Research On The Performance Of PDM-QAM Optical Transmission System

Optical fiber communication technology has greatly changed people's lives in the past three decades.Although the entire optical communications industry has been affected by the bursting of the Internet bubble in 2000,the demand for communication bandwidth for the Internet has reached an unprecedented level due to the rise of high-definition television,mobile multimedia,big data,cloud computing and social networking in recent years,and promote the optical communications industry flourished again.Researchers pursue high speed optical fiber transmission technology to meet people's information needs.This thesis mainly studied the performance of high speed optical fiber transmission system and analyzed the basic theory of quadrature amplitude modulation and polarization multiplexing.This thesis built 200 Gbit/s,320 Gbit/s,500 Gbit/s 16 QAM and 64 QAM polarization multiplexing optical fiber transmission system model,then studied and optimized the system structure.The main contents of this thesis are as follows:(1)The thesis summarized research progress and development trend of orthogonal amplitude modulation and polarization multiplexing.Introduced the optical modulation technology,mainly the MZ modulator and analyzed the quadrature amplitude modulation technique in detail.Then,introduced the demodulation of quadrature amplitude modulation,including direct demodulation and coherent demodulation,and derived formula for coherent demodulation,analysed them in detail.Introduced the polarization multiplexing technique.First,the thesis explained the polarization of light,and then introduced several methods of representing polarized light,there are Jones matrix method,Stokes vector method,and the polarized light can be represented by points on the Poincare sphere.Then the thesis analyzed the principle of polarization mode dispersion and polarization dependent loss in fiber and its influence on the system.Finally,the thesis introduced two methods of polarization demultiplexing,which are coherent demodulation and direct demodulation,and analyzed the principle of coherent demodulation briefly.Then analysed the principle of direct demodulation and how to achieve it in detail.Direct polarization demultiplexing technology can eliminate the late DSP processing of the signal,greatly simplify the system.(2)Using the above theory and analysis,the thesis built 200 Gbit/s,320 Gbit/s,500Gbit/s 16 QAM polarization multiplexing optical fiber transmission system model through the VPI transmission maker 8.3.The simulation system included the generation of the signal which is the transmitter,the optical fiber transmission link and the signal demodulation which is the optical receiver.Then studied the influence of some parameters of the system on the signal.(3)The thesis built 200 Gbit/s,320 Gbit/s,500 Gbit/s 64 QAM polarization multiplexing optical fiber transmission system model through the VPI transmission maker 8.3.Then studied the influence of some parameters of the system on the signal and optimized the performance of fiber optic transmission systems.