A novel bandwidth- and center-wavelength-tunable interleaver structure based on birefringent materials is proposed. This device can provide network designers more flexibility in their design work and reduce system upgrading and modification costs. Since the proposed structure is a kind of finite-impulse-response filter, the interleaver can be designed to be dispersion-free. Moreover, it can be implemented without moving parts to increase reliability. These two features make the proposed device attractive for increasing design flexibility and network efficiency. Simulation and experimental results are presented to verify the fundamental idea.