Integrated all-fiber variable attenuator based on hybrid microstructure fiber

We present a design for modulating light in a single-mode optical fiber by achieving efficient field interaction between the fundamental mode of an air–silica microstructure optical fiber and tunable materials incorporated in the air holes of the fiber. This method involves tapering microstructure optical fiber where light is guided by the air holes and modulated by a polymer incorporated in these capillary voids. Using this fiber design, we experimentally demonstrate a variable attenuator (loss filter) with 30 dB dynamic range, insertion loss of less than 0.8 dB, and minimal polarization dependence.