Study On Novel Multi-passband Microwave Photonic Filter

In the rapid development of information technology in recent decades,microwave photonics has received keen attention and extensive research from academics and practical companies.Microwave photonics is a new interdisciplinary discipline that combines the advantages of both optoelectronics and microwave technology.The combination of superiorities of optical technology and electrical technology has allowed the system to be upgraded and optimized.With the advent of the information era,the demand for high-speed and large-capacity communication system is increasing,and microwave photonic technology will play an important role in the fields of optical fiber communications,sensor networks,and radar satellite communications.This thesis mainly studies different types of microwave photonic filters and their practical applications in fiber optic sensing systems,and both the theoretical analysis and experimental research have been carried out.In this thesis,firstly briefly introduction of the basic concepts,development history,salient features,potential research directions and development prospects of microwave photonic technology have been given.The main components of the microwave photonic filter,structural principles,as well as parameter characteristics,basic types,etc.,are also described in the thesis.Then,the structural design and working principle of the multi-passband microwave photonic filter based on several modified fiber-optic Mach-Zehnder interferometers(FMZI)are analyzed in detail and demonstrated in the experiments.A dual-passband filter based on a reflective FMZI is designed to achieve the switchable and continuous tuning of the passbands.A four-passband filter with cascaded FMZIs is also proposed,which also achieves the switching of different number of pass-bands.Finally,a cascaded reflective FMZIs twelve-passband microwave photonic filter is designed,and the switching and tuning of the passband are also achieved in the experiment.Based on the above analysis and experiment,we summarized the relationship between the number of system stages and the number of pass-bands.Subsequently,the text improved a periodic microwave photonic filter based on a multi-wavelength Erbium-doped fiber laser.A multi-wavelength Erbium-doped fiber laser incorporating a semiconductor optical amplifier is used as the light source of the filter system,and a FMZI structure is added in the laser cavity for wavelength selection,so that the output laser wavelength interval and the number of wavelengths can be tuned.The tuning of the filter's passbands are thus realized,meanwhile the reconfigurability of the filter can be achieved by adjusting polarization controllers and gain of optical amplifiers in the system.Then,the application of microwave photonic filter in sensing is studied.A simultaneous temperature and transversal loading sensing system based on a fiber ring microwave photonic filter is proposed and demonstrated.A temperature and transversal loading sensing system based on a reflective FMZI dual-passband microwave photonic filter has also been studied,and higher sensitivity has been achieved.Finally,summarization and autocriticism are given and future work is discussed.