Optical And Microwave Frequency Measurements Based On Optical Frequency Comp Generation By Reciruclation Modulation

As a special optical source with stable frequency domain comb characteristics and good time domain coherence,optical frequency comb has important applications in the field of absolute frequency measurement.Frequency measurement based on optical frequency comb has some advantages that traditional measurement methods do not have,such as larger measurement range and no image frequency interference(the frequency to be measured will generate the same frequency difference frequency on both sides of the detection frequency),measurement accuracy more precise.Aiming at the flexibility of generating optical frequency comb based on modulation method and combining the design of optical frequency comb frequency relationship,this paper proposes to use circular modulation optical frequency comb instead of traditional optical frequency comb to measure light wave and microwave frequency.The main research contents are as follows:1.The optical frequency comb is generated by suppressing the carrier single sideband cyclic modulation.The principle of frequency modulation generating the frequency sweep and the equal phase difference optical frequency comb is analyzed.The simulation model is established on the VPI software to verify the feasibility of the scheme.The amplitude-frequency curve of the optical comb can be modulated by controlling the gain of the optical amplifier in the loop to produce a flat or equal-order incremental/decreasing optical comb.In the process of cyclic modulation,the accumulation of optical amplifier noise affects the carrier-to-noise ratio of the optical frequency.When the power of the modulated light source is large,the carrier-to-noise ratio is relatively large.When the power of the modulated light source is small,the number of cyclic modulation increases.This will result in a reduction in the carrier-to-noise ratio,which will reduce the flatness of the optical comb.2.The equal-frequency swept frequency optical comb produced by cyclic modulation is used to measure the optical frequency,which eliminates the problem of image frequency existing in the traditional optical comb measurement.In the case of recording the number of cyclic modulations,the linear difference frequency relationship can be adopted.The measured optical frequency is predicted.In order to avoid the recording of the number of cyclic modulations,the amplitude of the frequency-swept combs is nonlinearly modulated,and the range of the range of the measured optical frequencies is determined by detecting the amplitude ratio of the two minimum difference signals,combined with the difference frequency values.Obtain the measured optical frequency.In order to avoid the sweep time,the optical frequency combs generated by the cyclic modulation are used for nonlinear frequency-frequency modulation to measure the optical frequency,and the feasibility of eliminating the image frequency to obtain the accurate optical frequency is analyzed.3.A method for generating equal-amplitude RF comb by two-way equal-phase optical frequency comb balance detection is designed.Multi-multiplier is used to multiply the measured amplitude by multi-frequency amplitude modulation of the equal-amplitude RF comb.Frequency and amplitude ratios of the frequency enable microwave frequency measurements.The method converts the high frequency microwave signal into a low frequency signal for frequency measurement,avoiding the frequency sweeping process,and the measurement bandwidth is mainly determined by the bandwidth of the photodetector.The feasibility of the method is verified by simulation.