Tunable Single-Passband Microwave Photonic Filter And Its Application

In recent years, microwave photonic filter(MPF) has become a hot research topic. Compared to the electric field of microwave filters, MPF has many advantages like wide bandwidth, light weight, resistance to electromagnetic interference, tunablity and reconfigurablity and so on. what’s more it has good compatibility with optical fiber transmission system. In radar and satellite communication, broadband wireless access network, sensor network, MPF has wide applications in these fields. So far, pepple have put forward a variety of structures of MPF, however the MPFs usually use the discrete time sampling, the frequency response is often periodic. It causes that the free spectral range(FSR) is small. Although the method of using cascade can expand the FSR,however, the filter periodic frequency response problems still exist, and the structure is complex.But single passband MPF can overcome this problem. The main content of this article is:1.A single passband microwave photonic filter based on the series of fiber Bragg grating(FBG)is proposed. Firstly,the spectrum of a series of FBGs is calculated theoretically. Then according to the principle of phase modulation-intensity modulation conversion,the simulation of this microwave photonic filter’s frequency response. By stretching the FBG, the reflection spectrum of the center frequency is turned. Finally, the filter with turnable bandwidth is realized.2.A single passband MPF based on two groups of the series FBGs is proposed. By tuning the center frequency of one group of FBGs’ reflection spectrum, the change of the reflection spectrum’s bandwidth is realized. Finally, the filter with tunable bandwidth and center frequency is achieved.3.A single passband MPF based on the chirped phase-shifted fiber Bragg grating(PS-FBG).The reflection spectrum of ordinary PS-FBG and the frequency response of the single passband MPF are carried on the theoretical and experimental research. Adjusting the wavelength of tunable laser source can realize a tunable single pass band MPF.4.The single passband MPF based on the chirped phase-shifted fiber Bragg grating is applied to the optoelectronic oscillator(OEO). Firstly, theoretical analysis of the OEO is carried on, then the spectral response of the OEO is undergo the theoretical calculation and simulation.Finally, by tuning the wavelength of the light source, a frequency tunable OEO is achieved.