Study On Broadband Passive Optical Network With Large Capacity

In recent years,China have witnessed rapid development of tecnology and science,with varieties of high-end network applications and techniques (e.g.,high-definition video,virtual reality (VR) and internet of things (IoT)) significantly enriching our life experience and basically interconnecting everything around us.Cisco whitepaper predicts that within the next five years,the number of devices in IP network will grow rapidly to exceed more than three times the population in the planet.It is estimated that in the end of October 2019,the number of FTTH/O (fiber to the home/office) subscriber has reached 416 million,accounting for 92%of the total population using fixed broadband services.In addition,the number of fixed broadband subscribers with more than 100 Mbps access rate to the Internet has reached 370 million,up to 81.8% of the total number.Broadband passive optical network,regarded as the bridge connecting users and backbone network,need to provide larger system capacity,higher transmission bandwidth and signal quality,as well as more flexible and effective resource scheduling algorithm with lower latency,in a bid to satisfy the ever-growing number of network users and varieties of network services.In addition,as the scale of network contine to expands,the problem of high enery consumption in optical access network must be solved.Bringing the performance of large capacity,high energy-saving and low-latency in broadband passive optical network will be the key technology,which has been studied extensive worldwide.Constellation shaping,considered as digital signal processing technique,capable of enlarging system capacity and improving signal quality,has received considerable investigation in optical access network.And software defiend networking can function as a novel networking approach to centrally manage optical access network to implement effective and on-demand resource scheduling,thus providing high energy-saving efficiency for the complicated access network architecture.Moreover,since the diversification of users' demand and fine granularity of network services is a key element in the effective network operation,it is imperative to study the dynamic bandwidth allocation algorithm,so as to realize the optimization of network resource scheduling and refrain from frequent congestion and packet loss,as well as high packet delay.Based on the study of broadband passive optical network,this dissertation focuses on the transmission capacity improvement scheme for varities of multiplexing PON.The combination of geometrical shaping and probabilistic shaping is employed to improve the signal quality (e.g.,bit error rate performance and optical signal-to-noise ratio (OSNR)) and effectively boost the system transmission capacity.The dissertation also applies the principle of software defined networking (SDN) to the control plane in the optical access network to achieve the centralized management and flexible wavelength scheduling,thus reducing the energy consumption of the system.In addition,by taking the application scenario and specific traffic characteristic into full consideration,the dissertation achieves flexible network resource scheduling to effectively and dynamically manage the bandwidth allocation with different priorities in a real-time manner,so as to accomplish the optimization of the network utilization,significantly reduce the average packet delay and improve the data throughput in the optical access network.The main work and innovations in this dissertation are presented as follows:1.PS-WDM-PON transmission scheme with enlarged capacity based on symbol-level labeling and rhombus-shaped modulationBased on the study of WDM-PON architecture and constellation shaping technique,a probabilistic shaping WDM-PON transmission scheme employing symbol-level labeling and rhombus-shaped modulation is proposed.By means of increasing the transmitting probability of the signal points with lower power,the energy concentration of the constellation can be greatly enhanced,so as to relieve the requirement for the signal emitting power and improve the system bit error rate (BER)performance.The experimental setup of a 20 km PON transmission indicates that in the threshold of 1*10-3 BER,the proposed 16-9 CAP outperforms the conventional 16-CAP by 2 dB gain in receiver sensitivity,which effectively improves the system transmission capacity and signal quality.2.IM/DD OFDM-PON transmission scheme with enlarged capacity based on constellation structure optimizationBased on the study of OFDM optical access network,a IM/DD transmission scheme based on constellation structure optimization is proposed in OFDM-PON.By geometrical design for the signal points in the different rings of the constellation,signal points can be converged more inwardly to obtain the maximization of the constellation figure of merit(CFM).In the meantime,the optimization of the probability distribution of the signal points in the constellation can further reduce the average signal power.Moreover,by setting up the system platform and applying DSP technique,the PON transmission experiment under different symbol rates and entropies is carried out.Experimental results indicate that compared with the traditional modulation schemes,1.5 dB gain in receiver sensitivity can be achieved and better BER performance can be observed,thus relieving the burden of high emitting power in the transmitter.The advantages of low power consumption,economical implementation and low computation complexity enable the proposed scheme to achieve better signal transmission quality in various application scenarios in a low-cost manner.3.SD-TWDM-PON transmission scheme with high energy-saving efficiencyBased on the basic principle and application of SDN,a high energy-saving SD-TWDM-PON architecture is proposed.By dynamically and adaptively provisioning and scheduling varieties of resources in PON,streamlined operation and management can be realized in optical line terminal (OLT) and optical network unit (ONU).According to the network load,the tradeoff among energy-saving,link rate,time slot allocation and QoS performance can be considered and arbitrated in a dynamic and real-time manner,so as to achieve sustainable,stable and efficient operation in the PON.Experimental results indicate about 75% of the transceiver energy can be saved in the OLT while guaranteeing the QoS requirement.Moreover,by appropriate configuration in the transceiver and link rate,efficient energy-saving can be achieved in SD-TWDM-PON while maintaining the network performance in presence of average packet delay,jitter and throughput.4.Bandwidth allocation algorithm in TWDM-PON system with low latencyTaking the effective network performance of PON into full consideration,a dynamic bandwidth allocation algorithm based on QoS is proposed.By optimizing the bandwidth allocation for high priority services and applying polling and reservation mechanism,16% network utilization improvement and 35% average packet delay decreases can be obtained in high network load.This dissertation also proposes an adaptive resource scheduling scheme based on enhanced random early detection,which flexibly adjusts the threshold for the forwarding queue,in a bid to reduce the congestion rare for the delay-sensitive services in a dynamic and real-time manner.In addition,the fair and effective bandwidth allocation can be guaranteed for bursty traffic.Network simulation results shows that the proposed scheme outperforms the traditional network by 12% throughput increases and 33% packet delay,suggesting enormous superiority in satisfying the urgent requirement of network resource and performance in optical access network.