A band-pass microwave photonic filter based on Lyot-Sagnac filter and cascaded optical structures

Abstract

A band-pass microwave photonic filter (MPF) based on Lyot-Sagnac filter and two cascaded optical structures is demonstrated. In the experiment, a stabilized and tunable multi-wavelength optical source is obtained by slicing the broadband optical source (BOS) with a Lyot-Sagnac filter. A standard single-mode fiber (SMF) and a fiber ring resonator are cascaded to improve the mainlobe-to-sidelobe suppression ratio (MSSR) and Q-factor of the filter. The analysis shows that MSSR and Q-factor are improved by reducing the split ratio of the coupler or increasing the length of fiber in fiber ring resonator. The results have significant guidance for MPF design by choosing appropriate devices and parameters. Based on the analyses, a band-pass filter with MSSR of 53.54 dB and Q-factor of 4048 is achieved by choosing the split ratio of 0.01, the length of SMF of 30 km and the length of fiber in fiber ring resonator of 152.27 cm.