Study On Performance Optimization Of RoF-PON System Based On OFDM

With the rapid development of the communications field and the continuous improvement of people's living standards,people's demand for data traffic has shown an explosive growth trend.Large bandwidth,high speed,low delay,flexible and diverse access methods,and other user needs have made traditional access network difficult to fulfill this difficult mission.Therefore,it is of great practical significance to study the next-generation new access network.In the future,the access network can provide users with optional wired/wireless access methods.The implementation of this method can be realized by combining RoF technology with PON technology.On this basis,the introduction of orthogonal frequency division multiplexing(OFDM)technology can improve the frequency band utilization rate and effectively suppress the dispersion effect caused by long-distance fiber transmission.This paper focuses on the construction of RoF-PON access system and the optimization of RoF-PON system transmission performance by suppressing the higher peak-to-average power ratio(PAPR)of OFDM signals.Firstly,the high-frequency millimeter wave generation technology in RoF technology is studied.Selecting the appropriate generation of high-frequency millimeter wave is the key to RoF technology.The thesis analyzes the specific principles,advantages and disadvantages of four high-frequency millimeter wave generation technologies:direct intensity modulation technology,optical heterodyne technology,optical frequency doubling technology,and external modulation technology.The external modulation technology was selected as the scheme to generate 60GHz high-frequency millimeter wave in the system.Then,the advantages and disadvantages of the three sideband signals generated by the external modulation method:double sideband(DSB),optical carrier suppression double sideband(OCS),and single sideband(SSB)were simulated and analyzed.Finally,single-sideband modulation is selected as the modulation format for the uplink and downlink signals in the system.Secondly,this thesis studies the colorless optical network unit(ONU)technology in the PON system.This article analyzes four ONU colorless technologies of specific technical principles and advantages or disadvantages:based on wavelength tunable laser technology,based on broad-spectrum light source segmentation technology,based on FP-LD laser technology,and based on wavelength reuse technology.The reflection-based semiconductor optical amplifier(RSOA)wavelength reuse technology was selected as the colorless ONU scheme in this system.Then,based on the RSOA implementation of the ONU colorless scheme,an OFDM-RoF-PON system was constructed,and the transmission performance of the OFDM-RoF-PON system was analyzed.The results show that when the downlink signal uses a single-sideband 4/16QAM modulation signal with a transmission rate of 10Gbit/s,the system transmission bit error rate can reach 10~-1010 when the received optical power is-19.5dBm,which meets the actual transmission needs.When the system uses an NRZ signal with a transmission rate of 10 Gbit/s,the eye pattern of the system is more open,and the transmission performance is better.Finally,this thesis studies several techniques to suppress high PAPR of OFDM signals:limiting techniques,coding techniques,and probability techniques.The improved Selective mapping(SLM)technology of coding techniques is selected to reduce PAPR of OFDM signals in the systems.The improved SLM technology has the advantages of low computational complexity and better ability to suppress PAPR.Later,the improved SLM technology is introduced into OFDM-RoF-PON system to suppress the non-linear effect of the system,so as to optimize the transmission performance of the system.Through simulation analysis,the results show that the improved SLM technology has a better ability to suppress PAPR than the traditional SLM technology,and can generate more candidate signals with lower computational complexity.At the same time,after introducing the improved SLM technology in the OFDM-RoF-PON system,the nonlinear effect of the system is suppressed.Under the same optical signal-to-noise ratio,the system using the improved SLM technology has a lower transmission bit error rate,and the system transmission performance is better.