Research On Key Techniques Of ROF System Based On Multi-carrier Generator

Microwave photonics is a new field which combines microwave science and photonics.Its research mainly includes high frequency microwave generator,the photon signal processing technology,ROF access system and so on.Among them,ROF technology combines the traditional optical fiber communication and wireless communication technology,which can make it realize wireless broadband access up to Gbps.Thus,it provides an opportunity for future large capacity network communication.Under the supports of the National Nature Science Foundation of China,this thesis is devoted to carry out a series of theoretical,simulation and experimental research on multi-carrier generator,high-frequency millimeter wave photon generator,multi-channel signal all optical frequency conversion,optimum optical single sideband modulation system and full duplex WDM-ROF transmission technology.Specific research results and contents are as follows:1.The application of multi-carrier generator in ROF system has been studied experimentally.Multiple optical carrier signal output can be achieved by a FP laser.Although it has the advantage of low cost,it has problems of insufficient spectral range and multi-carrier flatness.On the basis of this,the structure of the ultra-flat multi-carrier generator generated by the cascade of optical modulator is proposed,which can further improve the spectral range of the multi-carrier.The experiment results have verified that the proposed scheme can be implemented.2.The scheme of high-frequency MMW photonic generation based on multi-carrier generator have been proposed and studied.By using the spectral characteristics of multi-carrier generator,high-frequency MMW signals with different frequencies can be obtained by selecting two optical carrier signals with different frequency interval.Thus the frequency range and the performance of the transmission link are further improved.The generation of 440GHz and 480GHz high-frequency MMW signals can be realized respectively.3.The scheme of multi-channel simultaneous all-optical up conversion in ROF system based on multi-carrier generator have been proposed and analyzed.The proposed scheme improves the exisiting inefficient all optical frequency conversion technology.7 signals up conversion to 60GHz millimeter wave simultaneously can be realized through the re-modulation of multi-carrier output spectral.In order to improve the efficiency of all optical up conversion,the following 15 signals up conversion simultaneously by an ultra-flat multi-carrier generator.4.The scheme of ROF bidirectional transmission based on multi-carrier generator has been proposed.Firstly,a ROF bidirectional transmission system based on wavelength reuse has been proposed.The optical carrier of CS is reused to provide the light source for the uplink transmission.In the scheme,we get 60GHz MMW for downlink and realize the modulation and transmission of uplink data simultaneously.In order to improve the spectrum efficiency and system performance,a full-duplex WDM-ROF system based on multi-carrier generator has been proposed.By using the ultra-flat spectral characteristics as multi-channel for WDM system,a full-duplex 1:7 WDM-ROF system with higher spectrum efficiency and lower power cost can be achieved.5.The scheme of single sideband modulation optimization based on fiber bragg grating is proposed and verified through experiment.By using the wide transmission spectrum characteristics of phase shift grating and laboratory made FBG-FP in ROF analog photonic link to realize single side band filter and OCSR adjustment.Then the central optical carrier and one of the sidebands will experience different attenuation degree.Hence the conversion from DSB modulation to SSB modualation can be achieved.At the same time,the OCSR is optimized to OdB,which can greatly improve the ROF analog optical link sensitivity consequently.Besides,we also discuss the issue of the SMF length and optimized OCSR in ROF photonic link.