Research On Phase Noise Compensation Algorithm In Large Line Width CO-OFDM System

With the rise of Internet plus era,coherent optical orthogonal frequency division multiplexing(CO-OFDM)communication system with its high spectral efficiency,support high-order modulation and good transmission performance advantages,as the future high-speed long-distance optical transmission technology.However,compared with other modulation formats in coherent optical communication,the OFDM symbol is longer and more susceptible to laser phase noise.The phase noise of CO-OFDM system is divided into Common Phase Error(CPE)and Inter-Carrier Interference(ICI)phase noise.The former caused by the rotation of the constellation,for each OFDM symbol frequency data rotation of the same angle,it is called public phase noise;the latter from the sub-carrier interference,causing a serious divergence of the constellation.When CO-OFDM in the access network or metropolitan area network applications,it is inevitable to consider the system cost and bandwidth and other issues.Because liners with linewidths less than 100 kHz are expensive,the ability to significantly increase the system's tolerance for laser linewidth will greatly reduce the cost of the system.In this paper,we mainly study the algorithm of compensating the common phase noise and the inter-carrier interference in the large-line-wide CO-OFDM system.Firstly,an algorithm of no-iterative blind(IFB)CPE noise compensation is proposed and improved.Simple cost function to reduce its computational complexity,and through the simulation results confirmed that the improved IFB algorithm in the effect can be comparable with the previous.Then,a blind ICI noise compensation(CPEC)algorithm is proposed.The algorithm has a good ICI compensation effect under the small line width,but there is a problem of incorrect error in the large line width.In this paper,we propose a(ICI)phase noise compensation A-CPEC algorithm by combining this algorithm with the energy average blind(Avg-BL)algorithm.The A-CPEC algorithm proposed in this paper is simulated by 50 Gbit / s 16 QAM CO-OFDM system.The numerical results show that the bit error rate after phase noise compensation is up to the limit of forward error correction(FEC)in a system with a laser line width of 700 kHz.It shows that the algorithm has a good compensation effect on the large linear laser system,which greatly improves the spectrum utilization rate compared with other algorithms.The algorithm can be applied to the CO-OFDM system in the long-distance access network or metropolitan area network,which reduces the requirement of the laser line width of the system,greatly saves the system cost and is important for the application of the large-line-wide CO-OFDM system significance.