Fluid-filled microstructured optical fibers and switching applications

We filled a refractive index matching liquid into the air holes of a Ge-doped solid-core microstructured optical fiber (MOF) with a fiber Bragg grating (FBG) to investigate its switching functions. A type of thermo-optic in-fiber switch based on the tunable bandgap effect was demonstrated in the fluid-filled FBG at the Bragg wavelength of 830nm, and its extinction ratio depends strongly on the reflectivity of the FBG. Another type of optical switch with an extinction ratio of 30 dB was developed in the fluid-filled MOF at a long wavelength of 1200 or 1400nm, attributing to the absorption of the filled liquid. Such two types of switches can turn on/off the light transmission via a small temperature adjustment of ±5 or ±10oC, respectively, and will find useful applications in all-fiber optical communication systems.