Research On Key Technologies Of Optoeletronic Oscillator

Optoelectronic oscillator is a new type of oscillator system for generating microwave signals.It has the characteristic of low phase noise,high Q value and high spectral purity.It is widely used in communication,radar,transmission,sensation and many others fields,so it is very meaningful for the research of optoelectric oscillators.This paper first introduces the research background,the research status and the significance of optoelectronic oscillators,then we deduces its theory in detail,and we builds an experimental system based on theoretical analysis,and we anslyze the influence of the effect of fiber length on phase noise and thr optoelectronic oscillator system on double ring.Based on the basic theoretical model of optoelectric oscillator,two experimental systems are proposed:1.Phase noise and spectrum stability are important indicators to measure microwave signal.This paper proposes a phase noise optimization system based on optoelectronic oscillator.The system is consist by dual-parallel MZM and optoelectronic oscillator loop.The light is modulated by the RF signal through the DPMZM,a positive and negative second-order sideband is generated by adjusting the bias point above and below the DPMZM.The optical sideband enters the optoelectronic oscillator system and the signal is selected,amplified and enhanced by optoelectronic oscillator loop,a quadruple frequency signal is generated.The frequency of the output signal is changed by adjusting the frequency of the RF signal.In the experiment,we can change the frequency of modulated signal and then we can get a tunable singal of 2-12 GHz frequency.The spurious suppression ratio is 40 dB@12 GHz,and the side mode suppression ratio is 55dB@12 GHz.In the experiment,the phase noise of the microwave signal obtained by the photoelectric oscillator system at the 6 GHz signal is optimized by the phase noise of the direct quadruple frequency signal by 11 dBc/Hz@10 kHz,which solves the phase noise deterioration of the multiplier in the optical external modulation system and stability of optoelectronic oscillator.2.Considering the miniaturization and applicability of the whole system,a microsphere cavity-based optoelectronic oscillator system is proposed.This chapter introduces the theoretical basis of the coupling of microsphere cavity and taper fiber.The microsphere cavity was prepared in the laboratory.The quality factor of the microsphere cavity was measured and it was reached3×10~7.We deduces the theoretical of a microsphere cavity based opto-electronic oscillator system,the microwave signal with a frequency signal of 8.8 GHz was measured and the spurious suppression ratio reached 45dB,the side mode suppression ratio reached 40 dB.Because of the high Q value and low loss of the microsphere cavity,it can have both the filtering effect and the energy storage component of the loop.On the one hand,it solves the problem of frequency drift which caused by the external temperature on the optical fiber.On the other hand,it can select a single mode of the loop due to the high Q value.The system has a simple structure and it is of great significance for miniaturization in the future.