The Reseach Of OSNR Monitoring Techniques For PDM Optical Communication System

In today’s high speed wavelength-division multiplexed (WDM) systems, the bitrateof single channel has begun to40-Gbit/s and100-Gbit/s evolution. The forth comingIEEE100Gb/s standard,802.3ba, provides greater bandwidth, higher data rates, and amixture of advanced modulation formats. The polarization division multiplexing (PDM)technique can effectively double the spectrum efficiency and received extensiveattention of the industry. In PDM optical communication systems, as one importantmeans of network fault location and performance monitoring, the optical performancemonitoring (OPM) technique makes sure that rapid growth of high-performance opticalnetworks can be enabled. The optical signal-to-noise ratio (OSNR) is one of the mostuseful parameters for estimating the quality of a signal directly in the optical layer.During the past decade, many researchers have attempted to develop a techniquecapable of monitoring the true value of OSNR (i.e., in-band OSNR). For this purpose, itis necessary to differentiate and detect small noise components hidden behind the largesignal. This makes our monitoring work more difficult.In this paper we propose various OSNR monitoring techniques for PDM-QPSKand PDM-16QAM transmission system. Meanwhile, to obtain the accurate OSNR valuein the progress of OSNR monitoring，we study some correlated channel estimation andcompensation technology such as chromatic dispersion (CD) compensation, phasecompensation and polarization de-multiplexing (PDM) in polarization divisionmultiplexing system. The main contents are as follows:1. Introduce various OSNR monitoring techniques based on the principles ofdifferent optical characteristics of the signal and noises. Discuss the development trendof OSNR monitoring technology.2. Introduce the high-speed polarization division multiplexing opticalcommunication system with coherent detection and its’ mathematical model.3. The frequently-used digital signal processors (DSP) technologies in coherentoptical communication system have been discussed and analysed, such as CDcompensation, phase compensation, polarization de-multiplexing (PDM). We mainly research the PDM technology for multi-format modulation signals, for example Stokesspace based polarization demultiplexing (SS-PDM). Based on the above-mentionedDSP technologies and the conventional amplitude and phase histograms analysistechniques we propose some signal-to-noise ratio (SNR) monitoring schemes for OSNRmonitoring.4. A variety of OSNR monitoring schemes for multi-format modulation signalssuch as PDM-QPSK signal and PDM-16QAM in polarization division multiplexingsystem have been designed.5. The DSP technologies for channel estimation and compensation, polarizationde-multiplexing and OSNR monitoring in coherent optical communication are allverified by simulation in virtual optical instruments (VPI) and matrix laboratory(MATLAB) co-simulation platform. The simulation results show that polarizationdemultiplexing by SS-PDM for PDM-multi-format modulation signals is successful,and the OSNR monitoring schemes are feasibility.