Research On Key Issues Of High-security OCDM Short-distance Optical Communication System Based On Chaotic Perturbatio

In recent years,with the rapid development of big data,Internet of Things,cloud computing and other technologies,data traffic is growing rapidly,and short-reach data center optical interconnection network is facing severe capacity expansion pressure.At the same time,massive data exchange also brings new challenges to the security of communication data transmission.In this paper,the data transmission in short-reach optical communication system is easy to be eavesdropped and interfered,and the system security performance and signal transmission security are discussed.In addition,in short-reach off-optical communication systems,orthogonal chirped division multiplexing(OCDM)multi-carrier modulation technology,high-dimensional constellation mapping technology and space division multiplexing technology have been widely studied and used as technologies to improve system transmission capacity and error rate performance.Therefore,based on the above technologies,this paper takes enhancing the security of short-reach optical communication system as the main research content,while taking into account the high performance and large capacity of the transmission system,and studies the high-security OCDM short-reach optical communication system based on chaos disturbance.The main research contents of this paper are as follows:(1)An OCDM short-reach optical communication system architecture based on intensity modulation direct detection(IM/DD)is proposed.Digital modulation of OCDM is realized by using discrete Fresnel transform(DFnT),and corresponding to its transformation characteristics,fast Fourier transform is adopted to realize fast modulation of OCDM,making its modulation complexity equivalent to orthogonal frequency division multiplexing(OFDM).In order to make the OCDM signal meet the transmission requirements in the IM/DD system,this paper also proposes a digital up-conversion technology based on OCDM,which moves the OCDM baseband signal to the frequency band through the digital carrier,and converts the complex OCDM baseband signal to the real OCDM band signal to achieve the transmission conditions in the IM/DD system.This scheme has high compatibility with existing OFDM systems,and can be well integrated into existing OFDM systems without major changes.In the experiment,the 20 Gb/s single-mode optical fiber OCDM signal transmission under the OCDM short-reach optical communication system architecture based on IM/DD was successfully realized.(2)A high-security OCDM-MDM short-reach optical communication technology based on time-frequency combined disturbance is proposed.Firstly,discrete Fresnel transform is used to realize the digital implementation of OCDM,then Lorenz chaotic model and Logistic chaotic model are combined to realize the joint time-frequency disturbance of orthogonal chirp subcarrier and orthogonal chirp symbol,and the OCDM signal is transformed by digital up conversion method and transmitted in the few-mode system.The chirped signal has good pulse compression and spread spectrum capability.The maximum chirped spread spectrum can be realized by using DFnT-based OCDM.The time-frequency joint perturbation of double chaos model can realize the large key space of 10144 and improve the security of information transmission.Through experiments,32 Gb/s OCDM encrypted signal transmission is realized on 5 km few-mode fiber,and OCDM has a maximum receiver sensitivity gain of 1.48 dB compared with OFDM at 1 × 10-2 bit error rate.(3)An OCDM multi-core multiplexing short-reach optical communication technology based on high-dimensional constellation perturbation is proposed.A new four-dimensional constellation map with constellation figure of merit(CFM)up to 1.17 is designed,a direct detection orthogonal chirped division multiplexing(DD-OCDM)optical transmission scheme based on four-dimensional constellation map is designed,and the OCDM signal transmission of 32.8Gb/s is realized on 2km seven-core fiber through experiments.The performance of the proposed constellation map is verified,and the four-dimensional hyperchaos model is used to perturbate it.The large key space of 10192 is realized.Under the condition of multi-core multiplexing and the bit error rate of 3.8 × 10-3,the receiver sensitivity of the proposed OCDM signal based on four-dimensional constellation map modulation has 0.59dB,3.26dB and 5.73dB gain compared with QPSK,16QAM and 16PSK,respectively.