Application Research Of Multi-dimensional Multi-order Modulation Technology In Optical Wireless Communication System

Radio over fiber(RoF)is one of the key technologies in the future broadband wireless access because of its advantages such as high speed,large capacity and flexible access.Meanwhile,it is of great theoretical significance and practical value in the application of RoF to take into account that the use of multi-dimensional multi-order modulation can further improve the bandwidth efficiency and reduce the budget cost of transceiver system.In this paper,basic modulation and demodulation principle of several common modulation formats(including RZ/NRZ,PSK and QAM)and several new modulation formats(including OFDM,DMT and PAM and etc.)are analyzed.The electro-optical modulation and high-frequency signal demodulation technology in RoF system are also analyzed,and the application characteristics of optical heterodyne technology are introduced.On above basis,the use of multi-dimensional multi-order modulation technology in RoF system is studied.Results of the specific research content,simulation or experimental are as follows:Related theoretical exposition and experimental study of multi-dimensional multi-order modulation technology using in RoF systems are presented,an application scheme of 10Gbit/s 4PAM-RoF optical access system is proposed and proved,and has successfully realized 40km optical fiber without error transmission.An application scheme of 60GHz 4/16/64QAM-OFDM RoF optical access system is proposed and proved,and the performance of transmission signals are analyzed and compared by using three kinds of arrangement(adjacent,interleaved,random)of subcarriers.A full-duplex optical-generated OFDM millimeter-wave access scheme is proposed and proved.The downlink transmits 64QAM-OFDM modulation signal and the uplink transmits 8PSK-OFDM modulation signal.The results show that in the downlink,when the receiver is-18dBm and the number of subcarriers is 256,the BER is close to 10-3.7,and the receiving sensitivity is the best.When the received power of the uplink is higher than-28.5dBm,the BER of the received signal is lower than 10-3.A new scheme for transmitting 128QAM-OFDM signal in the downlink of the terahertz over fiber(ToF)access system is proposed and proved.The results show that the 128QAM-OFDM signal not only has higher spectral efficiency,but also the value of the receiver sensitivity is lower than-lOdBm when the bit error rate(BER)is 10-3.A design of a real-time indoor visible light communication(VLC)utilizing white LED as the light source is proposed and investigated.The results show that the bit error rate is less than 10-6 while the receiver sensitivity is higher than-32dB.