Tilted Moiré Fiber Bragg Grating Optical Filters With Controllable Passband and Stopband

Controllable passband and stopband optical filters based on tilted moire fiber Bragg gratings (FBGs) are presented. The gratings are formed by combining two FBGs of equal period, with one of them tilted at a small angle with respect to the fiber axis. The spectral response consists of the phase-shifted, narrow resonance-dip main peak, and the discrete cladding modes. In this paper, we systematically and experimentally investigated the spectral characteristics of tilted moire FBGs. Experimental results demonstrated that, upon changing the tilt angle and grating length in different combinations, the grating and resonance-dip bandwidths, and the cladding modes characteristics, can be controlled and modified. These features enable the flexible design of optical filters with controllable passband and stopband.