Research On The Key Technologies Of Improving The Reliability Of Next Generation Optical Access Network

According to the development direction of next-generation optical access network:higher access bandwidth,farther transmission distance,greater splitting ratio and flexible bandwidth resources allocation,the WDM-OFDMA-PON based on network survivability design can be a good to satisfy these development requirements.PON is the main network structure of fiber access network.In recent years,the development of LR-PON(Long Reach-PON)conforms to the requirements of the next-generation access network for farther transmission distance and the integration of metro-access network.WDM technology provides higher bandwidth.OFDM technology enables more flexible multiple access and finer resource allocation granularity,and flexible spectrum technology realizes the dynamic and flexible allocation of network bandwidth resources.With the integration of access network and metro network and the trend of optical network development based on SDN technology,the advanced modulation format,impairments awareness and compensation,and network survivability of next generation access network become key problems to be solved.Based on the WDM-OFDMA-PON network with flexible spectrum,the author proposed efficient modulation schemes,optical signal transmission impairments awareness and evaluation model,as well as dynamic compensation mechanism by DSP technology.A low-cost optical network fault monitoring scheme in the optical network is also designed,and the comprehensive and in-depth research analysis and the scheme optimization are carried out.The results will provide the theoretical basis and technical support for the optimization of signal transmission in the next generation optical access network.The main work and innovation of this thesis are as follows:(1)The thesis introduces the development optical network and the trend of next-generation PON-based optical access network:the metro-access network integration based on LR-PON,the combination of OFDM technology and PON technology,the combination of SDN technology and PON,and the wide application of DSP Technology in optical access network.On this basis,the author analyzed the key problems for improving reliability in the next generation optical access network.(2)The basic principle and mathematical model of QPSK modulation scheme are introduced,and the working principle of PM-QPSK-ROF system is analyzed.An improved PS-QPSK modulation scheme is proposed.The performance compares between the two modulation formats in terms of constellation,EVM versus power.EVM/BER versus IQ imbalance,and the simulation results confirm that the proposed PS-QPSK modulation format is more resistant to IQ mismatch and XPM than PM-QPSK.(3)The principle and mathematical expression of OFDM modulation format and IFFT/FFT implementation are introduced,and the advantages and disadvantages of two kinds of OFDM systems are analyzed.An improved RZ-QPSK-OFDM modulation scheme is proposed and its principle is studied in detail.The even subcarriers and odd subcarriers are processed by IFFT respectively,and then they are combined to be modulated into optical signals for transmission in the optical fiber.By sub-carrier sub-odd-numbered subcarriers,the subcarriers are processed together and then modulated into optical signals for transmission in optical fiber.In addition,the RZ-OFDM-QPSK,NRZ-and the improved RZ-modulation scheme are compared and analyzed in the ROF system.The simulation results show that the proposed scheme has similar spectrum utilization with the NRZ modulation,and it is 2 times of the parameter for RZ modulation format.Besides high spectrum utilization,the transmission performance is better than the NRZ modulation format.(4)The damage caused by optical signal transmission in the fiber including:chromatic dispersion,polarization mode dispersion,IQ imbalance,phase noise,and nonlinear effects are analyzed in theory.The optimized associated impairments awareness evaluation model using Q factor is shown.The influence of interaction among different impairments,different weight parameters and the network margin is considered.For the main damage,the compensation schemes are studied,and the effectiveness of the compensation mechanisms are verified by simulation.(5)In the aspect of optical network survivability,a joint low-cost monitoring algorithm combining monitoring trail scheme and optical coding scheme is proposed in the mesh and tree network.The link and node on the ring are monitored by optical coding scheme,and other optical links are monitored by m-trail scheme.The simulation results verify the good performance of the monitoring algorithm.In addition,the author optimized some parameters in the heuristic MTA algorithm.which enables less numbers of m-trails and reduces costs.