Research On Optical Interconnection Mechanism In Cloud Datacenter Based On Coherent Detection

With the development of many emerging technologies,such as artificial intelligence,Internet of things and big data,industrial society is about to enter the era of the fourth industrial technology revolution.Many technologies have spawned massive amounts of data.In order to transmit and process the exponential growth of data,large-scale datacenters,represented by cloud datacenters,are popping up all over the world.Cloud datacenters with a set of flexible and fast data exchange and transmission management system can respond to the needs of multiple business quickly and accurately and achieve high utilization efficiency of resources.In terms of physical layer transmission in cloud data center,aiming at different transmission scenarios,this paper designs a coherent optical interconnection system based on high-order modulation,multi-dimensional multiplexing,coherent detection and digital signal processing technology.Based on the optical interconnection inside the cloud datacenter,a low cost and large capacity coherent optical communication system with DP-16QAM,heterodyne detection and digital signal processing is proposed.At the same time,the millimeter-wave signal generated by heterodyne detection is used to cover the local cloud datacenter directly in order to realize the signal transmission of wire and wireless.A set of digital signal processing algorithms for short distance transmission is studied,including the dynamic equalizer of polarization demultiplexing based on butterfly filter,estimation and compensation of carrier frequency and phase.The transmission performance of coherent optical interconnection system under different optical devices is analyzed by simulation,including different linewidth of lase(100KHZ,1MHZ and 10MHZ),different response bandwidth of photoelectric detector(35GHZ,40GHZ and 60GHZ).According to the measure of devices and algorithm complexity,the scheme choose the optimum solution to meet the requirement of system transmission bit error rate with the low cost and large capacity interconnected scene demand in intra-datacenter.An optical orthogonal time-division multiplexing system based on QPSK,Nyquist pulse shaping,homodyne detection and improved digital signal processing was designed for inter-datacenter optical interconnection.The periodic Nyquist pulse with a period of 0.1ns and a half-wave bandwidth of 0.011ns is generated by the cascade Mach-zehnder modulators,which is used as the optical carrier of the time-division multiplexing system.The training sequences,inserted into the data in transmitter,are used to lock the phase and impairment compensation.First,the algorithm of sliding window based on training sequences is used to realize the function of phase-locked loop.At the same time,the training sequence evaluates the channel quality and compensates the residual physical damage caused by the signal transmission process.After the transmission of single channel 10GBaud signals with 8-channel Nyquist optical pulse time-division multiplexing channel,the bit error rate of the system is lower than the decision threshold of forward error correction code beyond the transmission distance of 150km.In terms of cloud datacenter network structure,this paper designs a 3D network model with low fragmentation which combines the physical layer Nyquist time-division multiplexing system.Combined with physical layer virtualization technology and software-defined network technology,Mininet experiment platform and Ryu controller were used to build the SDN environment.Meanwhile,the leaf-spine network structure of the cloud datacenter is simulated and the network traffic inside the cloud datacenter is test.