Researc H And Design Of Probabilistic Shaping And Relative Key Techniques For Coded Modulation In Optical Coherent Communication Systems

With the rapid growth of the bandwidth requirements of Internet communication,high-speed and large-capacity coherent optical communication systems have been widely used.The coded modulation technology which was designed and combined to improve the system capacity without expanding the spectrum occupancy,and has received more and more attention.Probabilistic shaping combined with coded modulation can further expand the OSNR tolerance and increase the signal transmission distance without affecting the coding and modulation performance.However,the post probabilistic shaping schemes have the disadvantages of low efficiency,poor flexibility,and high implementation complexity.In this article,the deep research on the probabilistic shaping coding scheme in coherent optical transmission coded modulation system and the combination of probabilistic shaping and coded modulation.The main research work is as follows:Firstly,a high-gain probabilistic shaping coded modulation scheme is proposed for the problem of low probability probabilistic coding.The high-gain probabilistic shaping coding scheme in the proposed scheme uses a novel symbol mapping method to match the distribution of the input information at the bit level.At the same time,the bit-interleaving scheme of input distribution preservation is used,and the proposed probability shaping scheme is combined with the traditional BICM uniform distributed coding modulation scheme to further expand the OSNR tolerance.According to theoretical analysis,efficiently,the high-gain probabilistic shaping coded modulation scheme uses 6.7%redundancy to increase the minimum average Euclidean distance of the constellation points by 14%.The optical transmission simulation results show that under the condition of the same average transmission power and the same code rate,the improved gain probability shaping scheme can bring OSNR coding gain of 0.28dB when the post BER is 1E-5.In the optical fiber spans simulation results,when the mutual information is 3.2 bits/symbol,the transmission distance of the high-gain probability shaping scheme can be increased by 8.2%.Compared with the reported probabilistic shaping scheme,the distance gain caused by unit redundancy is increased by 3 9%.Secondly,to solve the problem that in the elastic optical net\Awork based on the rate adaptation scheme of modulation format change,the hardware implementation complexity is high and the information rate adjustment granularity is large,we propose a rate adaptive probability shaping coding modulation scheme".The scheme changes the transmission probability of constellation points of different powerlevels by means of inverse-marking",and achieves matching of information input distribution.At the same time,because different redundancy can bring different degrees of distribution matching effect,the scheme achieves the adjustment of the information rate from 0%to 16.7%by introducing redundancy of 0%to 20%.The hardware complexity achieves the effect of maximizing the use of channel capacity.When the amount of redundancy used is between 4%and 20%,the modulation granularity is 0.7%to 6.8%of the system baud rate.The optical transmission simulation results show that,when 20%redundancy is used,the rate adaptive probability shaping coding modulation scheme is smaller than the traditional coding modulation scheme without probability shaping when the error rate after decoding is 1E-5.Get an OSNR gain of up to 1.6dB.Thirdly,in order to verify the feasibility of the proposed high-gain probability shaping coding modulation scheme and "rate adaptive probability shaping coding modulation scheme",we set up an offline polarization multiplexing coherent optical transmission experimental system to separately implement the proposed scheme.Experimental verification.The experimental modulation format is PM-16QAM and the baud rate is 12 GBaud.At the same time,with the statistical method of statistical error symbol rate,the influence of OSNR measurement error on the experimental results can be reduced.In the"high-gain probability shaping coding modulation scheme"experiment,when the error rate after decoding is 1E-4,the high-gain probability shaping coding modulation scheme obtains additional compared to the conventional coding modulation scheme with the same total redundancy:An OSNR gain of about 0.15 dB;in the"rate adaptive probability shaping coding modulation scheme"experiment,when the probability shaping coding redundancy is 20%,7.7%,and 2.2%,the code rates are 0.694,0.774,and 0.815,respectively.A uniform distributed coding modulation scheme with a probability shaping code rate of 0.833 is not used,and when the bit error rate after decoding is 1E-5,OSNR gains of 1.7 dB,1.3 dB,and 0.6 dB are obtained,respectively.The experimental results verify the feasibility of the two schemes.Under the experimental conditions,both schemes achieve a good probability of shaping gain.