Research On Key Techniques In High Speed And High-order Coherent Optical Communication Systems

With the rapid development of broadband information services,people's demand for information is growing exponentially.The traditional optical communication system based on intensity modulation/direct detection can no longer meet people's daily communication needs.In order to achieve the goal of information transmission with larger capacity,higher speed and longer distance,the high-speed coherent optical communication systems based on high-order modulation,coherence detection and digital signal processing technology came into being.Compared with the traditional optical communication systems,the coherent optical communication system effectively improves the spectrum utilization of the system.In the receiver,the impairments of the signal in the transmission link is compensated and recovered by digital signal processing(DSP)technology.The signal processing from the optical domain to the electrical domain can improve the performance of the system and reduce the communication cost.This paper mainly studies and analyzes the generation of high-order modulation for signals and the compensation of signal impairments during transmission by DSP.The main research works of this paper are as follows:(1)The generation method of DP-QPSK,DP-16 QAM and DP-64 QAM modulation format signals are studied,224Gbit/s DP-QPSK,336Gbit/s,448Gbit/s DP-16 QAM and 120Gbit/s DP-64 QAM coherent optical communication simulation platform are set up.(2)The transmission link damage and the formation principle of the damage are studied,and the common coherent detection methods and the coherent detection principle are analyzed.The effects of different damage on the coherent optical communication system based on different modulation format are analyzed by simulation.(3)The relevant algorithm is used to compensate and recover the signal damage.This paper mainly studies dispersion compensation,polarization demultiplexing,adaptive equalization,nonlinear compensation,carrier frequency offset estimation and carrier phase estimation.The compensation principle and compensation effect of the corresponding algorithm are analyzed and discussed.(4)A novel DP-16 QAM signal receiver is proposed.The stability of the receiver is improved and the error rate of the received signal is reduced by using the Kerr nonlinear effect in the normal dispersion fiber.An 8-channel 112Gbit/s DP-16 QAM high-speed coherent optical dense wavelength division multiplexing simulation system is built.The proposed scheme is compared with the traditional scheme for different transmission distance,launch power and laser linewidth.The research shows that the new receiver can effectively reduce the bit error rate of the 112Gbit/s DP-16 QAM DWDM(dense wavelength division multiplexing)system.