Fiber Fabry-Perot interferometer with mode-converting Bragg gratings

Bragg gratings are genuine narrow band reflectors. However, for several applications narrow band transmission filters are of interest. It is demonstrated that a pair of mode-converting Bragg gratings in a Fabry-Perot interferometer configuration yields a nonreflecting, narrow-band transmission filter. A more detailed investigation shows further a different mode of operation where narrow band reflection occurs in resonance. It is shown experimentally how both modes of operation are attained by UV trimming of the Fabry-Perot interferometer. A mathematical model for the mode-converting Fabry-Perot interferometer is given.