Research On Advanced Modulation Formats And Their Applications In Radio-over-Fiber System

Radio-over-Fiber(RoF)is one of key technologies in future broadband wirelessaccess It can use huge bandwidth of fiber to reduce the cost and guarantee thewireless communication flexibility In order to reduce cost of RoF system andpromote its commercializing,it is necessary to resolve some key problems such astransmission distance of millimeter-wave signal which will be limited by chromaticdispersion of fiber and further simplifying structure of base station and SO onTherefore,the investigation on the high speed advanced modulation format,whichcan overcome chromatic dispersion of fiber and improve spectrum efficiency,andfull-duplex RoF system with simple base station as well as generation of highperformance-to-price optical millimeter-wave are of great significance in both theoryand practice,which can promote research work on transmission and application inRoF system In the dissertation,we investigate some key technologies in advancedmodulation format and their applications Our innovation work and results are mainlyfocused on the following aspects:Firstly,advanced modulation format becomes a hot-spot research in 40Gb／s andabove long-haul optical transmission The use of differential phase-shift keying anddifferential quadrature phase-shift keying modulation format has been demonstratedas an effective scheme to manage signal impairments arising from fiber nonlineareffects and polarization mode dispersion Considered that the photoelectriccomponent'S speed will limit the generation of high speed advanced modulationformat,we have proposed a novel scheme to generate 80Gb／s return-to-zerodifferential phase-shift keying,carrier-suppressed return-to-zero differentialphase-shift keying,return-to-zero differential quadrature phase-shift keying andcarrier-suppressed return-to-zero differential quadrature phase--shift keying based on a proposed system model After analyzing the tolerance of polarization-modedispersion on different modulation format,the simulation results show-thatcarrier-suppressed return--to--zero differential phase-shift keying has more tolerance ofpolarization mode dispersion than that of return-to-zero differential phase-shiftkeying by comparing their eye open Meanwhile the spectrum structure ofcarrier-suppressed return-to-zero differential quadrature phase-shift keying has morecompact than that of return-to-zero differential quadrature phase-shift keying,whichmeans to strengthen the tolerance against fiber nonlinear and polarization modedispersionSecondly,the research of millimeter-w-ave band RoF technology can be meetingthe demand of people to have broadband business To realize RoF system'Scommercializing,it is one of key technologies to simplify base station and reducesystem cost in the full-duplex RoF system We have proposed and experimentallydemonstrated a novel full-duplex RoF system based on phase modulator and fiberBragg grating At central station,a phase modulator and a fiber Bragg grating wereused to generate optical millimeter-w-ave The experiment results show-that thepenalty of 2 5 Gb／s upstream data after transmission over 20km single-mode fiber is1 1dB at the BER of 10 In this system,the phase modulator without bias voltage canbe used to reduce system complexity,because it does not need complex electric circuitthe fiber Bragg grating is the passive component,which has lower price to reducesystem cost With frequency enhancement of optical millimeter-w-ave signal,thegeneration of high performance-to-price optical millimeter-w-ave has higher request tophotoelectric component'S bandwidth Therefore it is one of key technologies togenerate high performance-to-price optical millimeter-w-ave signal and alleviate thechromatic dispersion effect by long transmission of fiber We have proposed andexperimentally demonstrated a novel full-duplex RoF system that low frequencymicrowave signal can be used to generate high performance--to--price opticalmillimeter-w-ave,that is to say optical millimeter-w-ave signal with 40GHz can begenerated by radio frequency signal with 10GHz The experiment results show-thatthe penalty of 2 5 Gb／s upstream data after transmission over 20km single-mode fiberis 1 dB at the BER of 1 0～In this system,it can greatly reduce the bandwidth ofmicrowave component and modulator,and the cost of systemFinally,all of the proposed schemes to generate optical millimeter-w-ave signalcan only suppo~on-off keying format(OOK),and none can transmit vectormodulation formats,such as phase-shift keying,quadrature amplitude modulation signals,which are of utmost importance for wireless communication applicationsConsidered that transmission distance will be limited using on-off keying formatbecause of the effect of chromatic dispersion,we have proposed and experimentallydemonstrated a novel full--duplex RoF system based on differential phase--shift keyingmodulation format The experiment results show-that 2 5 Gb／s upstream data anddownstream data can transmission over 40km single-mode fiber successfully In thissystem,it can promote transmission performance of high performance-to-price opticalmillimeter-w-ave signal in full-duplex RoF system Simultaneously considered thato~hogonal frequency division multiplexing(OFDM)had the high spectrum efficiencyas well as the strong tolerance against chromatic dispersion and polarization modedispersion,we have proposed and experimentally demonstrated a novel full-duplexRoF system based on o~hogonal frequency division multiplexing format withfrequency--quadrupled optical millimeter--wave generation and wavelength reuse foruplink connection The experiment results show-that the the power penalty of 2 5 Gb／sOFDM downstream data after transmission over 50km single-mode fiber is about 1dBat a BER of 10～．however the power penalty of the 2 5 Gb／s OOK upstream is lessthan 0 5dB at a BER of 10。after transmission the same distance In this svstem．itdoes not need the coherent source in the base station because of wavelength reuse foruplink connection effectively,which has high spectrum efficiency and reduce the costof system Meanwhile it can be shown that the effect of fiber chromatic dispersion canbe neglected as electrical o~hogonal frequency division multiplexing signal is used,itmeans that downstream data can transmit over single-mode fiber in the long distancewithout chromatic dispersion compensation.