Research On Four-dimensional Trellis Coding Modulation In High-speed Optical Communication System

With the rapid development of the information society,the emergence of a variety of emerging business such as 5G communication,HD live stream,artificial intelligence and automatic driving,the explosive growth of traffic has put forward higher requirements on the communication capacity and rate of optical communication transmission system.The fourdimensional modulation technology can increase the transmission capacity of the communication system,and can well balance the spectral efficiency and asymptotic power efficiency.Trellis coded modulation technology increases the Euclidean distance between constellation points,reduces the communication bit error rate.In order to solve the problem of traffic growth and broadband shortage,and save the construction cost of optical fiber and cable laying,the research of new coding modulation format has become a research hotspot at home and abroad.In this thesis,the system principles and key technologies of fourdimensional modulation technology and trellis coded modulation are studied,and novel four-dimensional trellis coded modulation scheme,ternary trellis coded modulation scheme and four-dimensional ternary trellis coded modulation scheme are proposed.The proposed schemes are simulated and analyzed,and the research results show that the proposed schemes reduce the signal BER and the average power required for signal transmission,and improve the reliability and transmission capacity of the optical communication system.The main research work of this thesis are as follows:(1)The TCM-SP-128QAM and TCM-SP-128TQAM modulation schemes are proposed.The proposed TCM-SP-128QAM scheme combines trellis coded modulation and four-dimensional modulation technology,using the set partitioning to expand the Euclidean distance between signal constellation points,and achieve four-dimensional modulation through the polarization characteristics of optical to obtain a certain coding gain with less increase in complexity.In order to further reduce the average power required for signal transmission,the TCM-SP-128TQAM modulation scheme is proposed,which uses the triangular quadrature amplitude modulated signal instead of rectangular QAM modulation to reduce the average power required to transmit the signal.The BER performance of the proposed scheme is studied in simulation.The results show that these two signal modulation schemes have high spectral efficiency and bit error rate performance.Compared with the traditional 4D modulation scheme 128-SP-QAM,the TCM-SP-128QAM and TCM-SP-128TQAM schemes obtained 2.63dB and 2.58dB gains,respectively at BER=1×10-3.(2)Ternary trellis coded modulation is proposed.This scheme optimizes the distribution rules of the traditional trellis coded modulation constellation diagram,takes the constellation diagram of triangular quadrature amplitude modulation signal as the set to divide the original constellation diagram,optimizes the traditional set partitioning into the ternary set partitioning,proposes the ternary set partitioning principle and the ternary convolutional code,and uses ternary convolutional codes for error correction coding in the GF(3).The multi-state 18-TTCM modulation formats are obtained by designing multiple ternary convolutional codes,and the performance of the 18-TTCM schemes is studied in simulation.The results show that the 9state-18-TTCM balances the signal BER and time complexity well.By changing the distribution rules of the constellation points of the regular 18-TTCM signal,two 18-TTCM constellation point ternary set partitioning optimization schemes are proposed to reduce the average power required for signal transmission and improve the system performance.The simulation results show that when OSNR=14dB,the BER of the 9state-18-TTCM scheme is 3.0×10-4.The BER of the two optimization schemes of 18-TTCM is respectively reduced to 1.39×10-5 and 8.33×10-6 compared with that of 9state-18-TTCM.(3)Four-dimensional ternary trellis coded modulation scheme is proposed.The scheme takes TTCM constellation diagram as original constellation diagram,and adopts the four-dimensional optical signal space is composed of the optical polarization states and the orthogonal in-phase components of each polarization state,and expands the two-dimensional signal to the four-dimensional optical signal space.A four-dimensional ternary set partitioning is proposed.The BER performance advantages of the 4D-18-TTCM coding modulation scheme are studied in simulation.The results show that 4D-18-TTCM has 0.27dB gain compared with 18TTCM,and 2.15dB gain compared with 128-SP-QAM at BER=1×10-3.