Tone reservation encryption scheme based on transformer-long short-term Memory in photonics-aided fiber wireless seamless integrated transmission system.

In response to the issues of peak-to-average power ratio (PAPR) and dynamic degradation in multi-carrier chaotic encryption, this paper proposes the tone reservation (TR) encrypted scheme based on transformer-long short-term (LSTM), to achieve physical-layer encrypted transmission in the fiber wireless seamless integrated system. The proposed scheme integrates 23 large-scale 3D chaotic models with a hybrid transformer-LSTM neural network architecture. This combined framework generates 3D chaotic sequences via nonlinear predictive modeling, which are then applied to encrypt the original data at the physical-layer. The 3D chaotic sequences generated by the neural network are applied to TR selection, effective subcarrier scrambling, and whole subcarrier scrambling respectively. This scheme achieves physical-layer encryption while reducing the PAPR of the communication system, with an average reduction of 1.47 dB. The R (R-squared) of the chaotic sequence predicted by the neural network reaches over 0.99, and the root mean square error (RMSE) reaches 0.066. Compared with traditional single-characteristic chaotic sequence prediction, the proposed prediction scheme possesses multiple chaotic source characteristics, enabling it to resist nonlinear dynamical degradation issues. In this paper, the transmission of 12Gbaud quadrature phase shift keying (QPSK) signal at 20.6 Gb/s in 4-meter fiber wireless seamless integrated transmission system is experimentally demonstrated by experiments, and the performance of the system is analyzed. The encrypted signal meets hard decision forward error correction (HD-FEC) threshold @3.8×10 at the legal receiver, and the minimum bit error rate (BER) can reach 2.1×10. At the HD-FEC@3.8×10, the sensitivity of the input optical power (IOP) is improved by 0.45 dB after reserved subcarrier optimization. At the illegal receiver, without the correct key, the BER exceeds 0.4, and the original data cannot be decrypted, effectively preventing illegal attacks. The experimental results demonstrate that this scheme can secure data transmission from the very foundation of the communication system, indicating significant application potential in future fiber wireless seamless integrated secure communications.