Research Of Tunable Bandpass Microwave Photonic Filter

With the widely application of modern communication technology in various fields,people’s degree of dependence for communication capacity is also increasing. Microwave photonics, a interdisciplinary field between microwave and optical signals, has broad application prospects in fiber optic wireless communication systems, broadband access networks, sensor networks and other fields, so it has got rapid development in recent years.Microwave photonic filter integrates microwave devices and photonic devices to realize the process of high frequency microwave signals in optical domain. Not only can it overcome the defects of the traditional microwave communication, but also keep optical fiber communication advantages of high bandwidth, high sample rate, low loss and anti electromagnetic interference etc. On the other hand, the simple tunable characteristic is a bright spot. It means that the filter can realize filtering of different frequency microwave signal without changing the filter structure. This paper mainly design three kinds of realization schemes of tunable bandpass microwave photonic filter, and verify the filtering characteristics of tunable filter bandpass microwave photonic filter by simulation and related experiments.The main research contents are as follows:First, the thesis introduces the development background of microwave photonic filter,working principle and research situation at home and abroad. A detailed analysis of the theoretical basis of microwave photonic filter based on phase modulator is given and we separately elaborated the PM-IM conversion principle based on single mode fiber and stimulated brillouin scattering effect.Second, with Gauss wide spectrum light source used as optical carrier, we take advantage of the continuous cutting characteristics of MZI to get continuous sinusoidal distribution optical taps. Then we present a new design scheme single-passband tunable photonic microwave filter based on the MZI.The passband tuning scope of filter has been obviously enlarged, and it effectively improves the turning range of the passband.Third, the paper puts forward a new scheme of high Q value frequency hopping bandpass microwave photonic filter. We analysis the changes of cascaded filters’ frequency hopping features with related quantities. The conclusion shows that microwave photonic filter based on the principle can realize hopping in the center frequency of filter by changing the polarization state of controller with a reasonable design of length and number of polarization maintaining fiber.Fourth, with the use of stimulated brillouin scattering effect in a single mode fiber to break the amplitude balance of phase modulation, thus completing the PM-IM conversion.Through the detect from photoelectric detector,the filter has very good tuning characteristics,which is able to realize a tuning range from 1.2G to 9.7GHz.