Research On High Speed Interconnection Of Optical Network In Data Center

In recent years,Internet traffic has increased exponentially,driven by new Internet applications such as streaming video,social networking and cloud computing,which puts forward higher requirements for the size of data center.Data center is based on thousands of high-performance server combinations.With the increasing number of servers,the high bandwidth,low latency and low cost optical interconnection technology between servers has become a research hotspot.Compared to the coherent transmission system,the intensity modulation and direct detection(IM/DD)has the advantages of lower power consumption,more compact module size and lower system.For single channel 100Gb/s short distance communication system,previous research has analyzed many modulation formats,such as pulse amplitude modulation(PAM),carrier free amplitude and phase(CAP)and discrete multitone(DMT).The DMT modulation signal has a higher spectral efficiency and is more resistant to the dispersion of the fiber channel,and is more attractive in the future 400Gb/s communication technology.Using VPIphotonics and MATLAB simulation software,many advanced modulation formats and digital predistortion technology in the data center optical network are studied in this paper.The main work and innovation of this paper are as follows:1,aiming at the selection of modulation formats in intensity modulation direct detection system,three modulation technologies are analyzed and compared in terms of system complexity and transmission performance:PAM,CAP and DMT.The analysis results show the feasibility of DMT modulation technology in 400Gbps optical interconnection system.2,in view of the problem that the DMT modulation parameters can not be changed flexibly in the 8.6 version of the VPIphotonics simulation software,MATLAB and VPIphotonics are jointly simulated to solve the problem.MATLAB realizes the modulation and demodulation of DMT signals,and VPIphotonics realizes the generation,transmission and reception of optical signals.The joint simulation scheme not only takes advantage of the flexibility of MATLAB for data processing,but also makes use of the more real optical link simulation system of VPIphotonics.3,according to the nonlinear analysis of complex system problems,the nonlinear damage and fiber caused by the nonlinear damage signal is divided into device damage caused by two,and the two kinds of nonlinear damage from postprocessing,the simulation process shows that the individual treatment scheme simplifies the complexity of the algorithm.4,aiming at the difficult problem of nonlinear modeling,the behavior modeling method is adopted in this paper.Besides the part of the optical fiber,the model is considered as the black box,and the model parameters are calculated through the input and output data of the black box.Compared with the cascade of multiple nonlinear models,this scheme greatly reduces the complexity of the model parameter calculation.4,aiming at the difficulty of calculating the signal to noise ratio(SNR)parameters of each sub channel in bit power allocation algorithm,the EVM of each sub channel demodulation signal is replaced by SNR.From the result of bit power allocation,we can see that the parameters of EVM as algorithm are easier to get.5,according to the problem of memory polynomial digital predistortion technology,the nonlinear region of MZM modulator is divided into effective area and invalid region,which directly reflects the defect of traditional algorithm,and combines partial transmission sequence PTS with DPD.The results show that the new algorithm is more effective in compensating the nonlinear damage.