Study Of Transmission Performance Of High Spectral Efficiency Optical Modulation Signal

With the rapid growth of the data business of the global broadband, data informationtransfer amount is increased sharply. The carrying capacity of the existing optical fibercommunication systems increasingly inadequate, which promoted the next generation ofhigh performance, large capacity optical communication system’s JvJlopmJnt. It has ahigh-speed, large-capacity and long-distance transmission characteristics, but badlyaffected by transmission impairments such as tight-filtering, chromatic dispersion,nonlinear effect, which limits the transmission performance of the systems severely.Modulation format is one of the key technology of the systems, but the traditionallow-level modulation formats are not performance well to resist the transmissionimpairments, also with low transmission efficiency, can not meet the requirements of thenext-generation of optical fiber communication system. It is particularly important toresearch new types of modulation format for the next-generration system.In this work, the transmission impair factors in the optical fiber communicationsystem and the basic cause of those impairments were analyzed. Characteristics andapplications are given to several low order modulation formats, and the basiccharacteristics of QPSK and16QAM are introduced. To investigate the dispersion,nonlinear effect and tight-filtering effect, the corresponding simulation systems were built.Using those simulation systems, we investigated the tight-filtering effects of the QPSKand16QAM transmission systems, the optimal receive bandwidths were found; then thechromatic dispersion effects of the NRZ-DPSK, RZ-DQPSK, NRZ-DQPSK and16QAMtransmission systems were investigated, it shows that the narrower of the sNLnal’sspectrum, the stronger anti-dispersive. Also, the nonlinear effects of several types ofNRZ-DQPSK and16QAM transmission systems were investigated, the results show thatthe transmission performance degraded by the nonlinear effects between the polarizationstates and XPM.The time-domain and frequency-domain dispersion compensation characteristicswere also analysed in this work. For the frequency-domain compensation (FDE), thiswork gives the basic principles and the corresponding algorithm descriptions, especiallythe OFDE. Finally, we investigate the dispersion compensation performance of OFDEthrough the QPSK and16QAM simulation system, the results show that OFDE cancompensate the dispersion without OSNR penalty when the valid data length of the FFToperation meets the certain requirement.