Research On Optical Orthogonal Frequency Division Multiplexing Systems Based On Probabilistic Shaping Technology

With the implementation and promotion of the “Broadband China” Strategy and“New Infrastructure Construction” Project,current communication systems and networks are confronted with increasingly severe challenges.For the purpose of green communication,system bandwidth and transmission rate should be efficiently enhanced,which can be regarded as significant indexes for the next-generation fiberoptic communication architecture.In order to investigate improvements of complexity,channel capacity,optical receiver power sensitivity(RPS)and signal tolerance to optical fiber nonlinearity,we introduce advanced high-order modulation formats like quadrature amplitude modulation(QAM),advanced optical multiplexing technology like orthogonal frequency division multiplexing(OFDM)and modulation-format optimization techniques of like probabilistic shaping(PS)into the short-reach optical interconnection and wavelength-division-multiplexing passive-optical-network(WDM-PON)with intensity modulation and direct detection.The primary research work and innovation of the paper are listed as follows.1.By further study and application of Gallager many-to-one mapping method,a generation scheme of high-order probabilistically-shaped signals following MaxwellBoltzmann distribution(MB)has been proposed and optimized,which employs lowdensity parity-check(LDPC)codes.The method is cost-saving since there is no extra PS redundancy,leading to efficient transmission.With turbo-like structure,bitinterleaved coded modulation scheme with iterative decoding is deployed at the receiver to efficiently address the ambiguity induced by overlapping symbols.The experiment employing PS-16/32 QAM OFDM demonstrates better BER performance.2.For complexity in the PS schemes based on arithmetic coding,a novel bitweighted distribution matching(BWDM)algorithm has been proposed for PS implementation,which enables asymmetric distribution of input bits by simple,finite and bit-level operations,and which,then,maps the binary codewords into constellation symbols with Gaussian distribution(GD)according to well-designed mapping rules.It is no need to change prevailing optical communication system structures,which reflects low computation and hardware complexity.In short-range optical interconnection and WDM-PON employing PS-16 QAM OFDM,bit error ratio(BER)performance and signal resistance against optical fiber nonlinear effects have been proved to be optimized.3.The principle of OFDM and its key techniques are given in detail.For the inherent issue that high peak-to-average power ratio(PAPR)of conventional OFDM can cause serious nonlinearity,efficient discrete Fourier transformation spread(DFT-Spread)algorithm with lower complexity has been proposed,and 4/16/32/64 QAM OFDM signals based on the method have been transmitted for performance investigation.According to the experimental results,RPS and signal tolerance to optical fiber nonlinearity can be improved.