Design of a microwave photonic filter using phase-shifted FBG-based delay lines and IIR filtering technique for photonic integrated circuits

Abstract An efficient approach for the design of wideband microwave photonic filter (MWPF) using phase-shifted fiber Bragg gratings (FBGs) and the pole-zero placement technique is demonstrated. An infinite impulse response (IIR) filtering framework is employed to significantly reduce the number of filter components. The optimized filter coefficients are constrained to be real and treated as the reflectivities of π -phase-shifted FBGs arranged in a serial feedback configuration. Highpass and bandpass/multi-bandpass MWPF responses are realized over a wide operating frequency range of 0.2–25 GHz. The overall length of the FBG-based filtering link is compact, ranging from 0.4 cm to 8 cm. The cascaded IIR stage has been introduced to improve Q-factor and to achieve single bandpass filter response for wideband application. Theoretical analysis and system-level simulation are in close agreement, confirming the effectiveness of the proposed design methodology. Moreover, the presented microwave photonic filtering scheme is not limited to FBG-based implementations and can be readily extended to integrated waveguide grating platforms for photonic integrated circuit applications.