Tunable Optical Fiber Filter Based on a Fiber Bragg Grating Loop Mirror

A novel structure and principle of a tunable optical fiber filter is proposed, including a fiber Bragg grating loop mirror, an electromagnetic force based cantilever tuning unit, and a micro-displacement tuning unit. The electromagnetic force based cantilever tuning unit is used to change the pass band of the optical fiber filter, and the micro-displacement tuning unit is used to change the channel spacing of the comb filter within the pass band. The electromagnetic force is produced by an electromagnetic coil and permanent magnet element, and the micro-displacement driver includes a PZT piezoelectric ceramic and its driving circuit. Principles and structures are introduced. Theoretical and experimental results indicate the feasibility of the proposed idea. And some key problems about the cantilever and the PZT structure are discussed.