Research On Frequency Tunability And High-precision Relative Distance Measurement Technology Based On Optoelectronic Oscillator

As a new type of high performance oscillator,optoelectronic oscillator(OEO)has attracted more and more scholars' attention and research due to its characteristics of high oscillation frequency,high spectral purity and so on.With the continuous improvement of phase noise and side mode suppression performance of OEO,frequency tunability has become a hindrance to its practical use.How to generate frequency tunable oscillating signals while ensuring low phase noise and high side mode suppression performance has become a research hotspot.Besides the above characteristics,oscillation frequency of OEO is particularly sensitive to changes in cavity length.According to this feature,we introduce the distance to be measured into the OEO loop by utilizing the sensitive characteristic of oscillation frequency to distance change.The measured distance information can be obtained by measuring the oscillation frequency.This method promises high accuracy distance measurement.Based on the above understanding,this paper focus on two aspects of tunable OEO and ranging technology based on OEO:1.In the aspect of study on frequency tunability of OEO,this paper analyzes the research schemes at home and abroad,then proposes a tunable optoelectronic oscillator based on electrical amplifying frequency-selected cavity,and carries out theoretical analysis,simulation analysis and experimental verification.This scheme retains the advantage of low phase noise of single-loop OEO,and adjusts the delay time of the optical delay line in the OEO loop and the bias voltage of the phase shifter in the electrical amplifying selective-frequency cavity to achieve the best matching state which has high side mode suppression effect.The tunable OEO can be established by electrically injection locking between the output signal of selective-frequency cavity and the free oscillation signal of OEO,whose output frequency is determined by the selective-frequency cavity locking the corresponding oscillation mode of OEO.The experimental results show that the output signal with the frequency tuning range of10.05 GHz?10.09 GHz,which is equivalent to 40 MHz,and the tuning step of 417 k Hz is obtained.Its side-mode suppression ratio is 60 d B when the output frequency is10.0519 GHz,and the phase noise is-115 d Bc/Hz@10 k Hz.2.In the aspect of distance measurement technology based on OEO,this paper compares the advantages and disadvantages of traditional laser ranging technology.Based on the existing OEO measurement system scheme,this paper proposes a highprecision relative distance measurement scheme based on dual-wavelength alternately OEO.The scheme controls the working state of the laser of the reference loop and the measurement loop to realize the alternate oscillation of the two loops.High-precision measurement is achieved by using the reference loop to compensate for the cavity length drift of the measurement loop.In the experiment,the optical delay line is used to simulate the change of spatial distance,the standard deviation of the measurement results do not exceed 0.5 ?m.Then we build space optical path for actual testing.Under test conditions of 0 mm,+2 mm,-2 mm,+10 mm,-10 mm,+20 mm and-20 mm equivalent measuring distance,the standard deviation of the measurement results do not exceed 0.8 ?m.