High Speed Channel Equalization In Coherent Optical Communication System And The Study Of The Phase Estimation

With the rapid development of the broadband information network, thewavelength-division multiplexed(WDM) system with single-wavelength100Gb/s hasbecome the mainstream technology for high-speed optical fiber communication.100Gsystems face more serious technical challenges due to the increased transmission rate. Inaddition to the fiber transmission loss and the chromatic dispersion, the polarizationmode dispersion and the nonlinear effects that have little influence on the low speedsystems are the main factors that could seriously reduce the performance of the100GWDM systems. At the same time, the laser phase noise is another important factor thatwill cause system performance loss because of the PDM-DQPSK modulation schemeused in the100G systems uses the.The main work in this paper is to find ways to compensate for those factorsmentioned in the above through the simulation analysis.Thanks to the development ofelectronic digital signal processing technology, the combination of the channelequalization and the carrier phase estimation in the electric field could both equalize thedispersion and compensate for the laser phase noise with an improved systemperformance. The improvement of performance can be seen in the following aspects:reducing the equalizer step-size, increasing the laser phase noise tolerance, getting morestable error performance and transmitting longer distance. Online dispersioncompensation with some residual dispersion per span followed by the electrical channelequalizer to compensate for the residual dispersion at the receiver side is an effectiveway to reduce the nonlinear effects. With a comprehensive consideration of the OSNRgain, the best equalizer length and the system performance, the optimal ICR is found tobe0.6.