This Letter proposes a high-security modulation scheme for optical transmission systems.By using multi-constellation shaping and asymmetric encryption, the information security can be enhanced and quantum computer cracking can be effectively resisted.Three-dimensional (3D) carrier-less amplitude phase modulation is utilized to superposition and transmit 3D signals.Experimental verification is conducted using a seven-core weakly coupled fiber platform.The results demonstrate that the proposed scheme can effectively protect the system from any illegal attacker.
This Letter proposes a high-security modulation scheme for optical transmission systems.By using multi-constellation shaping and asymmetric encryption, the information security can be enhanced and quantum computer cracking can be effectively resisted.Three-dimensional (3D) carrier-less amplitude phase modulation is utilized to superposition and transmit 3D signals.Experimental verification is conducted using a seven-core weakly coupled fiber platform.The results demonstrate that the proposed scheme can effectively protect the system from any illegal attacker.
In this Letter, we propose a highly secure three-dimensional orthogonal frequency division multiplexing (3D-OFDM) transmission scheme based on two-level noise masking key-accompanying transmission. The original signal is encrypted with a spherical constellation to ensure the system's security with a 4D Lorenz-like model. The key realizes two-level noise masking by introducing additional noise bits at the bit level and hiding in a noise-like spherical shell at the constellation level. Moreover, the proposed method of placing the key in the encrypted signal can simultaneously transmit the encrypted signal and the key. A 101.06-Gb/s 3D-OFDM encrypted signal with the proposed scheme over a 2-km 7-core fiber experiment was successfully implemented. Experimental results show that the security performance of the system can be guaranteed under the conditions of partial key leakage and key misplacement at the illegal receiver. At the same time, the key masking degree (KMD) of the proposed two-level noise masking can reach 3267, which effectively guarantees the safe transmission of the key.
This paper proposes an odd-order quantum noise-like stream cipher scheme based on joint index modulation (JIM) constellation shaping. By utilizing subcarrier index modulation and dual-mode index techniques, additional information is transmitted through the combination distribution of silent subcarrier positions and constellation modes associated with subcarriers. An odd-order 9QAM signal is constructed, and by optimizing the index rule, constellation shaping is achieved while transmitting more information, increasing the distribution of constellation points within the signal. A 4D hyper-chaotic system is employed to implement multi-dimensional disturbances, including bitwise XOR of the original signal, subcarriers, symbols, and elevate the constellation order. Furthermore, the scheme performs upsampling on the chaotic system's initial values and actively introduces noise bits, which are appended to the initial signal as a basis state to enable key-accompanying transmission. Ultimately, the constellation-shaped 9QAM signal is escalated to a 576QAM signal with constellation shaping features. Experimental results demonstrate the successful transmission of a 2.94 Gb/s quantum noise stream signal over a 25 km single-mode fiber intensity modulation direct detection (IMDD) system. The experimental results show that the proposed JIM-576QAM1 signal provides a 0.7 dB gain at Forward error correction (FEC) = 3.8 × 10 −3 compared to random distribution of the two constellation modes. The proposed scheme maintains a bit error rate (BER) of 0 for key transmission, and abruptly increases to 0.5 in the event of misalignment, indicating a high sensitivity and accuracy of the system with respect to the key. At varying received optical power, the number of masked signal power remain consistent at 20480, and the detection failure probability stays around 1, demonstrating the stability and security of the proposed quantum noise stream encryption scheme. With a key space as large as 10 149 , the scheme can effectively counter brute-force attacks from unauthorized receivers. The proposed scheme exhibits high reliability and security, making it a promising candidate for future optical access applications.
In recent years, the self-homodyne coherent (SHC) system and the constellation shaping (CS) technique have drawn considerable attention due to their abilities to further improve the transmission capacity for various scenarios. From the security point of view, the CS technique and the SHC infrastructure also provide new dimensions for encryption. We propose a high-security and reliable SHC system based on the CS technique and the digital chaos. With a four-dimensional hyperchaotic system, chaotic sequences are generated and used for the exclusive or operation, chaotic constant composition distribution matching, phase disturbance, and optical-layer time-delay disturbance. Moreover, 64-ary circular quadrature amplitude modulation (64CQAM) format is adopted for transmission due to its advantages of sensitivity to phase noise, immunity to conventional digital signal processing, and ability of time-mismatch masking, which is verified by simulation in a SHC system. Last, we conduct an experimental verification in a 20GBaud probabilistically shaped 64CQAM SHC system. Consequently, with a large-linewidth laser source, optical-layer security can be protected by time mismatches of tens of picoseconds. And the digital-layer security is protected by an enormous key space of 10 127 . The proposed scheme can provide reliable real-time encryption for the optical fiber transmission, serving as a potential candidate for the future high-capacity inter/intra-datacenter security interconnect.
