Tube-encased fiber grating

Abstract

A tube-encased fiber grating includes an optical fiber having at least one Bragg grating impressed therein which is embedded within a glass capillary tube . Light is incident on the grating and light is reflected at a reflection wavelength &lgr; . The shape of the tube may be other geometries (e.g., a “dogbone” shape) and/or more than one concentric tube may be used or more than one grating or pair of gratings may be used. The fiber may be doped at least between a pair of gratings , encased in the tube to form a tube-encased compression-tuned fiber laser or the grating or gratings may be constructed as a tunable DFB fiber laser encased in the tube . Also, the tube may have an inner region which is tapered away from the fiber to provide strain relief for the fiber , or the tube may have tapered (or fluted) sections which have an outer geometry that decreases down to the fiber and provides added fiber pull strength. Also, the tube-encased grating exhibits lower mode coupling from the fiber core to the cladding modes due to the increased diameter of the cladding where the tube is fused to the fiber where the grating is located