Analysis for transmission characteristics of multi-cavity fiber Fabry-Perot filters based on fiber Bragg gratings

The all-fiber, multi-cavity, Fabry-Perot passband filters based on fiber Bragg gratings, up to seven, are presented and modeled. The general formulas of the transfer function for the multiple-cavity Fabry-Perot filters are derived with the transfer matrix method. Transmission spectrum characteristics of the filters with different number of cavities are simulated, analyzed and compared. Numerical results show that near-rectangular bandpass shape can be realized by choosing the proper index modulation depths for every forming FBGs. And the simulations clearly demonstrate that the more we increase the number of cavities the more the shape of the central transmission peak is getting rectangular.