Study On Key Technologies Of Optical Performance Monitoring In High-Speed Optical Transmission System

With the rapid development of data services such as cloud computing,the internet of things,artificial intelligence,and 5G mobile communications,the global internet traffic demand has shown an exponential growth trend.This has brought huge challenges to the optical fiber communication network,which is the cornerstone of information transmission,and forced it to towards a high speed,long distance,low cost and reconfigurable direction.However,in the face of complex network structure and scarce spectrum resources in the future,the traditional solutions to deal with link damage by increasing redundancy or by prior information are no longer applicable.Therefore,in order to reduce the network operating cost,maximize the utilization of resources and ensure the optimal operation of high-speed optical transmission network,continuous optical performance monitoring(OPM)is essential.As the key parameters of optical performance monitoring,modulation format(MF),optical signal-to-noise ratio(OSNR)and residual chromatic dispersion(RCD)are the focus of research.This thesis focuses on the key technologies of optical performance monitoring in high-speed optical transmission systems,and the main research contents are summarized as follows:1.By using a modified particle swarm optimization(M-PSO)design,a novel and blind modulation format identification(MFI)scheme was proposed for elastic optical networks(EONs)in this study.Compared with the traditional PSO algorithm,the sight of each particle in M-PSO algorithm was strictly restricted to perform search of local extremum points(LEPs)on density distribution histograms(DDHs).In the experiment,the distributions of LEPs on DDHs depended on signals' modulation formats,and then were regarded as the key identification metric.The proposed MFI scheme did not need prior information of OSNR in the identification processes,and showed a natural resistance to frequency offset and line width.The feasibility of the proposed scheme was verified by 28 GBaud polarization division multiplexing(PDM)-BPSK/QPSK/8QAM/16 QAM transmission system,where the simulation results showed that the lowest OSNRs required to achieve 100% identification rate were all lower than their corresponding 7% forward error correction(FEC)thresholds(BER=3.8e-3).Furthermore,the tolerance of the residual chromatic dispersion(CD),differential group delay(DGD)and nonlinear effect were also verified under the simulation conditions.The study results manifest that the proposed MFI scheme showed interesting robustness to both linear and nonlinear impairments.Moreover,we also demonstrated a relatively simpler calculation complexity under the proposed MFI scheme.2.We propose a multi-parameter optical performance monitoring scheme of Stokes Vector Direct Detection(SVDD)optical transmission system based on trajectory information,which can realize MFI,OSNR monitoring and RCD estimation at the same time.It is well known that the distribution of cluster is diverse for different modulation format signal disturbed by variant impairment.To be precise,the number and divergence of clusters is various.The trajectory consisted of line drawing between adjacent symbols not only can accurately exhibits the above diversity in space dimensionality,but also records jump pattern among symbols in time dimensionality.Therefore,we attempt to quantify the trajectory of signal to excavate subtle information contained therein in order to operate OPM.By utilizing the VPI transmission Makers 9.3 and Matlab software,we verified the feasibility of the proposed scheme.For the joint MFI and OSNR monitoring in the SVDD system based on trajectory information,within the selected reasonable OSNR range,SVDD-BPSK,SVDD-QPSK,SVDD-8QAM,SVDD-16 QAM,SVDD-32 QAM and SVDD-64 QAM can be 100% identified.For the multi-parameter optical performance monitoring in the SVDD system based on trajectory information,the proposed scheme can be 100% identified even if the RCD reaches 160 ps/nm within the corresponding OSNR range,and the average mean absolute error(MAE)of OSNR monitoring and RCD estimation are 1.08 d B and 3.22 ps/nm,respectively.Furthermore,we also demonstrated the robustness for baud rate and a relatively simpler calculation complexity about the proposed OPM scheme.