Research On High-order Signal Modulation Technology And Transmission Method In High-speed Optical Communication System

With the rapid development of Internet and mobile internet,the demand for information is expanding rapidly.Internet traffic has been growing explosively.More and more video streams,cloud computing,social media and mobile data transmission have put forward higher requirements on the network scale,rate,capacity and distance of optical fiber communication system,which is moving towards ultra-high speed,ultra-long distance,ultra-large capacity and ultra-high frequency spectral efficiency development.The modulation format transits from the traditional sxwitch phase shift keying(OOK)to a higher order modulation format.In order to meet the increasing demand for communication capacity,this paper studies the advanced modulation formats used in optical communication.The research contributions of this thesis are as follows:1)A dual-polarization high-order modulation format signal generation scheme is designed.The effects of transmission power,transmission distance and optical signal-to-noise ratio on the transmission performance of DP-QPSK,DP-16QAM and DP-32QAM signals are simulated and analyzed.2)Different type of constellation diagrams are analyzed,i.e.circle,square and 2A8P are used for the depth analysis of OSNR and BER relationship of 16QAM.Similarly,cross,rectangle and 4A8P are used for 32QAM.The results show that BER decreases with the increase in the OSNR3)Reduce the effects of polarization mismatch and channel impairments by using polarization demultiplexing,dispersion compensation,frequency and carrier phase estimation at coherent receiver.Moreover,the optimal QoS parameter values such as signal to noise ratio(SNR)for fiber of different lengths,angle of polarizing and optical signal to noise(OSNR)tolerance under such channel impairments are presented.