Research On The Generation And Processing Method Of Radio Over Fiber

With the development of ultra-high speed and ultra-bandwidth of 5G wireless communication,users’ demand for high-speed streaming media is increasing which requires the communication network to have the characteristics of large capacity,high speed and low delay.Spread spectrum resources can achieve the communication goal of large capacity and high rate.With the increase of operating frequency,the loss of wireless channel will also increase.Radio over fiber(RoF)which combines optical fiber communication and wireless communication can effectively solve this problem.RoF technology uses the characteristics of low loss and high broadband of optical fiber to improve the bandwidth of wireless access network and provide users with flexible and convenient services.It has become a research hotspot at home and abroad.Based on the study of RoF technology,this thesis focuses on the satellite processing scheme based on photon frequency conversion,the band selection communication system based on optical frequency comb and the frequency doubling selection system based on polarization multiplexing modulator.The main work and innovations of this thesis are as follows.(1)To solve the problem that radio frequency conversion in satellite system is not flexible and complex in frequency selection,a satellite onboard processing scheme based on photon frequency conversion is proposed.The received signal is converted into optical signal by electrooptic modulator and the on-board frequency conversion is realized by photon frequency conversion.The frequency conversion between Ka/Q/V bands in 8PSK modulation format is simulated.The results show that this scheme can successfully realize the frequency conversion between Ka/Q/V bands in 8PSK modulation format.(2)To solve the problem of co-frequency interference and high system complexity,a scheme of band selection communication system based on optical frequency comb is proposed.When the bit error rate increases sharply due to interference,the co-frequency interference can be avoided by changing the local oscillator frequency to generate RF signals of other frequencies.The simulation results show that this scheme can effectively avoid co-frequency interference and the adjusted signal bit error rate is basically the same as that without interference.At the same time,the system using optical frequency comb as local oscillator light source can realize the transformation of multiple frequency bands.This scheme can reduce the cost and complexity of the system.(3)To reduce the cost of frequency doubling system and improve the flexibility of frequency selection,a frequency doubling selection system based on polarization multiplexing modulator without optical filter is proposed.The system utilizes polarization multiplexing modulator to modulate the polarization states of the add and drop channels in different ways which can achieve doubling frequency selection.In this simulation,different frequency multiplication signals are obtained by adjusting the angle of the polarizer and the voltage amplitude and phase difference of the RF signal input the polarization MZM.The research results show that the system can set the angle of the polarizer according to the voltage amplitude of the RF signal and selectively obtain the double frequency,quadruple frequency and twelve frequency signal.