Research On Theoretical Modeling And Several Key Technologies Of Broadband Microwave Photonic Links

Microwave photonics(MWP)has been widely used in the fields of signal generation,transsimision and processing due to its high-speed and broadband advantages.As the limitation of electronic bottleneck continues to increase,in order to meet with the demand for multifunctional,integrated,and intelligent signal processing,MWP is promised to be an innovated way to inherit the applicaton filed of conventional electronic technology.At present,the research of MWP is in the transition stage from system architecture with discrete devices to the monolithic integration,it is necessary to establish standard system design and integration processes for the realization of MWP system in practical applicantion.Hence,the theoretical model analysis and performance optimization of microwave photonic links are important steps to promote the development of MWP.Besides,the theoretical analysis should combine with experimental investigations of key technologies in MWP to achieve the iterative development of system performance.This dissertation focuses on the theoretical modeling and key technologies in system design of broadband microwave photonic links and systems.To explore the technical advantages of MWP,the physical model of a basic MWP link should first be established.Then the key components that consists MWP systems,such as optical pulse source,electronic to optical modulation and all-optical process,are introduced to the basic theory.To verify the feasibility of designed MWP system,experiments are demonstrated for performance evaluation and optimization.The work of this dissertation can be devided into the following aspects:(1)Based on the review and understanding of MWP technology,the basic microwave photonic link can be summarized into three key parts:electro-optical conversion,optical domain signal processing,and optical-electrical conversion.First,the theoretical models of devices that achieve the function of these parts are clarified.Then,the parameters that affects the performance of MWP links are derived and numerically simulated.The analysis of this part provides basic support for the subsequent research.(2)The basic theory of MWP link is expanded with optical pulse source,and the parameters evaluating link performance are illustrated.Specificly,the working mechanism of optical sampling pulse in photonic analog-to-digital converter(PADC)is studied.It is founded that the amplitude and phase changes in longitudinal mode of optical pulse spectrum can affect the quantization results.In experiment,a method is proposed to measure the effect of optical samping pulse on system frequency response.To evelute the bandwidth characteristic under multiple Nyquist bands,an amplitude flucturation parameter is introduced and experimentally verified.Furmore,to instruct the design of sampling pulse,a simulation for the influence of optical pulse's spectral distribution on the characteristic of corresponding sampling harmnoics is demonstrated.(3)Different systems based on electro-optical modulation are implemented.First,to realize a PADC system with high sampling speed and high digitalized accuracy,a mathematical model of the channel interleaved scheme based on photonic switch is analyzed and numerically simulated.The figure of merit(Fo M)that affects the demutiplexing performance of electro-optical modulator based photonic switch is derived.In experiment,a dual-output electro-optical modulator based PADC system is constructed.With the adjustment of Fo M's determining factors,the bandwidth and effective number of bits(ENOB)PADC can be optimized.Second,the optical pulse compression reflectometry(OPCR)based on different modulation schemes are studied.The sactering curves of OPCR with single sideband and double sideband modulation are derived,respectively.It is found thet there exists dispersion penalty in double sideband modulation based OPCR system.In experiment,both schems are demonstrated.With the optimization of optical power of echo signal and noise characteristic,a long distance fiber is detected with high resolution.(4)The all-optical signal process in MWP system is studied in theory and experiment.First,the working principle of optical parametric process is emerged into the basic theory of MWP link.Second,the effects of electrical-optical and optical-optical cascades on the performance of MWP are explored.Furthermore,a multi-channel signal processing method based on optical parametric sampling is proposed.The feasibility is verified by a demonstration of radar receiver system based on the method.(5)With the theoretical modeling and key technologies analysis explored above,the research foundation for MWP optimization is established,which is used for system design and application development of MWP.Based on the previous accumulation of theoretical analysis and experimental exploration of PADC,the performance measurement and application demonstration of a PADC prototype are executed.Due to the channel interleaved structure used in the PADC prototype,the channel mismatch mechanism is clarified.The channel mismatch caribration and compensation methods are given for practical application.Furthermore,the PADC prototype is applied to a radar system for signal reception.With the configuration of interleaved channels,the sampling rate of the prototype can be defined.Finally,through the acquisition and processing of wideband radar echo signals at different bands,the detection of targets with high resolution is achieved.