Protecting confidential high speed optical signal transmission at the lowest physical layer is a critical challenge for modern fiber-optic communication systems. In this paper, we experimentally demonstrate a novel synchronous privacy enhanced chaotic temporal phase en/decryption scheme for high-speed physical layer secure optical communication. A remote chaos synchronization architecture relying on common source signal driving and private response hardware modules comprising of dispersive components and slave lasers is employed to generate synchronized private chaotic en/decryption signals, and simultaneously suppress residual driving-response correlation for enhancing the security. A proof-of-principle demonstration by secure transmission of a 28 Gb/s on-off-keying modulated confidential signal over 100 km single mode fiber link based on the private chaotic temporal phase en/decryption scheme is successfully achieved. The demonstrated hardware optical en/decryption approach may provide a promising way towards future ultra-high speed physical layer secure optical communication systems.

Chaotic optical communication based on conventional external cavity semiconductor laser is a very promising solution for physical layer secure communication. However, the intrinsic time delay signature (TDS) associated with the external cavity length and the potential direct linear filtering (DLF) or synchronization utilization attack greatly threaten the system security. In this work, we propose and numerically demonstrate a novel scheme for TDS suppression and security enhancement of chaotic optical communication based on external temporal self-feedback hardware encryption and decryption. In this scheme, the confidential chaotic modulated signal is temporally scrambled in the time domain by two optical dispersion components and an electro-optic self-feedback phase modulation loop between them, which simultaneously conceal the TDS and enhance the security against malicious attacks. Proof-of-principle demonstration for a security enhanced chaotic optical communication system with error free transmission is successfully achieved. The proposed scheme may provide a promising way for pure-hardware based physical secure chaotic optical communication systems.

Achieving photonic layer security at the lowest network layer to supplement the upper layer digital cryptography in fiber-optic networks is a constant pursuit but a critical challenge. In this Letter, we propose and experimentally demonstrate a high-speed photonic-layer secure optical communication system based on a novel, to the best of our knowledge, common noise driven synchronous private temporal phase en/decryption scheme, which is capable of supporting high-order modulation formats and enhancing security. A record high bit rate of 56 Gb/s 4-level pulse amplitude modulation (PAM4) confidential signal is successfully encrypted and decrypted by remotely synchronized private noise-like en/decryption signals after secret transmission over 20 km of optical fiber with a bit-error-rate (BER) lower than the hard-decision forward error correction (HD-FEC) limit. The demonstrated scheme may provide a promising way for future ultrahigh-speed photonic-layer secure optical communication.

In this paper, a novel phase encryption scheme based on a dual-loop electro-optic self-feedback structure is proposed for time-delay signature (TDS) concealment. As for a conventional single-loop feedback structure, the TDS is extremely vulnerable to exposure in the common link, resulting in a fatal weakness in the entire security system, whereas, the introduction of an additional feedback branch, brings about the mutual dynamics between the phase feedbacks, and effectively solves the problem. The modulation depth and dispersion values, which are two crucial variables affecting TDS concealment, are investigated in detail. In principle, the scheme is verified to have better robustness, more security, and can supply large key space. Error-free transmission of high-speed signals is possible. Thanks to the aforementioned benefits, the dual-loop electro-optic structure proposed could inspire fresh ideas for secure optical communication systems in the future.

With the widespread application of big data, the amount of data transmitted through optical networks has been increasing dramatically. Correlated random bit generation (CRBG) is one of the key technologies in secure communication systems to ensure security performance and transmission efficiency. We propose and demonstrate a CRBG scheme based on a Mach–Zehnder modulator (MZM) electro-optic feedback loop to improve the security and speed of communication systems. In this scheme, common-signal-induced synchronization is accomplished to generate wideband complex physical entropy sources, and a private hardware module is employed to perform post-processing and nonlinear transformation of the synchronized signal. The simulation results show that the effective bandwidth of the output chaotic signal is significantly increased to 27.76 GHz, and high-quality synchronization with a correlation coefficient of over 0.98 is reached. A high-rate CRBG of up to 5.3 Gb/s is successfully achieved between two synchronized wideband physical entropy sources, and the hardware key space is enhanced to ∼242, which greatly improves the privacy of physical entropy sources. The proposed scheme provides a promising approach for high-speed private CRBG, which is expected to be used in high-speed secure key distribution and optical communication systems.