Study On Resilient Optical Network Architectures Under Metro-access Integrated Situation

With the emergence of many new applications,such as Ultra-HD video,smart home,cloud computing,virtual reality,and so on,network traffic is exploding.In the August 2013,a “Broadband China” strategy regarding broadband networks as a national strategic public infrastructure is formally proposed in China.However,the traditional three-layer network architecture,including core layer,metro layer,and access layer,is too redundant to meet the requirements of future optical networks.Currently,researchers widely believe that it is the inevitable development trend of telecommunication network to integrate the metro layer and the access layer into the “metro-access layer”.The integration of metro layer and access layer can effectively break the bottleneck of requiring a lot of photoelectric conversion between traditional access networks and metropolitan area networks.Furthermore,the integration enable telecom operators to greatly reduce the cost of network construction and operation and maintenance.The utilization rate of network resources can also be improved.The realization of super-large bandwidth has aroused people's worry on another problem.If the network fails,massive data will be losed.At the user level,many realtime businesses,such as telemedicine,cannot tolerate long-time network failures.Therefore,it is of great significance to research a highly reliable network architecture with self-healing ability.On the other hand,due to the migration flow of subscribers and the demolition and reconstruction of community,the scalability of the network is another important issue that need to be considered by telecom operators.This involves the scale of users and coverage that the network can support.The reliability and scalability of the network can be collectively referred to as the resiliency of network.In addition,in traditional access networks,direct communication among optical network units(ONUs)can not be supported.The communication information must be transmitted to the central office(CO),and then,redirected to the destined ONU.This will cause transmission delay,congestion at CO,and occupation of bandwidth in both downstream and upstream channels.In this thesis,the resilient optical network architectures under metro-access integrated situation are researched.Several resilient optical network architectures with novel functions and characteristics are proposed.The main research contents of this thesis are as follows:1)A resilient intersection-ring architecture for metro-access networks is proposed.Based on the intersection-ring topology,the network architecture can not only realize online expansion via exploiting expanding modules,but also carry out mutual protection between intersection nodes without extra cost.Because of the dual-fiber ring structure,the network can resist multiple fiber faults simultaneously.Owing to transmission of the downstream and upstream signals in different fibers along the same direction,the influence of Rayleigh backscattering(RB)noise can be mitigated in both normal work mode and protection mode.The results of performance comparisons show that the proposed architecture performs better than the previous architectures in terms of scalability,reliability,and mitigation of the influence of RB.2)By using conventional optical passive components,a wavelength-routing module(WRM)with M ports is designed.The symmetry and passivity of the WRM makes it be easily integrated and very cheap in practice.Then,a novel architecture of hybrid passive optical network(PON)is proposed by introducing a WRM.In this architecture,ONUs are connected into two types of structures,i.e.,ring network and grid network.In practical engineering application,telecom operators can select different ONU-interconnected manners according to different service characteristics.Depending on WRMs,the ring networks and grid networks can realize online access.With the help of optical switches and interconnecting fibers,full-fiber-fault protection and dynamic bandwidth allocation can be realized in the network.Furthermore,by injecting signals into left and right branches in access ring simultaneously,the transmission delay can be decreased.3)A grid architecture supporting intracommunication and intercommunication for a metro-access network is proposed.By employing an arrayed waveguide grating(AWG)and coarse wavelength division multiplexer in a remote node,the network can not only realize intracommunication between ONUs within one WDM-PON but also support intercommunication between ONUs belonging to different WDMPONs.As a result of allocating one specific wavelength to an ONU to transmit direct communication signals and utilizing the periodic assignment property of an AWG,discretionary peer-to-peer direct communication between ONUs can be achieved.In addition,because the interconnecting manner among ONUs adopts grid,both the scalability and the reliability of the network can be improved dramatically.The results of the performance comparisons show that the proposed architecture performs better than the previous architectures in terms of grid topology and supporting direct communication between ONUs.