Research On Key Technologies Of Advanced Coding Modulation In Short-distance Optical Communication System

The rapid development of big data,Internet of Things,cloud services,5G and other technologies has put forward new requirements for short-range optical communication application scenarios such as data center optical interconnection and optical access network,which require communication technologies with superior performance such as speed and bandwidth.At the same time,information security problems caused by brute force cracking and illegal eavesdropping also appear frequently,and information security problems are increasingly paid attention to.Advanced coded modulation technology can improve the frequency spectrum efficiency and achieve a higher transmission rate without increasing the system components.Chaotic perturbation technology can encrypt data in the physical layer to enhance the system security.In this paper,in order to improve the performance of information transmission and data security in short-range optical communication application scenarios,the realization and improvement of new coding modulation technology in short-range optical communication systems are studied.The specific research contents are as follows:（1）A Carrier-less Amplitude/phase Modulation（CAP）technique based on block-level labeling and graphene-shaped constellation is proposed.Combining Probabilistic Shaping（PS）and Geometric Shaping（GS）techniques,probabilistic shaping is realized by grouping markers to reduce signal transmission power.The new graphene-shaped constellation can significantly improve the space utilization rate of the constellation.The feasibility of this technology has been proved by the successful transmission experiment of graphene type PS 32-24 CAP with9.8 Gb/s on 25 km standard single-mode fiber.（2）A high security Orthogonal Chirp Division Multiplexing（OCDM）technique based on cellular neural networks and biological genetic coding（DNA）is proposed.Cellular neural network is used to implement 6 different dimensions of ultra-high security encryption,which is conducive to the improvement of system performance while maintaining low computational complexity.The transmitted bit data is interleaved according to DNA arithmetic rules,and the subcarrier frequency,symbol matrix and time are scrambled.The coding and perturbation rules adopt chaotic mapping random control,which enhances the robustness against malicious attacks.At the same time,the OCDM modulation technology is used to further optimize the system,improve the spectral efficiency of the system,and effectively improve the error performance and anti-interference ability of the system.（3）A high safety,high speed and short distance optical communication system based on the combination of advanced coding modulation technology and multi-core multiplexing technology is proposed.A 70 Gb/s transmission experiment was carried out on the proposed dynamic data disturbance OCDM secure transmission scheme in 2 km homogeneous weakly coupled seven-core fiber.In addition,Orthogonal Frequency Division Multiplexing（OFDM）signals are transmitted under the same conditions for comparison and verification.The results show that the key space of the proposed encryption scheme can reach 10¹¹⁷⁰.When the bit error rate is 10^-3,the receiving sensitivity of OCDM is 1.2 d B higher than that of OFDM.This scheme can not only meet the requirements of high-speed data transmission,but also effectively improve the security of the communication system.Compared with the traditional transmission scheme,the performance has been improved.