Channel power management of 400†G transmission system based on C6T + L6†T spectrum and QPSK modulation format.

In the 400 Gbit/s transmission system based on C + L band spectrum and QPSK modulation format, the short-wavelength signal power will be shifted to the long-wavelength signal due to the presence of the stimulated Raman scattering (SRS) effect, which will seriously affect the performance of the transmission system as the transmission span accumulates. The solution is to set the gain and gain slopes of the C-band amplifier and L-band amplifier appropriately at each optical amplifier site, and adjust the signal power of each channel through the WSS at the transmitting end and the WSS at the DGE site, so that the flatness of the channel power at the receiving end can be controlled in a reasonable range, thus guaranteeing the transmission performance of the system. However, the system fault will destroy the originally set channel power, which will seriously affect the transmission performance of the system. In this paper, filling channel device combined with output power locking of amplifiers used in a 400 Gbit/s system based on C + L band and QPSK modulation format to provide the protection for the system is proposed and demonstrated for the first time, which gives different solutions for sudden fault at different locations of the system, and provides a reference for the channel power management of multi-band optical transmission systems in the future.

High-security SCMA-OFDM multi-core fiber transmission system based on a regular hexagon chaotic codebook.

Sparse code multiple access (SCMA), a new code-domain non-orthogonal technology in the fifth-generation mobile communication (5G), can be modulated by orthogonal frequency division multiplexing (OFDM) to improve the link quality of a single user. In this paper, a high-security SCMA-OFDM multi-core fiber transmission system based on a regular hexagonal chaotic codebook is proposed for next-generation passive optical network (PON). The whole encryption process consists of a regular hexagon chaotic codebook design and frequency domain block scrambling. In designing the regular hexagon chaotic codebook, the optimization of constellation points on orthogonal resources are considered as the starting point. Firstly, the chaos factor generated by the four-dimensional Rossler chaos model is deployed to disturb the mother constellation, and then the corresponding chaotic book is formed by rotating the mother constellation and multiplying the sparse matrix. The designed codebook logically avoids the degradation of transmission performance caused by the rough scrambling of codebook constellation, to find a balance between codebook disturbance and bit error rate (BER). The security and reliability of the transmission system have been verified by performing 42 Gb/s encrypted SCMA-OFDM data transmission experiments in a 2km multi-core fiber. The key space of the encryption scheme can reach 10178, which effectively ensures the security of the transmission system. Furthermore, the performance of the transmission system with a regular hexagon chaotic codebook is improved by 2.5 dB compared with the traditional codebook when the BER is 1 × 10-3. Moreover, the SCMA-OFDM-based transmission architecture and the detection effects of different multi-user detection algorithms in the SCMA-OFDM multi-core fiber transmission system are also studied.

Mode division multiplexing chaotic encryption scheme based on key intertwining and accompanying transmission.

A mode division multiplexing (MDM) chaotic encryption scheme based on key intertwining and accompanying transmission is proposed in this paper. Based on the weakly coupled few-mode fiber (FMF), data and time-varying keys can be accompanied by transmission in two modes, LP01 and LP11, respectively. In order to generate a new key, the current key is XORed with all of the keys from all the preceding moments, one by one. To implement chaotic masking in the digital domain, the three chaotic sequences corresponding to the new key are adopted to encrypt the data at the constellation phase, data symbol block, and subcarrier levels. An 8.89 Gb/s encrypted 16QAM-OFDM signal transmission over 1 km weakly-coupled FMF is experimentally demonstrated. The receiver with the correct key can recover the data normally, while the BER of the illegal receiver remains around 0.5. In the case of the key transmission bit rate of 1 Gb/s, the cracking efficiency threshold of the time-varying key encryption scheme is 5.21 × 106 times that of the time-invariant key encryption scheme, which suggests that the proposed work is a promising candidate for future physical layer security.