Microwave Signal Filtering Based On Optical Frequency Comb

Optical frequency comb(OFC)is consisted of a series of frequency components with uniform equal spacing and a coherent,stable phase relationship.It has been used in many fields such as multi-carrier transmission system,microwave photonic filter,microwave signal measurement and so on.In particular,OFC is of great significance for optical fiber communication and microwave photonics.This thesis starts from the background and purpose.The background,technical features and technical advantages of microwave photonics are firstly introduced.Related concepts,application fields and research significance of OFC are described.Then,the research advances of the generation of OFC and the applications of OFC in communication and signal processing are overviewed.Then,the generation technology of OFC are theoretically analyzed and discussed based on the electro-optical external modulation.Two kinds of schemes using intensity modulation and phase modulation,are discussed correspondingly.For intensity modulation,the OFC generation scheme based on the single intensity modulator and the cascade intensity modulator are demonstrated.The typical schemes are theoretically derived and analyzed.For phase modulation,the generation scheme of OFC based on multi-frequency phase modulation are introduced and theoretically analyzed.Next,OFC is used to perform the microwave frequency measurement based on the OFC-enabled channelizer.The scheme uses the dual-OFC structure.Due to the broadband advantage of photonics method and the channelized filter model,the poor measurement precision of microwave signal measurement scheme based on traditional channelization devices can be overcome.After the scheme model is established,theoretical analysis and simulations are carried out.Finally,the microwave frequency measurement is achieved in the wide band frequency range of 2~18GHz with 32 channels and the accuracy is estimated to be MHz.OFC is then used to design microwave photonic filter.Using a fully digital programmable OFC,a programmable microwave photonic filter based on stimulated Brillouin scattering is proposed.The principle,simulation,experiments scheme are described,according to the filtering model established.In experiments,a reconfigurable microwave photonic filter is achieved,showing a tunable range of 100MHz~1.2GHz,flat top of passband responses and tunable central frequency in a range of 4~24GHz.Compared with most of the microwave photonic filters based on analog signal control,this microwave photonic filter scheme is fully digitally controlled and programmable.