Research On Key Technologies Of Frequency Comb For High Speed Optical Sampling

Stable sampling pulse light source with high repetition frequency is the key device to realize optical analog-to-digital conversion.The repetition rate of sampling pulse based on mode-locked technology is usually below 1 GHz,which is hard to meet the sampling requirements of large bandwidth and high rate.Optical frequency comb is comb spectrum with equal intervals,which is a pulse sequence with equal intervals in time domain.As a new sampling pulse source,the repetition frequency of the optical frequency comb generated by electro-optic modulation can be flexibly tuned in the range of tens of GHz,which can break through the instantaneous bandwidth bottleneck of the traditional pulse mode-locked laser,and has a broad application prospect in high-speed and high-precision optical sampling systems.Aiming at the application requirements of silicon-based integrated optical sampling system,the simulation design and experimental research of optical frequency comb for high-speed optical sampling are carried out in this paper.The main tasks are as follows:1.Through simulation calculation,an electro-optic comb generation scheme based on dual drive Mach-Zehnder intensity modulator is designed.In the experiment,11 combs with flatness less than 2 d B and repetition frequency between 10 GHz and 20 GHz are generated.After cascading them with two phase modulators,21 combs with flatness of about 3 d B are generated.2.The link design and optimization of nonlinear spectrum broadening are carried out based on electro-optic comb.In the experiment,by introducing nonlinear optical effect,the broadened spectrum with flatness within 5 d B is obtained in the range of 1551 nm to1555 nm and 1545 nm to 1549 nm.The ultrafast time domain characteristics of the broadened optical frequency comb are analyzed by FROG pulse detection technology.3.Through dispersion regulation and optimization,tellurite microstructure fiber with flat all positive dispersion and all negative dispersion near 1550 nm is obtained,and a broadband optical frequency comb generation scheme based on electro-optic modulation and cascaded positive and negative dispersion tellurite microstructure fiber is proposed.Finally,an optical frequency comb covering more than 170 nm in 6 d B spectral bandwidth is generated.4.The electro-optic comb obtained by nonlinear spectrum broadening is used as the sampling pulse light source to realize the simulation design of high speed optical sampling system.The repetition frequency of sampling pulse is further increased to 40 GHz through time wavelength interleaving,which is applied to the sampling of 10 GHz sinusoidal signal and NRZ code signal.The feasibility of electro-optical frequency comb for high-speed optical sampling is verified,and the amplitude jitter of sampling pulse under 4 channel and 8 channel time wavelength interleaving schemes is further evaluated.The research of this paper lays a foundation for the research of frequency comb suitable for optical sampling applications.The research results have important reference value for providing suitable sampling pulse source for high speed optical sampling module with bandwidth above 20 GHz.