High Spectral Efficiency Optical Signal Processing Technology Based On Extended Kalman Filter

In recent years,the optical signal co-estimation technology based on Kalman filter for optical signal sub-module digital signal processing provide a perfect solution in case of link cost,processing delay and tuning parameters coupling,so the method quickly became the research hotspot.Optical signal co-estimation technique could not only simplify the digital structure but also realize tracking and compensation simultaneous.In this paper,we focus on the methods of collaborative estimation of polarization demultiplexing,carrier phase recovery and frequency offset estimation,and then propose a variety of novel methods.Make full use of numerical simulation and experimental platform,the performance of proposed technology could be verified.In this paper,we firstly proposed a blind and simultaneous polarization and carrier recovery scheme for TDHQ signals.This scheme is based on extended Kalman filtering(EKF)and can track polarization and carrier phase simultaneously.Moreover,format combination knowledge in frame structure is not required.Therefore the scheme can operate in a completely blind manner in both convergence and tracking stage.This feature can simplify the receiver implementation and can provide the flexibility for future dynamic optical network.In the following,the principle of the EKF based on polarization and carrier phase recovery of time-domain hybrid QPSK/16 QAM signals is introduced.The proposed scheme is investigated through numerical simulation regarding the performance dependence on the hybrid format parameters and the system parameters,including power ratio(PR),format ratio(FR),phase noise,residual frequency offset,and polarization rotation.Then,the EKF performance in both 16 QAM and 64 QAM case are investigated in detail by considering the influence of the filter tuning parameter under various system/channel conditions,including laser linewidth,frequency offset,and fiber channel polarization rotation.The configuration strategy are suggested regarding different parameter conditions and the dependence of EKF performance on modulation order are also studied.These results can provide meaningful guidelines to ensure optimized metrology of high order QAM signals under diverse operating conditions.In the study of simultaneous carrier recovery and frequency offset scheme,this paper modifies and models the EKF-based co-estimation technique published by Ankita Jain.Then scheme is modified and applied to the 112 Gb /s PD-16 QAM and PD-QPSK systems without considering the non-linear effect.The maximum frequency offset and phase tracking range are obtained by numerical simulation.Based on the previous work,we proposed and demonstrated experimentally an EKF scheme which can track polarization state,frequency offset and phase noise together.The scheme inherently the advantages of fast polarization state tracking capability,high tolerance against laser linewidth and frequency offset.The simulation and experiments has been carried out to confirm its tracking capability under typical operation conditions.Therefore,it has potential application for performance monitoring for dual-polarization high-order modulation formats with fast time-varying laser frequency drift and polarization state.