| In the last decades,microwave photonics,as an interdisciplinary subject combining microwave technology and photon technology,has attracted the attention of many researchers.Photonic microwave generation technology,one of the key technologies supporting the microwave photonics,utilizes a photonics method to generate microwave signals.It has the advantages of high frequency,ability to transmit in optical fibers,immunity to electromagnetic interference,and easy wavelength division multiplexing.The common optical microwave technologies mainly include optical heterodyne,modulation method,harmonic filtering method optoelectronic oscillator methods,and nonlinear dynamic characteristics based on optically injected semiconductor lasers.These schemes have their own advantages.Among them,the method of generating microwave signal by the nonlinear dynamic characteristics of optical injection semiconductor lasers has attracted great attention in the industry because the microwave signal obtained by this way has the advantages of high frequency,large frequency tunable range,integration and miniaturization.This work is based on the dynamic characteristics of semiconductor lasers,especially research the generation of photonic microwave signals by using period-one(P1)oscillation.The following works have been accomplished.First,the background,technical principle and advantages of microwave photonics are introduced.Several kinds of technology to generate photonic microwave and theirs advantages and disadvantage are presented.The research progress of photonic microwave generation and microwave signal processing based on the nonlinear dynamics of the semiconductor lasers is overviewed.Next,the rate equations are derived for semiconductor lasers under free-running,optical injection and optical feedback,respectively.Finally,the all-optical microwave signal generation based on period one oscillation and feedback modulation of semiconductor laser under external optically injection is experimentally explored.In this scheme,the DFB-LD plays three important roles,which are light source,frequency selection device and optical-optical modulator.By simply adjusting the injection intensity and frequency detuning,the frequency of the generated microwave signal can be tuned from 6.42 GHz to 21.36 GHz,and the stability of the microwave signal is thousands of times higher than that of the free running P1 oscillation frequency.The proposed all-optical microwave oscillator has no electric microwave components and avoids the optical-electric-optical conversion.Moreover,the system has low cost and simple structure,which is conducive to integration and miniaturization. |
