Research On Optical Signal Chromatic Dispersion And OSNR Monitoring Techniques

In order to satisfy the ever increasing demands of data traffic,optical fiber communication systems are now rapidly evolving toward the direction of ultra-high speed,ultra-large capacity,ultra-long distance and dynamic reconfiguration.Under this background,the system tolerance to chromatic dispersion(CD),polarization mode dispersion(PMD),nonlinear effect and noise are decreased rapidly.Furthermore these link impairments may change over time due to the dynamic reconfiguration of the networks.In order to promote these evolutions,optical performance monitoring(OPM)techniques are needed to monitor the quality of optical signals,which enables the adaptive distortion compensation and the intelligent optical network management.Hence,OPM has become one of the key technologies for next generation optical fiber communication networks.The monitoring techniques of the two key quality parameter CD and optical signal to noise ratio(OSNR)are studied in this thesis.First,the significance and performance index of OPM techniques are introduced.Then the research status of the OPM techniques based on direct detection and coherent detection are reviewed.Secondly,the main transmission impairments and the working principle of digital coherent receivers are introduced.Thirdly,we proposed a novel hybrid clock tone based CD monitoring technique based on coherent detection.It has the advantages of low computation complexity,wide monitoring range,high precision,PMD insensitiveness and modulation format transparence.Fourthly,coherent detection based OSNR monitoring techniques are studied.The high order statistical moments based technique is compared with the pilot sequence based one.The influence of residual CD and nonlinear effect on the monitoring accuracy is analyzed.Finally,a novel CD monitoring technique based on ultra-high resolution optical spectrum analysis is proposed with which both the spectrum and CD of optical signals can be measured.Furthermore in-band OSNR monitoring technique based on spectrum analysis is also studied.With these techniques more functions can be realized with the spectrum analysis equipment.