This paper proposes a high-security probabilistic shaping 16-7QAM mapping method via constellation-level chaotic tagging. A novel, to the best of our knowledge, constellation-level chaotic tagging rule is devised that re-maps the original 16 signal points, each encoded by 4 bits, onto predefined 3-bit modulation symbols. Simultaneously, a Lorenz chaotic system is employed to generate a chaotic sequence, from which a 2-bit tag corresponding to each 3-bit modulation symbol is extracted to form the constellation-level chaotic tag. Subsequently, each signal point is combined with a 2-bit tag generated by a Lorenz chaotic system to form the final output consisting of 7 signal points. Experimental validation over a seven-core fiber transmission system shows that, at a bit error rate of 3.8 × 10 −3 , the proposed probabilistic shaping 16-7QAM constellation achieves a 0.49 dB improvement in receiver sensitivity compared with conventional 16-QAM. Moreover, the encryption scheme has almost no impact on the transmission performance of the probabilistic shaping signal itself. Additionally, the key space of the scheme reaches 10 105 , effectively ensuring physical layer security. The proposed method exhibits robust performance and strong security, enhancing both the transmission performance and security of the system.
In this article, we propose a high-security transmission scheme of power division 3-D carrier-less amplitude and phase (PD-3D-CAP) based on polling-permutation encryption and noise masking key distribution. By implementing the 6D Lorenz digital chaotic system, we scramble the 3D-CAP signal, effectively enhancing the security performance of the system. In our scheme, the proposed noise-masking key distribution can be considered noise-like and transmitted along with the chaotic encrypted signal in the channel. It is important to note that our mechanism also enables uninterrupted authentication and decryption at the receiver to handle continuous key updates. We experimentally demonstrate the transmission of a 12.67 Gb/s 3D-CAP signal over a 2 km 7-core fiber using the proposed scheme. The scheme allows for simultaneous key transmission without a significant increase in the bit error rate. Additionally, we compare the performance of the PD-3D-CAP scheme to that of the PD-2D-CAP scheme, and observe a sensitivity gain of 0.4 dB with the proposed PD-3D-CAP scheme.
This study investigates a multi-stage digital phase-encryption scheme designed for secure coherent optical communication. While the proposed method is implemented in DSP and can be modeled as a software-level stream cipher, it is explicitly co-designed with and tightly coupled to the physical-layer modulation structure. Unlike conventional XOR-based bitwise schemes, the encryption is applied to the symbol phase domain. It is integrated into the transmitter's modulation process, enabling symbol-level security evaluated in conjunction with transmission physics. By applying K-level phase-shift secret keys toM-ary quadrature amplitude modulation (QAM) signals, this method increases the number of secret-key bits per symbol without altering the signal constellation in its baseline configuration. This approach enhances encryption strength while maintaining signal integrity and reducing quantization overhead in phase-only operation. Experimental evaluations on nonlinear optical transmission channels confirm that baseline digital phase encryption preserves Q-factor stability under self-phase modulation, cross-phase modulation, and four-wave mixing. The proposed scheme ensures error-free transmission at forward error correction thresholds, effectively preventing eavesdroppers from reconstructing symbols under worst-case observation conditions. Additionally, simulations analyzing generalized mutual information and quantization errors demonstrate that the encryption scheme can minimize signal-to-noise ratio penalties, even when employing high-order QAM formats with limited digital-to-analog and analog-to-digital conversion resolutions. As an optional extension, we also analyze pseudo-quantum-noise-based IQ spreading and explicitly quantify the associated trade-off between additional noise masking and increased sensitivity to quantization. These findings position multi-stage digital phase encryption as a practical and power-efficient modulation-layer encryption technique whose behavior is systematically characterized under realistic nonlinear channel and hardware constraints, rather than as an entirely new cryptographic primitive.