The Study Of Chromatic Dispersion Monitoring Method In High-Speed Coherent Optical Communication Systems

DWDM optical network develop for the direction of the dynamic network,and the dynamic network have a light characteristics that transmission path of the light signal continuously changes with time varying when optical signal have a long distances transmission in the optical fiber.It is because fiber have some inevitable defects in the manufacturing process and the signal transmission intermediate nodes caused some quality impact. There are some typical physical damage for example OSNR, material dispersion, polarization mode dispersion, nonlinear effects, and so on. In order to control a signal transmission quality in real-time, It is necessary to implement more stringent control and management of network routing, and optical network performance monitoring technology (OPM) came into being that can solve various problems in the all-optical networks. OPM technology is a processing light channel portion of optical detection signal techniques for estimating the performance of an optical channel. Chromatic dispersion is one of the most basic parameters of the optical signal, and CD has a very important significance in the optical signal to measure optical network performance, and it is essential in the optical performance monitoring in the network. In the optical network configuration, optimization, and early warning,CD can’t be separated on reference parameters. So it has a profound impact that monitoring the CD effectively and accurately in a dynamic intelligent optical networks. Therefore, in the optical communication transmission, it is often an important criterion for judging the quality of the optical transmission as.In this paper,the main work is as follows based on the chromatic dispersion monitoring,1. We improved the method for chromatic dispersion estimation technique by using auto-correlation of signal power waveform (ACSPW) for coherent systems, and Expand the scope of this monitoring method,and This method is focused on the relative performance of the link. The autocorrelation function of Coherent electric signal after reception contain the information that is accumulated in chromatic dispersion link, extracting autocorrelation function in dispersion information, to achieve the purpose of monitoring and expanding the scope of monitoring. Theoretical formula are derived and analyzed proved that the method is not amplified spontaneous emission noise, pulse shape and polarization mode dispersion effects, and thus building a Matlab simulation platform in order to further the method is validated. Simulation results show that this method will essentially mean error monitoring results for127ps/nm, and achieve the design requirements.2. Establish coherent reception simulation system to verify dynamic monitoring and compensation technique by using peak to average power ratio (PAPR) as a feedback, and verify that this method is insensitive for pattern, polarization mode dispersion and polarization dependent loss in the simulation platform. Because the smallest PAPR typically corresponds to the CD that results in the best performance, and PAPR is used as feedback signal. We search PAPR minimum through direct search and two search algorithms and extracts the tap coefficients of the filter to monitoring CD. CD compensation value is the accumulated value in the link. The average errors of two methods to monitor CD are312,226ps/nm. Therefore two search algorithm has lower complexity, and higher sensitivity.3. Chromatic dispersion (CD) dynamic monitoring and compensation technique by using peak to average power ratio (PAPR) to as a feedback is used in Nyquist coherent communication system. Because the smallest PAPR typically corresponds to the CD that results in the best performance, and PAPR is used as feedback signal. We build Nyquist coherent reception system and proposed the segmented compensation methods that can stepwise narrow search scope and reduce the step size to make a more accurate monitoring and compensation. The average errors of monitoring and compensating CD are216ps/nm. Therefore this method has low complexity, high sensitivity and insensitive for PMD.