Research On Microwave Photonic Filter Based On Cascaded Dispersion Devicc

Compared with traditional methods of electronic signal processing, microwave photonicfilter has the function of tuning and reconfigurability in addition to the advantages of low loss,high bandwidth and immunity to electromagnetic interference. With the expansion ofmicrowave photonic filter application field, the requirements for high performance of filtersare increasing, among which a high quality factor(Q), reconfigurability, tenability and flatcharacteristics are research focuses.Two aspects of filter, a high Q value and a flat characteristic respectively, are studied inthis paper. The main contents are as follows:(1) The microwave photonic system and its application prospects are introduced briefly,and the research and application of microwave photonic filters are elaborated. At last theresearch situation of multi-wavelength fiber laser is presented.(2) The basic principles and classification of microwave photonic filters are given, andthe basic principles of finite and infinite response filter are analyzed. At the same time, thebasic principle of microwave photonic filter which is cascaded by finite and infinite responseis analyzed.(3) The negative coefficient microwave photonic band-pass filter with dispersion devicescascading is proposed. Selecting Multi-wavelength fiber laser as light source, and the Sagnacinterferometer is used to shape the output signal, reconfigurability of filter is achieved. Thenarrowband and high frequency selectivity of filter is achieved by cascading single modefiber and fiber delay loop. The simulation results show that after the cascading, the bandwidth,quality factor and main side lobe suppression ratio of filter have been improved greatly.(4) Two types of microwave photonic filter with a flat characteristic based on cascade ofdispersion devices are proposed. One is cascaded by two-tap FIR filter and IIR filter, thedelay units of which are MZ interferometer and FBG respectively. The other is similar to thefirst one in structure, but the IIR filter is based on fiber delay loop. By adjusting the keyparameter of IIR filter and FIR filter, the peaks and troughs of two filters can compensateeach other so as to realize the intermodulation of band-pass and band-stop.