Research On Key Technologies And Application Of Novel Dual-loop Optoelectronic Oscillator

With the rapid commercial development of 5G mobile communication and the pre-research of 6G mobile communication,the carrier frequency of wireless mobile communication will be pushed to the frequency band above millimeter wave.The phase noise performance of conventional microwave oscillators such as crystal oscillators and electrical oscillators will degrade significantly as the output frequency rises to millimeter waves.The microwave signal generated by optoelectronic oscillator(OEO)based on microwave photonics technology has the characteristics of both ultra-high frequency and ultra-low phase noise.Therefore,it has a wider application prospect in future 5G mobile communications and microwave photonics systems.However,OEO is difficult to be widely used due to its poor stability and large size.Therefore,it is urgent to study ultra-low phase noise,high stability,large frequency adjustment range,and compact OEO.This paper is dedicated to research ultra-low phase noise,high stability,large frequency adjustment range,and compact OEO.The application of OEO in microwave photonics systems is also studied.The specific contents of this thesis are listed as follows:(1)The basic principles of single-loop OEO,double-loop OEO,and tunable OEO are studied,including the basic structure of OEO,open-loop transfer function,threshold conditions of OEO,oscillation frequency,and noise characteristics.The advantages and disadvantages of single-loop and dual-loop OEO with different structures and the frequency adjustment characteristics of OEO are compared and analyzed by theoretical derivation and simulation.(2)Two kinds of self-polarization-stabilization dual-loop OEO are proposed.Faraday rotator mirrors(FRM)is used to solve the power stability problem of the polarization multiplexed dual-loop OEO output caused by changes in the external environment.The experiment verified that the output optical power fluctuates only 0.05 dB within 3 minutes.A polarization-dependent phase modulator and a polarizer are used to implement a simple structured phase modulation to intensity modulation(PM-IM)conversion.A self-polarization-stabilization dual-loop OEO based on Mach-Zehnder modulator(MZM)is experimentally demonstrated.The side-mode suppression ratio and the single sideband phase noise of the generated signal are 69 dB and-116 dBc/Hz at 10 kHz offset,respectively.A self-polarization-stabilization dual-loop OEO based on a polarization-dependent phase modulator is also tested experimentally.The side-mode suppression ratio and the single sideband phase noise of the generated signal were 63 dB and-114.1dBc/Hz at 10 kHz offset,respectively.(3)Two kinds of compact broadband tunable OEO based on multi-core fiber are proposed.The frequency adjustment range of OEO is improved by using heterogeneous multi-core fiber and PM-IM conversion.Simulation tests have shown that its frequency adjustment range is from 10 GHz to 30 GHz,and the single-sideband phase noise is-149 dBc/Hz at 10 kHz offset.The output frequency and output power stability of OEO are improved by self-polarization-stabilization technology and multi-core fiber,contributing to stable and compact broadband tunable OEO.In our experiments,its frequency adjustment range is from 3.5GHz to 17.1GHz.The side-mode suppression ratio and the single sideband phase noise of the generated signal are 61 dB and-100 dBc/Hz at 10 kHz offset,respectively.The frequency drift and power drift within one hour are 0.59 ppm and0.44 dB,respectively.(4)A microwave photonic RF front-end based on an optical IQ modulator is proposed.An optical IQ modulator is used to simultaneously achieve RF signal self-interference cancellation,OEO and down conversion.The side-mode suppression ratio and the single sideband phase noise of the self-generated local signal are 52.56 dB and-108.66 dBc/Hz at 10 kHz offset,respectively.The frequency drift and power drift within one hour are 4ppm and 0.51 dB,respectively.This experiment has realized the down-conversion of the center carrier frequency 12.6GHz RF signal to 2.6GHz.