Research On Tunable Microwave Photonic Filter Based On Multi-wavelength Optical Source

Microwave Photonic Filter is a subject which combines Optics and Microwave science.It has the advantage of Optics to overcome the electronic bottleneck of traditional filters and process signal in optical domain.So that the device structure is relatively flexible.MPF has advantages of large bandwidth,tunable and reconfigurability.In this paper,we studies tunable MPF based on multi-wavelength light source.The main contents are as follows.(1)The fundamental principle and application of MPF are enumerated.Different types of MPF are classified.Recent MPF research status and some multi-wavelength light sources which can realize tunable MPF are summarized.(2)Theoretical analysis of basic principle of MPF which based on phase modulation is given and the design methods of tunable MPF are discussed.A brief description of implementation of multi-wavelength light source is presented.(3)A microwave photonic filter based on photonic crystal fiber Sagnac loop is presented,the filter's center frequency can be continuously tunable.The birefringence of PCF can be tuned by adjusting the filling liquid's temperature.So the wavelength spacing of Sagnac loop which has the PCF in it can be tuned,thus using the Sagnac loop to slice the broadband light source,by adjusting the thermo-sensitive liquid's temperature,the center frequency of the microwave photonic filter can be tuned continuously.(4)A microwave photonic filter based on photonic crystal fiber Lyot-Sagnac loop is presented,the filter's center frequency can be continuously tunable.By adjusting the temperature in two PCFs and the polarization controller between them,the tuning range of wavelength spacing which generated by the Lyot-Sagnac loop slicing the broadband light source can be connected,and the wavelength spacing of multi-wavelength light source and center frequency of the microwave photonic filter can be continuously tunable.(5)A microwave photonic filter using a technology of four wave mixing(FWM)is proposed and experimentally demonstrated.Two single-frequency laser beams occur four wave mixing effect in a highly nonlinear fiber(HNLF)and generate multi-wavelength laser output.The wavelength spacing of the multi-wavelength laser equals to the frequency difference of two input laser beams.By changing the frequency difference of two input laser beams,wavelength spacing of the multi-wavelength laser output can be continuously tuned,thus the center frequency of the filter can be tuned continuously too.