Investigation On PS-QPSK Modulation And Coded Modulation Techniques In Ultra-high Speed Coherent Optical Transmission Systems

In recent years,the four-dimensional modulation format has gained widespread attention in academia and industry.Among them,a typical four-dimensional modulation format polarization switched quadrature phase shift keying(PS-QPSK)is considered to be the most power efficient modulation format,accorded with the "green communication"purposes proposed by the industry.With the growing of dynamic and bursty network traffic,flexible optical network has become an important mean to optimize network resources allocation,which requires the modulation formats has the flexibility to adjust capacity spectrum efficiency,transmission reach and so on.Coded Modulation technology has become one of the key enabling technologies for large capacity high order modulation coherent optical transmission system.This dissertation focuses on PS-QPSK modulation and its coherent receiver digital signal processing(DSP)algorithms,fine-grained elastic multi--dimensional modulation method and the design of high coding gain multilevel coded modulation scheme for ultrahigh speed coherent optical communication system.The main research work is as follows:1.For the most power efficient four-dimensional modulation format PS-QPSK in 100Gbps coherent optical transmission system,a PS-(D)QPSK system implementation which compatible with PM-(D)QPSK system is designed,mainly comprising optical transmitter,receiver design and polarization demultiplexing,phase blur detection,symbol decisions DSP algorithms design.The simulation results show that PS-(D)QPSK obtained approximately 2dB OSNR tolerance promotion at the same symbol rate(30Gbaud)and 0.7dB OSNR tolerance promotion at the same effective bit rate(120Gbps)compared with PM-(D)QPSK;And in offline experiments under 32Gbaud symbol rate,PS-(D)QPSK received about 2dB OSNR tolerance improve compared with PM-(D)QPSK.2.For the modulation formats in elastic optical networks which are required to adjust spectral efficiency and transmission reach required in fine-grain,an elastic multi-dimensional modulation method based on multi-symbol parity check is proposed.This method can be combined with a variety of Gray mapping modulation formats such as Gray mapping polarization multiplexing-Quadrature Phase Shift Keying(PM-QPSK),polarization multiplexing-16 order quadrature amplitude modulation(PM-16QAM),the spectral efficiency and the transmission reach can be adjusted by changing the number of related symbols.The simulation results under 32Gbaud symbol rate show that,multi-symbol check PM-QPSK system(PM-kSC-QPSK)can effectively achieve fine-grained spectral efficiency adjustment of 1.5?2 bit/symbol/polarization and transmission distance adjustment of 8000?12600 km,multi-symbol check PM-16QAM system(PM-kSC-16QAM)can effectively achieve fine-grained system spectral efficiency adjustment of 3.5?4 bit/symbol/polarization and transmission distance adjustment of 1750?2600 km.And in the offline experiment under 32Gbaud symbol rate,we verify the fine-grained adjustment of back to back OSNR tolerance for PM-kSC-QPSK and PM-kSC-16QAM formats.3.To meet the needed of experimental research for new mechanisms and new algorithm in the high-speed coherent optical transmission,ultra 100Gbps polarization multiplexing order modulation-coherent optical transmission offline experiment platform is designed and built.The experimental platform supports PM-QPSK,PM-16QAM and other higher order modulation formats,support DSP processing for the sender and the receiver,support up to 32Gbaud modulation symbol rate.And successfully carried out experiments for 25Gbaud(100Gbps)-PM-QPSK and 20Gbaud(160Gbps)-PM-16QAM back to back system.4.In order to reduce the OSNR requirement when maintaining the system spectrum efficiency,increase the transmission distance,an ultra 100Gbps coherent optical communication multilevel coded modulation scheme is designed.The scheme combines high performance LDPC code and PM-16QAM modulation format to carry out the multilevel coded modulation,each component LDPC code rate is designed with the channel capacity rule,and the multi-stage decoding are used as the decoding method.Simulation results show that,the multilevel coded modulation system based on LDPC and PM-16QAM has about 6dB coding gain at BER of 10-4.