Research Of Switchable Microwave Photonic Filter Based On Phase Modulation

The rapid development of microwave electronics,photonics and ultra-fast optics has led to a new field microwave photonics.Microwave photonics can be defined as the study of photonic devices in microwave or millimeter-wave or even terahertz wavebands and their applications in microwave or photonic systems.Since the advent of microwave photonics in the late 1970 s,this field has expanded rapidly and has produced many important commercial applications.In the field of the multidisciplinary cross,the typical research includes superfast signal measurement,high speed microwave signal,signal process and transformation,microwave signal rely on broadband optical link for distribution and transmission,etc.Microwave photonic filter is a photonic system which has the same function in comparison to the traditional microwave filter.It processes microwave and millimeterwave signal by using photonic devices eliminating the "electronic bottleneck" of traditional microwave filter,it has the advantages of low loss,high bandwidth,antielectromagnetic interference,tunability and reconfigurability etc.With the rapid development of broadband wireless access networks,the demand of communication systems for capacity and rate is higher and higher,so microwave photonic filter for signal process has attracted more and more attention from researchers,at the same time,microwave photonic filter has the specific application in radar and optical control technology of phased array antenna.According to the current development trend,this paper studied the technology of switchable microwave photonic filter,it mainly includes the following aspects:(1)We studied the experimental method of various kinds of microwave photonic filters,the basic principle and realization technology of the microwave photonic filter are introduced systematically,it established the theoretical basis of our paper.(2)We proposed and experimentally demonstrated a microwave photonic filter based on cascaded Sagnac loop structure cutting broadband optical source,by adjusting the polarization controller within the Sagnac loop,we can change the cycles of comb spectrum,which combined with the mechanism of phase modulator and the dispersion compensation fiber make the microwave photonic filter frequency response curve can be switched in a single passband state,dual-passband state and triple-passband state.(3)We proposed and experimentally demonstrated a switchable microwave photonic filter between bandpass and notch filter using the polarization dependence principle of stimulated Brillouin scattering in the fiber.The gain area of the stimulated Brillouin scattering amplifies the amplitude of modulation sideband,the corresponding polarization angle of modulation sideband will be rotated.By adjusting the polarization angle of the pump light and coupling with phase modulator and dispersion-shifted fiber,a bandpass response and notch response can be switched flexibly...