Research On Metro-access Integrated Network And Its Key Techniques

Recently,with the diversity of wired/wireless services and the tremendous increase of terminal users,a large number of data flows are converged and need to be exchanged in metropolitan area network(MAN).The traffic growth rate in MAN is two times larger than that in backbone network.In addition,the traditional metro and access networks have a relatively complicated physical infrastructure,which not only leads to the undesired over-consumptions of the valuable network resources,but also considerably limits the network upgradability.To cope with the ever-increasing network traffic growth,the seamless integrations of the traditional metro and access networks have been a potential trend in optical network evolutions.The dissertation is mainly focused on the investigations of the metro-access integrated networks(MAIN).By utilizing the various access techniques,different signal modulation/detection schemes and various switching technologies,different MAIN architectures are designed with an identical “ring + tree” network topology.The in-depth explorations are undertaken for the reconfigurable optical add/drop multiplexers(ROADMs)required in the MAIN switching nodes.In addition,special attention also is given to exploring the feasibility and approaches of providing the all-optical virtual private network(AOVPN)services for the terminal users in MAIN.A MAIN architecture is designed with the network capability of offering concurrent AOVPN communication services.The innovative contents of this dissertation are summarized and listed below.1.Utilizing the orthogonal frequency division multiplexing(OFDM),orthogonal frequency division multiple access(OFDMA),OFDM band multiplexing,time division multiplexing(TDM)and polarization division multiplexing(PDM),an OFDM MAIN is proposed using polarization multiplexed band interleaving technology.The up-stream and down-stream OFDM sub-band signals are transmitted over different polarizations and are interleaved in frequency domain,thus giving rise to an enhanced network bandwidth efficiency.The hybrid access technologies enhance the network flexibility and scalability.The simple architecture of the ROADMs equipped in network switching nodes and the adoption of the traditional OFDM transceivers in network terminal nodes significantly improve the network upgradability.The theoretical analyses are undertaken to explore the impacts of the phase mismatch between the optical carrier component and the optical signal bands on network performances.The corresponding demodulation processes of the up-/down-stream multi-band signals are respectively discussed in detail.2.Employing the digital filter multiple access(DFMA)and wavelength division multiplexing(WDM),a WDM-DFMA-based MAIN is proposed using intensity-modulation and direct detection schemes(IM-DD).The adoption of the DFMA technique not only simplifies the network bandwidth allocation and enhances the bandwidth efficiency,but also improves the network flexibility,elasticity,adoptability and upgradability.Utilizing the passive optical coupling and intensity modulation,a digital signal processing(DSP)-enabled cost-effective and power-efficient ROADM is proposed,which not only provides flexible and dynamic add/drop operations at wavelength,sub-wavelength and spectrally-overlapped orthogonal sub-band levels,but also has excellent performance robustness against variations in modulation formats,digital filter characteristics,transmission system characteristics/impairments and terminal equipment configurations.The ROADM drop operations at a spectrally overlapped orthogonal sub-band level are experimentally demonstrated utilizing commercially available cost-effictive optical and electrical components.3.A WDM-DFMA-based coherent MAIN is proposed,which not only has large network capacity and network coverage,but also has flexbile network bandwidth allocations and high network elasticity.For coherent DFMA communication systems,utilizing Mach-Zehnder modulator(MZM),two simple but effective ROADM drop operation approaches are proposed analytically and validated numerically,which not only have the similar drop performances and can improve the drop performances by approximately 10 dB,but also considerably enhance the drop operation performance robustness to modulation index variations.In addition,the theoretical analyses and the numerical simulation results indicate that the proposed ROADMs have excellent drop performance robustness against the variations in ROADM-equipped MZM extinction ratios,drop radio frequency signal phase offsets,fiber transmittion impairments and DFMA system-adopted digital filtering schemes.Furthermore,special attention also is given to exploring the pratical digital filtering scheme and the optimum digital filter allocation scheme in WDM-DFMA-based coherent MAIN.4.The VPN communications are explored and classified respectively in single-ring and multi-ring MAINs.A WDM-based MAIN architecture is proposed,which can not only provide the concurrent AOVPN communications,but also support the dynamic establishment and removal of the AOVPN communications.In addition,the scalability of the VPN communications is theoretically analyzed,and the dynamic VPN bandwidth allocation is also discussed in detail.Finally,the impacts of the light source linewidth on network communication performances and the feasibility of establishing AOVPN communications in MAIN are respectively explored utilizing IM-DD-based OFDM systems.