Rasearch On Probabilistic Shaping Coded Modulation Technology In High-speed Optical Communication System

The demand for higher data rates has exploded in recent years,which leading to a steady increase in throughput each year.With this overwhelming trend,Internet devices need to continuously deliver higher throughput to maintain these services,and even provide higher quality services.Today,fiber-optic communications systems form the backbone of the Internet and mobile networks,carrying 99%of the Internet's data traffic.Therefore,it is necessary to do research in high-speed optical communication and its key technologies.Under the condition of limited bandwidth,for example in wireless and optical communications,high frequency spectrum efficiency(SE)is a necessary condition for high data rate systems.Probabilitic shaping(PS)is a key technology for high-speed optical communication with flexible data rate.In addition,with the joint development of coded modulation(CM)technology,optical coherent detection technology and digital signal processing(DSP)technology,a more complex digital transceiver suitable for optical fiber channels has been realized.This enables the advanced high-order modulation format to carry more bits in each transmission symbol and improve the capacity and transmission rate of the system.Therefore,for the high-speed optical communication system,it is of great practical significance to do research in PS coded modulation technology and other related technologies.Based on the research of PS coded modulation and demodulation technology,this paper focuses on the key technologies in high-speed optical communication system.This paper emphasizes to research the PS star-16QAM and square-16QAM coherent detection scheme,radio-over-fiber(ROF)system with heterodyne detection scheme based on PS,and high-speed optical transmission schemes based on irregular PS,proving the advantages and potential of PS technology in high-speed optical communication field.The main research works and innovative points of this thesis are described as follows:1.The PS star-16QAM modulated coherent detection system scheme is proposed.The performance of star-16QAM and square-16QAM in PS and uniform scheme in coherent detection system is compared.Through numerical simulation and experimental verification,with the help of PS technology,the bit error ratio(BER)performance improvement of star-16QAM scheme is higher than that of square-16QAM scheme.Therefore,PS star-16QAM is better than PS square-16QAM scheme in terms of BER improvement.2.The PS heterodyne detection ROF system scheme is proposed.The feasibility of PS polarization division multiplexing(PDM)16QAM in the optical vector radio frequency(RF)signal generation system using heterodyne coherent detection is verified in the experiment.In the simulation,the PS 16QAM scheme can achieve better BER performance than the uniform 16QAM scheme.In the experiment,the PS 16QAM scheme can provide higher transmission rate when the PS 16QAM scheme and uniform 16QAM scheme have the same BER.In addition,fiber-wireless integration system with heterodyne coherent detection is demonstrated,and the ROF wireless distance is 40 m.The performance of PS in the 16QAM modulated ROF communication system is studied through experiment.3.A new scheme for generation of multiple-frequency optical millimeter-wave(mm-wave)signal in high-speed optical communication with parallel dual Mach-Zehnder modulators(MZMs)is proposed.This scheme uses one less optical filter and reduces the cost of transmitter.40,80 and 120 GHz mm-wave signals with the same transmitted data are generated.And the transmission of these mm-wave signals in 20 km single-mode fiber(SMF)is verified in the experiment.After 20 km SMF transmission,clear and wide opened eye diagrams of the 10 Gbaud on-off keying(OOK)signal carried by these mm-wave signals are measured,which proves that the proposed scheme has great potential in high-speed optical communication system.4.High-speed optical transmission schemes based on irregular PS are proposed.A novel flexible multi-rate passive optical network(PON)scheme employing ladder-type PS model to enable adjustable and flexible multi-rate access without changing the modulation format is proposed.A ladder-type PS PON with 64-ary carrierless amplitude and phase(CAP-64)modulation in an intensity-modulation and direct-detection(IM/DD)system over 25 km standard single mode fiber(SSMF)is experimentally demonstrated.The experiment realized multi-rate adaptation based on the ladder-type PS PON scheme.The results verify the proposed method can implement a rate feasible access even when the splitting ratio of power splitter changes dynamically.Besides,based on modified gaussian probability model,a novel enhanced CAP-9 modulation format PS scheme is proposed and experimentally verified.The experiment of 33.3 Gb/s CAP-9 signal transmission based on modified Gaussian type PS is successfully demonstrated over 25 km SSMF.The experiment results verify that the proposed scheme can improve the receiver sensitivity by 1.2 dB and 0.4 dB at BER of 3.8×10-3 compared with conventional uniform CAP-16 and conventional PS-CAP-16,respectively.The novel scheme is realized by overlapping the constellation points of uniformly distributed CAP-16.This research is an exploration of the new distribution model and provides a possible scheme for improving the receiver sensitivity of future optical communication systems.