Key Technologies Of Physical Layer In Optical Access Network With Advanced Multi-carrier Modulation

With the growth of high-speed Internet,high-definition TV and real-time entertainment,user data traffic has been exponentially increased,which greatly pushes the demand of bandwidth and latency.To meet the enhanced-mobile-broadband(e MBB),large-scale machine-to-machine communication(MTMC),and ultra-reliable low-latency real-time services(URLLC)challenges in 5G.The future optical access network systems need to be equipped with excellent elasticity bandwidth,so that the network can obtain resource utilization in a high efficiency manner.Providing fast adaptive connection solutions to meet the high speed data transmission and the evolutions of the networks with largely diversified characteristics.The optical access network systems based on multi-carrier modulation have been widely considered as one of the most important candidates for realizing the next generation of access networks,due to their inherent high flexibility,reconfigurability and adaptability.To achieve a smooth evolution from 4G to 5G,in addition to the 5G filter bank multi-carrier(FBMC)signal modulation techniques,the multi-carrier orthogonal frequency-division multiplexing(OFDM),and the digital orthogonal filtering(DOF)-multiplexed OFDM multi-channel technologies provide promising signal modulation candidates for the next generation of optical access networks.Therefore,this dissertation takes the key technologies of physical layer in optical access network with advanced multi-carrier modulations as the research objects.Aiming at different access scenarios,various network architectures based on multi-carrier optical access systems have been designed in this dissertation,and special attentions have been given to the explorations of considerably improving signal transmission rates,transmission system power budgets,transceiver flexibility and fast connectivity for different types of services in optical access network systems.The innovative contents of this dissertation are summarized and listed below:1)In order to improve signal transmission rates.According to the MZM modulation characteristics,the return-to-zero(RZ)and the carrier-suppressed return-to-zero(CSRZ)optical pulse sequences are generated,a low cost and high rate optical transmission system based on optical time and polarization interweaving(OTPI)is proposed innovatively.The experimental results show that a single-wave 224 Gbit/s line rate can be achieved by utilizing commercially available MZM modulators with a 3d B bandwidth of 25 GHz,which greatly relaxes the stringent demand of using high bandwidth components and considerably reduces the overall system cost.A high-power budget and high-speed optical access network system is investigated,where the interaction of the EML’s chirp,fiber chromatic dispersion and self-phase modulation are theoretically analyzed in the intensity-modulated direct-detection(IM-DD)optical access network systems.Based on EML modulation characteristics,by adjusting the bias voltages,the joint effects of EML’s chirp,chromatic dispersion and self-phase modulation are well balanced,a DOF enabled multi-channel multiplexing and demultiplexing technique with DSP-improved network flexibility,reconfigurability and transparency to signal modulation formats is proposed and investigated.By utilizing a nonlinear compensation algorithm and a 10-GHz EML,a line rate of 25 Gbit/s and a power budget of 26 d B are achieved in the multi-carrier optical access network system.2)To mitigate the chromatic dispersion-induced power fading effects in the optical double-sideband transmission systems,the single-sideband transmission systems with high dispersion robustness are studied.First of all,different optical single-sideband generation methods are explored,which can be classified into two categories: 1)intensity modulation techniques with optical filtering;2)special modulator-enabled techniques such as dual-arm Mach-Zehnder modulator(DDMZM)and dual-parallel Mach–Zehnder interferometer modulator(DPMZM).Their corresponding advantages and disadvantages are extensively discussed.A cost-effective optical access network system that combines orthogonal frequency division multiple access(OFDMA)and carrier suppression optical single sideband(CS-OSSB)modulation is proposed.The impact of laser linewidth and CSPR on performance of the signal is investigated.The research results show that the receiver sensitivity can be improved by 4 d B compared with the traditional OSSB technique.Meanwhile,a low-cost bidirectional optical OSSB direct detection optical access network system with carrier reuse and alleviated Rayleigh backscattering effect is proposed for the first time.In the OLT,the DOF-enabled multiplexing/demultiplexing technique is adopted to generate OSSB signals,which makes the system not only more robust to chromatic dispersion,but also provides multi-ONU subscribers with flexible access.At last,the alleviated Rayleigh backscattering effect and the colorlessness of the OUNs are effectively realized by both simulations and experiments.3)Aiming at the issues of high PAPR in the multi-carrier systems,a new type of pruned DFT-spread FBMC signal with low PAPR in OSSB optical access network systems is proposed,using high spectral efficiency FBMC modulation and OSSB technique.It has dynamic network bandwidth allocation,high network flexibility and excellent dispersion tolerance.More importantly,its PAPR performance is better than both the DFT-spread FBMC technique and single carrier frequency division multiple access technique.As a direct result of considerable RAPR reduction,it relaxes the stringent requirement on linear operation ranges of amplifiers,modulators and other components,and greatly reduces the requirements on the high quantization resolution of the digital-to-analog converter(DAC)/analog-to-digital converter(ADC).The effect of the truncated factors of FBMC’s shaping filters on the resulting signal PAPR and performances is investigated.A 50-Gbit/s pruned DFT-spread FBMC over 50-km optical access network system is demonstrated.The proposed innovative scheme has the research value for the evolution of the future 50 G low-cost multi-carrier optical access network.4)To provide flexible and dynamic network multi-service connectivity in the next-generation optical access network systems,a flexible all-optical virtual private network(VPN)communication in IM-DD cost-effectively optical access network system is proposed innovatively utilizing digital orthogonal filter access(DFMA)technique,which concurrently supports upstream and VPN communication.By exploiting the unique advantages of DFMA technique i.e.,excellent modulation format transparency and digital filter allocation flexibility,it has highly flexible characteristics.Since the flexibility of filter,the proposed all-optical VPN optical access network systems have excellent recycling and redistribution of VPN communication.The transmission of concurrent DS,US and VPN with DFMA embedded different modulation formats technique over 25-km SMF are successfully achieved,which verified the flexibility of the DMFA all-optical VPN communication in the optical access network system.