Microwave Signal Generating Based On Stimulated Brillouin Scattering And Its Application

With the development of optical communication in recent years,a new disciplinemicrowave photonics emerged.Now it has been widely used in national defense,communication,satellite and so on.Microwave signals can be generated,processed and transmitted by using optical methods.This thesis mainly studies the generating of microwave signals based on Stimulated Brillouin Scattering(SBS)effect and its application in temperature sensing.Firstly,this thesis summarized the concepts,development history and research directions of microwave photonics.Then,three optical generation methods of microwave signal are introduced in detail.Then,the physical generation process,Brillouin gain spectrum,threshold characteristics of SBS effect are discussed;and then,the principle of sensing schemes based on SBS effect are briefly demonstrated.Next,generation of microwave signal based on the first-order SBS effect is studied and demonstrated experimentally.Microwave signal with different frequency has been generated by utilizing SBS effect in different types of optical fibers,and comparisons have been given.In addition,two generation schemes of high-frequency microwave signal have been proposed and demonstrated,that is 1)Beating signals of second-order Stokes light and optical carrier,and 2)Beating signals of optical carrier and higherorder Stokes light employing a fiber recirculating ring.Finally,a frequency conversion method based on a modulator and SBS effect has been studied.After that,a temperature sensing scheme based on high-frequency beat signal generated by high-order SBS effect in fiber recirculating ring is proposed.Based on the temperature characteristics of Brillouin frequency shift,temperature sensing can be realized by measuring the beat frequency of high-order Stokes light and pump light,and the sensing sensitivity can be improved.Different sensing sensitivities can be achieved by measuring the beat frequency of different orders of Stokes light and pump light.In order to reduce the difficulty and cost of measurement,a down-conversion block is introduced to convert high frequency beat signals into low frequency signals.Finally,a conclusion of this thesis has been arrived,and several suggestions have been made for the future work.