Research On Microwave Photonic Filters Using Dispersive Fiber

The microwave photonic filters based on dispersive fiber are studied after the introduction of microwave photonics and Radio-over-Fiber (RoF) systems. They are divided into three classes from point of practical view. They are band-notch filters, single-bandpass filters and multi-bandpass filters, respectively. A theoretical mode is established for the first time about the multi-waves microwave photonic filters using dispersive media, and applied to simulate and analyze the different kinds of filters. The influences of different parameters, such as wavelength spacing, 3dB bandwidth of the peak, mismatch of the peaks and the length of the fiber, on the filters' RF response are carefully studied, and some collusion is achievedThe relationships of the bandwidth of sidelobes and main peaks of the response of microwave photonic filters using lasers array, and the number of the sidelobes within a period and the lasers' have been discovered for the first time as far as we know. Further more, the relationship between the FSR and wavelength spacing is studied, and the experimental results are in well agreement with the theoretical predictions.The microwave photonic filters using Mach-Zehnder interferometer (MZI) is proved to be a single bandpass filter for the transmission spectrum of the MZI could be expressed as a continuous function. A continuous tunable single-bandpass filters using computer controlled optical delay line is experimentally demonstrated, with its tuning range between 34.1MHz and 34.1 GHz.Superstructured fiber Bragg grating (SFBG) is especially attractive to microwave photonic filters, because it could create a precise comb of weighted optical peaks which are all modulated by the same microwave signal. The reflective spectrum of SFBG has been achieved numerical simulations according to the transfer matrix theory. A SFBG with the optical peaks spacing of 1nm is fabricated and used to realize a multi-bandpass filter.