Research On Key Technologies Of Faster-Than-Nyquist Optical Transmission System

With the continuous vigorous development of Internet industry and information technology and the vigorous promotion of the government,the demand for network bandwidth in today’s society is growing rapidly.According to Cisco’s prediction,from 2017 to 2022,the global IP data traffic has reached a compound growth rate of 26%compared with the previous period.In the face of such a large traffic demand,the required information transmission bandwidth utilization will increase significantly.As a vital core part of the modern communication industry,optical fiber communication network supports the business needs and technological innovation of the Internet and wireless mobile network.The acceleration network architecture has undergone profound changes,and optical fiber communication needs to continuously expand and improve the transmission capacity to meet the expanding traffic demand.FTN symbol rate transmission system can transmit more than 30%more data symbols than Nyquist transmission system under the conditions of the same bandwidth,the same signal energy and the same bit error rate performance.Therefore,in the communication field with increasingly tight spectrum resources,FTN,as a method that can effectively improve spectrum efficiency,has attracted extensive attention.Based on improving the overall capacity of single-mode optical fiber communication system and improving the spectral efficiency of the system,this paper studies the Faster-than-Nyquist transmission technology in optical fiber transmission system,studies the impact of inter symbol interference introduced by multi binary filter in WDM system on optical fiber transmission system,and puts forward a scheme of adaptive binary detection to alleviate FTN inter symbol interference.The effects of probabilistic shaping and geometric shaping on the spectral efficiency of FTN transmission system are analyzed.Finally,FTN-WDM based on multi-band optical fiber transmission system is proposed,which can expand the capacity of transmission channel by expanding the band while improving the spectral efficiency.The main work of this paper is as follows:(1)Research on adaptive detection technology in FTN-WDM systemAiming at the problem that the bit error performance of FTN system with inter symbol interference in WDM system decreases,an adaptive duobinary detection technology combined with MLSE detection is proposed.Using this technology,the effects of duobinary shaping and triple-binary shaping on the inter symbol interference in FTN-WDM system are studied,and the effects of transmission interval in WDM system on the bit error rate performance of QPSK and 16QAM modulated FTN system are explored.The results show that,The multi-binary shaping effectively suppresses the ICI in the wavelength division multiplexing system.The duobinary shaping in QPSK modulation format effectively improves the SE of the system by 1.2 times,and the required SNR is moderately increased by 1.5dB.(2)Research on constellation forming technology in FTN optical transmission systemAiming at the problem of further improving the reliability of FTN system,a forming method of Faster-than-Nyquist transmission system based on constellation forming is proposed in this paper.The effects of RRC roll off coefficient and constellation formation mode on the performance of FTN transmission system are simulated and observed.The results show that on the premise of achieving the same spectral efficiency,the performance of FTN transmission system with probability shaping has a performance gain of 6dB compared with FTN-16QAM transmission system,and FTN-8+8APSK has a gain of 2.2db compared with FTN16QAM.The average mutual information analysis shows that constellation shaping effectively improves the reliability of FTN transmission system,and the promotion effect of probability shaping is better.(3)Research on multi-band extension technology in FTN optical transmission systemAming at resolving the limited broadband range of the current optical fiber transmission system,this paper proposes to gradually expand the band range of UWB optical wavelength division multiplexing technology from the most widely used C or L band to form a multi-band optical fiber transmission system.Combined with the adaptive modulation format,FTN technology is used to compress the signal frequency interval and the receiver uses the method of adaptive binary detection to improve the reliability of the system.The experimental results show that the introduction of FTN technology can improve the spectral efficiency of Oband by 20%,E-band by 2.75%and C-band by 1.6%.