Research On Advanced Modulation Technology For 5G Fronthaul Optical Carrier Network

With the rapid development of cloud services,video streaming services,and mobile interconnection services,there occurs an urgent requirement of transmission capacity in the 5G fronthaul optical carrier network.The increasing bandwidth demand in the fronthaul carrier network segment requires not only higher transmission speed but also lower costs.The intensity modulation and direct detection(IM/DD)optical transmission is considered to be the more attractive and feasible solution for short reach optical transmission due to its simple structure,low computation complexity and power consumption.However,the bandwidth of a mature commercial low-cost optoelectronic device is generally limited,it is significantly smaller than the baud rate of the signal at high data rate.Considering the limited bandwidth of low-cost optics,advanced modulation formats with spectral efficiency and advanced digital signal processing(DSP)are researched in order to reduce the baud rate of the signal.However,complicated DSPs need high-speed digital-to-analog converters(DAC)or analog-to-digital converters(ADC),which greatly increases the complexity and cost of the system.This is not cost-effective for cost-sensitive optical network units located at the user side.Therefore,for high-speed short reach systems based on intensity modulation and direct detection,advanced modulation schemes such as multi-level pulse amplitude modulation(PAM),carrier-less amplitude and phase modulation(CAP)and discrete multi-tone modulation(DMT)are the most potential research topics due to its simpler DSP architecture and lower complexity.In this thesis,for fronthaul carrier network system based on bandwidth limited optics,advanced modulation formats with high spectral efficiency are studied.The main research work and innovations for advanced modulation formats in short reach optical transmission systems are as follows:(1)A joint IM/DD fiber optic communication simulation platform based on bandwidthlimited optics is demonstrated.containing transmitter,DAC,fiber,optical attenuator,receiver and ADC.The transmission of different modulated signals is achieved by simple equalization method.(2)Performance comparison of advanced formats with high spectral efficiency,are carried out using the same simulation setup in 50 Gb/s/λ PON in terms of the performance and DSP complexity.The receiver sensitivity and power budget of three formats are simulated after 20 km SSMF transmission.The results show that over 29 d B power budget at HD-FEC threshold based on bandwidth-limited optics can be achieved.(3)A comprehensive comparison of advanced modulation formats with high spectral efficiency is carried out in 100 Gb/s/λ optical system based on bandwidth-limited optics at Oband.The receiver sensitivity and power budget of three formats are simulated after 20 km SSMF transmission.The results show that over 25 d B link loss budget at HD-FEC threshold can be achieved.The performance of thermal noise and chromatic dispersion are discussed.