Q-value Research Of The Microwave Photonic Filter Based On FBGs

Microwave Photonic Filter (MPF) is widely used in kinds of communication domain, thanks to the numerous advantages such as high bandwidth, low loss, and immunity to electromagnetic interference. The FBGs have been considered a good candidate for the microwave filtering because of the excellent property of wavelength choosing and controllability. The Q-value represents the quality of frequency choosing, which is one of the most important factors to measure the character of MPF.The main work of this paper is to analyze the influence to Q-value of MPF, which is based on the structure of FBGs. The main points are as follows:1. Analyzing the theory of MPF based on the structure of FBGs, and the character of wavelength filtering of the FBGs is also analyzed. Besides, the factors which influence the quality of MPF are got.2. The influence of the pole and order to the Q-value in the transform function is been theoretically analyzed. The conclusion is that the Q-value could be improved by increase order of the function. Besides, better results can be got through making the pole of the function approach to the unit circle.3. The high-Q MPF based on first-order, second-order and third-order of function of MPF are analyzed through the way of signal flow chart. Also, the results prove that increasing the value of order can improve the Q-value, but it is limited by other structure parameters. Moreover, a kind of MPF based on the connected structure between Fiber Bragg Gratings and Mach-Zehnder Interferometer is proposed and analyzed, which has high Q-value.4. A new structure of MPF is proposed and analyzed through signal flow chart.5. The new way of implementation in tunable MPF and negative coefficients MPF is discussed. Also, the tunable MPF based on array lasers and dispersion fiber is manipulated. The result shows that increasing the number of laser can improve the Q-value. Besides, the negative coefficients MPF based on two electronic modulators which are driven at different opposing bias points is analyzed, and it proves that the better results can be got when the couple coefficient and gain of EDFA (Erbium-Doped Fiber Amplifier) is set up appropriately.