Abstract: An optical system for selectively filtering and modulating light transmitted through an optical fiber. A tunable optical filter is provided which is capable of selectively correcting, amplifying or modulating light within an optical fiber by selectively extracting light from the core of the fiber into the cladding where it may be acted upon using an active device. Where the active device includes an electrically sensitive material, a constant or varying voltage applied to the material causes the refractive index of the material to change, affecting the transmission of the light within the fiber. Various combinations of gratings and electrically driven elements can be combined to provide various types of filters, amplifiers, modulators and delay lines that are easily incorporated into an optical fiber line.

Abstract: A grating is induced in the core of a hydrogen-loaded high-germanium-content optical fiber using near-UV (275 nm-390 nm) laser light. An interference is generated at the core using a molded polymer phase mask with a square wave surface relief pattern. The light is directed through the phase mask, through a protective fiber coating, through the cladding, and into the core. The phase mask generates an interference pattern with a period half that of the surface relief pattern. Index of refraction changes occur at the bright fringes of the interference pattern--thus creating the grating. Advantages over existing mid-UV technology include lower fabrication costs for phase masks, simplified grating induction since fiber coatings do not need to be removed, and reduced infrared absorption caused by grating formation fiber.

Abstract: A grating is induced in the core of a hydrogen-loaded high-germanium-content optical fiber using near-UV (275 nm-390 nm) laser light. An interference pattern is generated at the core using a molded polymer phase mask with a square wave surface relief pattern. The light is directed through the phase mask, through a protective fiber coating, through the cladding, and into the core. The phase mask generates an interference pattern with a period half that of the surface relief pattern. Index of refraction changes occur at the bright fringes of the interference pattern--thus creating the grating. Advantages over existing mid-UV technology include lower fabrication costs for phase masks, simplified grating induction since fiber coatings do not need to be removed, and reduced infrared absorption caused by grating formation in the fiber.