Research On The Generation Of Optical Frequency Comb Based On Pulse Signals And Its Application In Digitally Controlled Microwave Frequency Comb

Optical frequency comb(OFC)is composed of a series of optical signals which are discrete in the time domain,have equal frequency intervals and approximately equal power in the frequency domain.It can simultaneously provide multiple optical signals of different frequencies and approximately equal power in a continuous frequency band.OFC has the advantages of equal frequency spacing and high precision.It has attracted great interest due to its wide range of applications,including radio over fiber communication,lidar systems,microwave frequency comb generation,precision measurement,channelized transmission and reception systems,etc.However,in the existing OFC,it is difficult to cope with the complex application requirements due to the complex structure,less combing and low power flatness.In order to solve this technical problem,the research background and significance of OFC were clarified at first in this paper.And the existing shortcomings of OFC and the research status were also summarized.Then,an OFC generation scheme based on pulse signal and Mach-Zehnder modulator(MZM)was proposed.The principle of this scheme was introduced in detail,and a perfect theoretical model was established.By using optical simulation software Optisystem,the relationship between the system parameters and the frequency spacing of OFC,the number of comb-lines,the power variation and the spectrum coverage were analyzed.The scheme of OFC generation has many advantages such as simple structure,easy to implement,large number of comb-lines,tunable frequency spacing,and good power variation.It solves the problems of the OFC device in the prior art,including complex structure,the relatively large dependence on the radio frequency signal source,fewer numbers of comb-lines and huge power variation,etc.In addition,based on the proposed OFC technology,a digitally controlled microwave frequency comb(MFC)application scheme based on pulse signal and MZM is proposed.The principle of the scheme was introduced in detail,and a perfect theoretical model was established.By using optical simulation software,the relationship between the system parameters and the frequency spacing of MFC,the number of microwave signals,power variation and spectrum coverage was analyzed.The MFC generated by this scheme has a wide coverage range,which can cover the frequency bands of decimeter wave,centimeter wave and millimeter wave at the same time.It solves the problems of complicated structure,fewer number of microwave signals,huge power variation and narrow spectrum coverage of the MFC in the prior art.Besides,by designing the waveform of the pulse signal,the number of microwave signals and the power variation of the MFC can be tuned.By changing the binary bit sequence,the frequency spacing of the MFC can be tuned digitally.The combination of microwave photonic technology and computer numerical control technology is realized,which has broad application prospects.