A Research On FTN Technology For Improving Transmission Rate In High Speed Coherent Optical Communication

With the explosive growth and exponential growth of various ultra-large data services in the Internet era,the demand for high-speed,ultra-large capacity and transmission quality is also growing rapidly.The 100 G and 400 G high-speed coherent optical communication systems are characterized by high integration and good transmission quality.At present,there are a large number of theoretical research and commercialization examples for high-speed coherent optical communication systems at home and abroad,and the research results are relatively mature.However,with the urgent increase in the demand for optical communication bandwidth resources,people have higher and higher requirements for frequency band transmission efficiency.Faster Than Nyquist(FTN)technology,as a good technology to effectively improve the transmission efficiency of the frequency band,has recently attracted people's attention.However,in the specific implementation process of the FTN technology,since the transmitting end of the system artificially introduces interference between certain signals,complex and appropriate techniques are needed at the receiving end of the system for signal recovery.Since the FTN technology itself will cause interference between signals,the FTN technology will bring certain penalty to the error performance of the system.In order to ensure the error performance of a certain communication system,the system receiving end often adopts some complicated measures to compensate the signal interference,which will increase the complexity of the entire FTN system.Therefore,the main factors limiting the development of the Faster Than Nyquist technology are the complexity of the system and the error performance of the system.This thesis first analyzes and studies the traditional time-frequency domain FTN technology.For the traditional time domain FTN technology,the receiver of this thesis uses the commonly used LMS equalizer to compensate ISI.In the traditional frequency domain FTN technology,the receiver of this thesis uses the butterfly equalizer of the pipeline model for signal recovery.However,for the traditional time-frequency domain FTN technology,the system transmission efficiency is more concerned with the system error performance.Therefore,this thesis focuses on the influence of the system transmission efficiency of the traditional time-frequency domain FTN technology on the system error performance.The simulation results show that the error performance of the system will be worse with the increase of transmission efficiency in both time domain and frequency domain FTN technology,and the trend of this variation is faster and more obvious when the bit transmission efficiency increases.Therefore,in view of these problems,this thesis first compares the traditional time-frequency domain FTN technology under the same transmission efficiency,and then compares the Time Division Hybrid Modulation(TDHM)technology with the same bit transmission efficiency with the traditional time-frequency domain FTN technology.The simulation results show that under the same transmission efficiency,the traditional time domain and frequency domain FTN technology has almost the same error performance,that is,the error performance of the traditional time-frequency domain FTN technology is almost consistent with the decline of transmission efficiency.The traditional time-frequency domain FTN technology has much worse error performance than TDHM technology under the same bit transmission efficiency.Based on the research results of traditional time-frequency domain FTN technology,this thesis finds the shortcomings of traditional time-frequency domain FTN technology in terms of bit error performance and system complexity.Based on this,this thesis innovatively proposes a new block FTN technology.This thesis first introduces and analyzes the aspect of block FTN technology using digital combination.For the problem of decision complexity of block FTN technology,this thesis proposes a simplified decision method.In order to verify the advantages and feasibility of this block FTN technology,this thesis firstly performs simulation verification under a simple AWGN channel.In the simulation process,the TDHM technology and the block FTN technology are compared and simulated under the same bit transmission efficiency.Advantages in terms of code performance.Finally,this kind of block FTN technology in coherent optical communication system is studied,and the performance of all aspects of the system is analyzed by long-distance transmission.