Optical switch based on a fluid-filled photonic crystal fiber Bragg grating

We report the implementation of an in-fiber optical switch by means of filling a fluid into the air holes of a photonic crystal fiber with a fiber Bragg grating. Such a switch can turn on/off light transmission with an extinction ratio of up to 33 dB within a narrow wavelength range (Bragg wavelength) via a small temperature adjustment of +/-5 degrees C. The switching function is based on the temperature-dependent coupling between the fundamental core mode and the rod modes in the fluid-filled holes resulting from the thermo-optic effect of the filled fluid.