Optical chaos secure communication, a physical-layer encryption technology, represents an innovative solution addressing vulnerabilities in traditional cryptographic algorithms during the quantum computing and artificial intelligence era. This approach utilizes chaotic lasers as hardware-based “root keys”, combining high-speed capabilities, compatibility with existing fiber-optic infrastructure, and resistance to algorithmic decryption. In contrast to quantum key distribution, which encounters practical deployment challenges, optical chaos communication utilizes chaotic dynamics’ inherent unpredictability to facilitate secure data transmission and key exchange. This technology demonstrates strategic significance for national cybersecurity protection and the advancement of next-generation secure communication networks. This paper presents a comprehensive review of technological developments, challenges, and future directions in optical chaos secure communication, emphasizing chaotic laser generation, synchronization, communication frameworks, key distribution, and integrated chaotic light sources.

This review is structured into four main sections, each addressing a critical aspect of optical chaos secure communication.

The first section examines the fundamental principles of chaotic laser generation and synchronization. Various methods for generating chaotic signals are explored, including optical feedback, optical injection, and optoelectronic feedback. These techniques utilize the nonlinear dynamics of semiconductor lasers and optoelectronic oscillators to generate chaotic outputs with high complexity and unpredictability. The analysis includes distinctions between master-slave and common-signal-driven synchronization schemes, which are fundamental for ensuring transmitter and receiver synchronization in secure communication.

The second section focuses on the development of optical chaos communication systems, particularly those based on semiconductor lasers and optoelectronic oscillators. We review the progress in transmission rates, communication distances, and system integration, emphasizing the role of artificial intelligence (AI)-assisted digital signal processing in optimizing synchronization performance. For instance, AI-based models have been employed to compensate for signal distortions caused by transmission noise and to improve the accuracy of chaos synchronization. We also discuss the challenges associated with achieving high-speed communication over long distances, such as the impact of fiber dispersion and nonlinear effects on synchronization quality. Recent breakthroughs, including the use of broadband chaotic sources and advanced modulation techniques, have enabled data transmission rates of up to 100 Gbit/s over distances exceeding 100 km, demonstrating the potential of optical chaos communication for practical applications.

The third section examines the progress in chaos-based key distribution, where chaotic signals are used as physical entropy sources for secure key generation. We discuss various techniques for extracting random keys from synchronized chaotic signals, including chaos masking and random key distribution systems. These methods leverage the high correlation between chaotic signals generated by synchronized lasers to ensure that only the legitimate users can generate identical keys. However, challenges such as synchronization recovery time, key rate, and distribution distance remains a significant obstacle for high-speed and long-distance key distribution. Recent research has focused on reducing synchronization recovery time through the use of open-loop synchronization structures and optimizing key generation algorithms to improve key rates. Recently, key distribution rates of up to 0.75 Gbit/s over 160 km of optical fiber have been achieved, demonstrating the potential of chaotic key distribution in practical applications.

The fourth section highlights the advancements in chaotic light sources, which are critical for enhancing the performance of optical chaos communication systems. Significant progress has been made in broadening the bandwidth of chaotic signals through techniques such as external optical injection, mutual injection, and the use of high-nonlinearity fibers. Integrated chaotic lasers, including monolithic and hybrid integrated designs, have been developed to achieve compact and efficient chaotic sources. Novel laser structures, such as short-cavity DFB lasers, microcavity lasers, and long-cavity Fabry-Perot lasers, have demonstrated the ability to generate broadband chaotic signals with suppressed time-delay signatures. These advancements not only improve the complexity and unpredictability of chaotic signals but also pave the way for the miniaturization and practical deployment of chaos-based communication systems.

Despite substantial advances in enhancing optical chaotic systems’ performance and capabilities, several key challenges remain in fully realizing optical chaos secure communication’s potential for real-world applications.

The achievement of ultra-high-speed transmission with stable synchronization over long distances remains a significant challenge in optical chaotic communication. While transmission rates have improved, chaotic systems continue to face limitations from synchronization errors and environmental disturbances. AI-assisted signal processing, synchronization, and error correction demonstrate considerable potential for addressing these constraints, enhancing system efficiency and enabling faster, more precise synchronization. Furthermore, expanding key distribution capabilities remains essential for optical chaotic communication advancement. Although chaotic synchronization provides a robust foundation for secure key exchange, efficiency constraints arise from synchronization recovery time and distribution distance. Future research should prioritize reducing recovery time and improving key distribution system scalability for enhanced key exchange efficiency.

Looking ahead, optical chaotic communication presents transformative potential for secure communication systems, offering an alternative to conventional cryptographic methods. The ongoing integration of AI, improvements in chaotic laser technologies, and advances in key distribution techniques will expand the possibilities in secure optical communication. As communication networks become faster and more interconnected, optical chaos secure communication provides a promising solution to meet the increasing demand for robust, high-performance, and physically secure communication systems.