Research On The Key Technology Of Coherent Optical Comb With High Signal-to-noise Ratio

The optical frequency comb refers to a series of optical lines with the same frequency spacing and the same amplitude,and the shape is similar to the comb,and has good stability.In microwave photonics,optical frequency comb as a very effective technology plays an important role in many systems such as optical communication.In addition to its application in the field of microwave photonics,optical frequency combs are used in optical sensing,clock distribution,and high.It has a wide range of applications in precision measurement and ranging and waveform synthesis.Based on the above reasons,the main work of this paper is to study the design of high-signal-to-noise ratio coherent optical frequency comb,and solve the key technical problems involved in the scheme,and then further improve the scheme based on this.As well as theoretical analysis and experimental verification.This paper first introduces microwave photonics as the starting point,and expounds the research status of optical frequency comb at home and abroad.It introduces the mechanism and principle of optical frequency comb,and designs the cascade based on modulator.The optical frequency comb production schemes of the method,the cyclic frequency shift method and the nonlinear effect method based on the optical fiber are then theoretically analyzed and experimentally verified.However,based on the first two generation methods,the number of optical frequency comb lines is small and the stability is poor.Nevertheless,the optical frequency comb based on the nonlinear effect method of the optical fiber can greatly broaden the spectrum,but the flatness is not good.These several solutions can not meet the requirements of broadband flat optical comb in practical applications.Secondly,we propose a design scheme that can generate high SNR coherent optical frequency comb,and list the key technical problems involved and solve them one by one,focusing on the construction of parameter mixer and HNLF dispersion optimization.problem.For HNLF dispersion control,a fiber winding machine capable of optimizing HNLF dispersion has been developed.The machine is used to apply longitudinal strain to the fiber to broaden the SBS gain spectrum to further realize the spectral broadening of the optical frequency comb and improve its flatness.On this basis,we construct an OFC generator that can generate a high signal-to-noise ratio coherent optical frequency comb,and explain its theoretical basis and then verify the scheme through experimental demonstration.The optical pulse generated by the modulator cascade method is used.As a seed source for spectrum broadening,it is subjected to pulse compression after passing through a parametric mixer;then,105 m HNLF1 without strain applied and strain applied is placed in the optical link,respectively,by comparing the two spectra,the strain is applied.HNLF1 has little effect on improving the flatness of the optical comb,so it is less feasible to use this method to improve the frequency comb performance.Then,based on the scheme,the wideband optical frequency comb is shaped by introducing WaveShaper.In the wavelength range of 1538-1565 nm,the flatness is about 4dB,the resolution bandwidth is 0.1nm,and the signal-to-noise ratio is about 15 dB.The high-quality optical frequency comb with the number of teeth is about 270,and the feasibility of the scheme is verified by experiments,which provides a good foundation for the subsequent optical frequency comb experiment.