Frequency Conversion Based On Microwave Photonics And Photonic Integration

With the rapid development of science and technology,traditional electronic systems cannot meet the growing demand for large bandwidth and high frequency in many fields such as wireless communication systems,satellite communications and radar due to their inherent bottlenecks.Microwave photonics,which is the study of the interaction between microwave technology and photonic technology,can completely make up for the disadvantages of traditional electronic technology.It has gained great attention in the last few decades due to its advantages of large communication capacity,low transmission loss and anti-electromagnetic interference.Frequency up-conversion and down-conversion technologies are indispensable in radar,communication and other fields.The main focus of this paper is the frequency conversion technology based on microwave photonics,combined with photonic integration technology,which is known for its small size,light weight,and low power consumption.The specific research content of this paper is as follows:1.This thesis introduces the advantages of microwave photonics.At the same time,it introduces the photonic integration technology.Then,it summarizes three typical structures of microwave photonic conversion,and briefly analyzes the issues need to be solved.Then,this paper discusses the researching actuality inland and overseas.After that,it lists some core components of microwave photonics,and the modulators and modulation methods are emphasized.Finally,the performance indicators of microwave photonic conversion are described.2.An up-conversion scheme based on a dual-parallel polarization modulator(DP-PolM)and an intensity modulator(IM)is proposed.This scheme uses DP-PolM to modulate the quadrature local oscillator signal,IM is cascaded to DP-PolM,which loaded with the radio frequency signal.Finally,we can get an upconverted signal with frequency doubling is generated.This scheme can be transmitted via optical fiber and it is immune to chromatic dispersion-induced power fading.The structure of this scheme is simple.In simulation,the spur suppression ratio is 32.2dB,the conversion efficiency is stable at about-25.9dB,and the spurious-free dynamic range is 113.6dB·Hz2/3.The scheme does not use filters,so it has good tunable performance.What's more,the components it used are not complicated,so it is possible to integrate the whole system on one chip.3.An image-reject microwave photonic downconverter based on cascaded Sagnac loop and IM is proposed.This scheme uses IM1 in the Sagnac loop to modulate the local oscillator signal,IM2 is cascaded to the Sagnac loop,which loaded with the radio frequency signal.We use an optical bandpass filter to filter out the upper sideband of the polarization multiplexed signal.After a 90° optical hybrid,quadrature intermediate frequency(IF)signals are obtained by two photodetectors.Image rejection is implemented by combining quadrature IF signals via an electrical 90° hybrid coupler.In simulation,the image rejection ratio is about 65 dB,the conversion efficiency is stable at about-25dB,and the spurious-free dynamic range is 113dB·Hz2t3.We get a high-quality down-conversion signal in all-optical approach,and the components after the Sagnac loop can be integrated on one chip.4.An image-reject microwave photonic downconverter based on an optoelectronic oscillator(OEO)is proposed.The local oscillator signal is produced by the OEO.The output signal modulated by DP-PolM is filtered out to two channels through the Waveshaper.After a polarization controller and a polarization beam splitter in each channel,quadrature intermediate frequency(IF)signals are obtained by two photodetectors.Image rejection is implemented by combining quadrature IF signals via an electrical 90° hybrid coupler.This scheme does not require an external local oscillator source.In simulation,the image rejection ratio is more than 50dB,the conversion efficiency is stable at about-30dB,the spurious-free dynamic range is 91.5dB·Hz2/3.When we use the system to transmit vector signal,we can also get high-quality down-conversion signal.What's more,the components after OEO can be integrated on one chip.