Synthesis of Flat-Top Bandpass Filters Using Two-Band Rejection Long-Period Fiber Gratings

We propose a synthesis method based on the genetic algorithm for designing flat-top bandpass filters using two-band rejection long-period fiber grating (LPFG) filters. In the proposed method, the LPFG structure constructed by concatenating the two-band rejection filters is used as the initial parameter to easily design good flat-top bandpass filters in a wavelength range.