (3D-PS-CAP) 系统。为了提高系统的误码率（BER）性能，充分发挥了概率整形（PS）的作用。通过在不同的立方体中采用不同的掩蔽向量，实现了对星座点的掩蔽。我们成功地进行了一项实验，演示了 6.5 Gb/s 3D-PS-CAP-16 数据在 25 公里标准单模光纤 (SSMF) 上的传输。在 BER $1\times 10^{ {-3}}$ ，3D-PS-CAP-16的接收灵敏度提高了1dB。此外，使用球形星座掩蔽，关键空间大小为 $9.5\times 10^{ {139}}$ 实现了高安全性和良好的加密性能，在未来的短距离安全通信中具有广阔的应用前景。