Intensity Modulation Direct Detection Fiber Optical Transmission Based On The Probability Shaping Technique

With the rapid development of big data,cloud computing,and internet technology,the demand of capacity enhancement for inter-data center photonic interconnection is increasing steadily.Due to both the huge amount of users and the sensitivity to the implementation cost and the power consumption,the intensity modulation direct detection(IM-DD)fiber optic communication system based on higher order modulation format together with digital signal processing(DSP)is ideally desired for inter-data center photonic interconnection.How to achieve larger transmission capacity,higher bit-rate,and lower power consumption for IM-DD transmission system is currently a hot research topic worldwide.Probabilistic shaping(PS)technique can effectively enhance the capacity of transmission system under the power-constrained condition,and approach the theoretical limit of Shannon capacity.Therefore,my thesis is dedicated to apply the PS technique to N-lever pulse amplitude modulation(PAM-N),in order to improve the spectral efficiency(SE)and approach the theoretical capacity limit of the IM-DD transmission system.My research outcomes are summarized as follows:(1)We review the system configuration of IM-DD transmission,and explain the resource of transmission impairments and the corresponding compensation mechanism.Meanwhile,we put more emphasis on the higher-order modulation formats generation and detection schemes arising in the IM-DD transmission system.Moreover,several commonly-used digital equalizers for IM-DD transmission are explained and compared their performances.(2)In terms of the generalized mutual information(GMI),we theoretically investigate the operation principle of the PS technique,and calculate the GMI of the PS-PAM-N signal under the optimal Maxwell Boltzmann probability distribution,with the help of Monte Carlo simulation method.The GMI of the PS-PAM-N can effectively approximate the theoretical Shannon capacity,in comparison with the traditional PAM-N signal,under the optimal Maxwell Boltzmann probability distribution.Furthermore,a pairwise-optimized PS-PAM-8signal is proposed with the numerical simulation,whose GMI can effectively approximate the theoretical Shannon capacity,in comparison with the traditional PAM-8 signal.(3)We carry out comprehensive optimization and experimental verification for the proposed pairwise-optimized PS-PAM-8 signals.We numerically identify that,the pairwise-optimized PS-PAM-8 signal has a bit-error ratio(BER)performance improvement,in comparison with the traditional PAM-8 signal,under conditions of two probability mass distribution(PMD)function λ parameters.Finally,The experiment compares the size of GMI of pairwise-optimized PS-PAM-8 signas and traditional PAM-8 signals under back-to-back,2 km,and 5 km standard single-mode fiber(SSMF)transmission conditions.The optimal GMI gains of 80 Gbaud PS-PAM-8 signal are 0.5261 bit/symbol,0.857bit/symbol,and 0.993 bit/symbol,respectively.